Google Git
Sign in
cobalt / cobalt / 5b531220b4e0f9dbaf2334d084ae89c84c7afe2a / . / src / third_party / sqlite / src / src / where.c
blob: cf30d94d671bb81ef361cb6ac5b7a1aae392f395 [file] [log] [blame]
/*
** 2001 September 15
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
*************************************************************************
** This module contains C code that generates VDBE code used to process
** the WHERE clause of SQL statements. This module is responsible for
** generating the code that loops through a table looking for applicable
** rows. Indices are selected and used to speed the search when doing
** so is applicable. Because this module is responsible for selecting
** indices, you might also think of this module as the "query optimizer".
*/
#include "sqliteInt.h"
/*
** Trace output macros
*/
#if defined(SQLITE_TEST) || defined(SQLITE_DEBUG)
int sqlite3WhereTrace = 0;
#endif
#if defined(SQLITE_TEST) && defined(SQLITE_DEBUG)
# define WHERETRACE(X) if(sqlite3WhereTrace) sqlite3DebugPrintf X
#else
# define WHERETRACE(X)
#endif
/* Forward reference
*/
typedef struct WhereClause WhereClause;
typedef struct WhereMaskSet WhereMaskSet;
typedef struct WhereOrInfo WhereOrInfo;
typedef struct WhereAndInfo WhereAndInfo;
typedef struct WhereCost WhereCost;
/*
** The query generator uses an array of instances of this structure to
** help it analyze the subexpressions of the WHERE clause. Each WHERE
** clause subexpression is separated from the others by AND operators,
** usually, or sometimes subexpressions separated by OR.
**
** All WhereTerms are collected into a single WhereClause structure.
** The following identity holds:
**
** WhereTerm.pWC->a[WhereTerm.idx] == WhereTerm
**
** When a term is of the form:
**
** X <op> <expr>
**
** where X is a column name and <op> is one of certain operators,
** then WhereTerm.leftCursor and WhereTerm.u.leftColumn record the
** cursor number and column number for X. WhereTerm.eOperator records
** the <op> using a bitmask encoding defined by WO_xxx below. The
** use of a bitmask encoding for the operator allows us to search
** quickly for terms that match any of several different operators.
**
** A WhereTerm might also be two or more subterms connected by OR:
**
** (t1.X <op> <expr>) OR (t1.Y <op> <expr>) OR ....
**
** In this second case, wtFlag as the TERM_ORINFO set and eOperator==WO_OR
** and the WhereTerm.u.pOrInfo field points to auxiliary information that
** is collected about the
**
** If a term in the WHERE clause does not match either of the two previous
** categories, then eOperator==0. The WhereTerm.pExpr field is still set
** to the original subexpression content and wtFlags is set up appropriately
** but no other fields in the WhereTerm object are meaningful.
**
** When eOperator!=0, prereqRight and prereqAll record sets of cursor numbers,
** but they do so indirectly. A single WhereMaskSet structure translates
** cursor number into bits and the translated bit is stored in the prereq
** fields. The translation is used in order to maximize the number of
** bits that will fit in a Bitmask. The VDBE cursor numbers might be
** spread out over the non-negative integers. For example, the cursor
** numbers might be 3, 8, 9, 10, 20, 23, 41, and 45. The WhereMaskSet
** translates these sparse cursor numbers into consecutive integers
** beginning with 0 in order to make the best possible use of the available
** bits in the Bitmask. So, in the example above, the cursor numbers
** would be mapped into integers 0 through 7.
**
** The number of terms in a join is limited by the number of bits
** in prereqRight and prereqAll. The default is 64 bits, hence SQLite
** is only able to process joins with 64 or fewer tables.
*/
typedef struct WhereTerm WhereTerm;
struct WhereTerm {
Expr *pExpr; /* Pointer to the subexpression that is this term */
int iParent; /* Disable pWC->a[iParent] when this term disabled */
int leftCursor; /* Cursor number of X in "X <op> <expr>" */
union {
int leftColumn; /* Column number of X in "X <op> <expr>" */
WhereOrInfo *pOrInfo; /* Extra information if eOperator==WO_OR */
WhereAndInfo *pAndInfo; /* Extra information if eOperator==WO_AND */
} u;
u16 eOperator; /* A WO_xx value describing <op> */
u8 wtFlags; /* TERM_xxx bit flags. See below */
u8 nChild; /* Number of children that must disable us */
WhereClause *pWC; /* The clause this term is part of */
Bitmask prereqRight; /* Bitmask of tables used by pExpr->pRight */
Bitmask prereqAll; /* Bitmask of tables referenced by pExpr */
};
/*
** Allowed values of WhereTerm.wtFlags
*/
#define TERM_DYNAMIC 0x01 /* Need to call sqlite3ExprDelete(db, pExpr) */
#define TERM_VIRTUAL 0x02 /* Added by the optimizer. Do not code */
#define TERM_CODED 0x04 /* This term is already coded */
#define TERM_COPIED 0x08 /* Has a child */
#define TERM_ORINFO 0x10 /* Need to free the WhereTerm.u.pOrInfo object */
#define TERM_ANDINFO 0x20 /* Need to free the WhereTerm.u.pAndInfo obj */
#define TERM_OR_OK 0x40 /* Used during OR-clause processing */
#ifdef SQLITE_ENABLE_STAT2
# define TERM_VNULL 0x80 /* Manufactured x>NULL or x<=NULL term */
#else
# define TERM_VNULL 0x00 /* Disabled if not using stat2 */
#endif
/*
** An instance of the following structure holds all information about a
** WHERE clause. Mostly this is a container for one or more WhereTerms.
*/
struct WhereClause {
Parse *pParse; /* The parser context */
WhereMaskSet *pMaskSet; /* Mapping of table cursor numbers to bitmasks */
Bitmask vmask; /* Bitmask identifying virtual table cursors */
u8 op; /* Split operator. TK_AND or TK_OR */
int nTerm; /* Number of terms */
int nSlot; /* Number of entries in a[] */
WhereTerm *a; /* Each a[] describes a term of the WHERE cluase */
#if defined(SQLITE_SMALL_STACK)
WhereTerm aStatic[1]; /* Initial static space for a[] */
#else
WhereTerm aStatic[8]; /* Initial static space for a[] */
#endif
};
/*
** A WhereTerm with eOperator==WO_OR has its u.pOrInfo pointer set to
** a dynamically allocated instance of the following structure.
*/
struct WhereOrInfo {
WhereClause wc; /* Decomposition into subterms */
Bitmask indexable; /* Bitmask of all indexable tables in the clause */
};
/*
** A WhereTerm with eOperator==WO_AND has its u.pAndInfo pointer set to
** a dynamically allocated instance of the following structure.
*/
struct WhereAndInfo {
WhereClause wc; /* The subexpression broken out */
};
/*
** An instance of the following structure keeps track of a mapping
** between VDBE cursor numbers and bits of the bitmasks in WhereTerm.
**
** The VDBE cursor numbers are small integers contained in
** SrcList_item.iCursor and Expr.iTable fields. For any given WHERE
** clause, the cursor numbers might not begin with 0 and they might
** contain gaps in the numbering sequence. But we want to make maximum
** use of the bits in our bitmasks. This structure provides a mapping
** from the sparse cursor numbers into consecutive integers beginning
** with 0.
**
** If WhereMaskSet.ix[A]==B it means that The A-th bit of a Bitmask
** corresponds VDBE cursor number B. The A-th bit of a bitmask is 1<<A.
**
** For example, if the WHERE clause expression used these VDBE
** cursors: 4, 5, 8, 29, 57, 73. Then the WhereMaskSet structure
** would map those cursor numbers into bits 0 through 5.
**
** Note that the mapping is not necessarily ordered. In the example
** above, the mapping might go like this: 4->3, 5->1, 8->2, 29->0,
** 57->5, 73->4. Or one of 719 other combinations might be used. It
** does not really matter. What is important is that sparse cursor
** numbers all get mapped into bit numbers that begin with 0 and contain
** no gaps.
*/
struct WhereMaskSet {
int n; /* Number of assigned cursor values */
int ix[BMS]; /* Cursor assigned to each bit */
};
/*
** A WhereCost object records a lookup strategy and the estimated
** cost of pursuing that strategy.
*/
struct WhereCost {
WherePlan plan; /* The lookup strategy */
double rCost; /* Overall cost of pursuing this search strategy */
Bitmask used; /* Bitmask of cursors used by this plan */
};
/*
** Bitmasks for the operators that indices are able to exploit. An
** OR-ed combination of these values can be used when searching for
** terms in the where clause.
*/
#define WO_IN 0x001
#define WO_EQ 0x002
#define WO_LT (WO_EQ<<(TK_LT-TK_EQ))
#define WO_LE (WO_EQ<<(TK_LE-TK_EQ))
#define WO_GT (WO_EQ<<(TK_GT-TK_EQ))
#define WO_GE (WO_EQ<<(TK_GE-TK_EQ))
#define WO_MATCH 0x040
#define WO_ISNULL 0x080
#define WO_OR 0x100 /* Two or more OR-connected terms */
#define WO_AND 0x200 /* Two or more AND-connected terms */
#define WO_NOOP 0x800 /* This term does not restrict search space */
#define WO_ALL 0xfff /* Mask of all possible WO_* values */
#define WO_SINGLE 0x0ff /* Mask of all non-compound WO_* values */
/*
** Value for wsFlags returned by bestIndex() and stored in
** WhereLevel.wsFlags. These flags determine which search
** strategies are appropriate.
**
** The least significant 12 bits is reserved as a mask for WO_ values above.
** The WhereLevel.wsFlags field is usually set to WO_IN|WO_EQ|WO_ISNULL.
** But if the table is the right table of a left join, WhereLevel.wsFlags
** is set to WO_IN|WO_EQ. The WhereLevel.wsFlags field can then be used as
** the "op" parameter to findTerm when we are resolving equality constraints.
** ISNULL constraints will then not be used on the right table of a left
** join. Tickets #2177 and #2189.
*/
#define WHERE_ROWID_EQ 0x00001000 /* rowid=EXPR or rowid IN (...) */
#define WHERE_ROWID_RANGE 0x00002000 /* rowid<EXPR and/or rowid>EXPR */
#define WHERE_COLUMN_EQ 0x00010000 /* x=EXPR or x IN (...) or x IS NULL */
#define WHERE_COLUMN_RANGE 0x00020000 /* x<EXPR and/or x>EXPR */
#define WHERE_COLUMN_IN 0x00040000 /* x IN (...) */
#define WHERE_COLUMN_NULL 0x00080000 /* x IS NULL */
#define WHERE_INDEXED 0x000f0000 /* Anything that uses an index */
#define WHERE_NOT_FULLSCAN 0x100f3000 /* Does not do a full table scan */
#define WHERE_IN_ABLE 0x000f1000 /* Able to support an IN operator */
#define WHERE_TOP_LIMIT 0x00100000 /* x<EXPR or x<=EXPR constraint */
#define WHERE_BTM_LIMIT 0x00200000 /* x>EXPR or x>=EXPR constraint */
#define WHERE_BOTH_LIMIT 0x00300000 /* Both x>EXPR and x<EXPR */
#define WHERE_IDX_ONLY 0x00800000 /* Use index only - omit table */
#define WHERE_ORDERBY 0x01000000 /* Output will appear in correct order */
#define WHERE_REVERSE 0x02000000 /* Scan in reverse order */
#define WHERE_UNIQUE 0x04000000 /* Selects no more than one row */
#define WHERE_VIRTUALTABLE 0x08000000 /* Use virtual-table processing */
#define WHERE_MULTI_OR 0x10000000 /* OR using multiple indices */
#define WHERE_TEMP_INDEX 0x20000000 /* Uses an ephemeral index */
/*
** Initialize a preallocated WhereClause structure.
*/
static void whereClauseInit(
WhereClause *pWC, /* The WhereClause to be initialized */
Parse *pParse, /* The parsing context */
WhereMaskSet *pMaskSet /* Mapping from table cursor numbers to bitmasks */
){
pWC->pParse = pParse;
pWC->pMaskSet = pMaskSet;
pWC->nTerm = 0;
pWC->nSlot = ArraySize(pWC->aStatic);
pWC->a = pWC->aStatic;
pWC->vmask = 0;
}
/* Forward reference */
static void whereClauseClear(WhereClause*);
/*
** Deallocate all memory associated with a WhereOrInfo object.
*/
static void whereOrInfoDelete(sqlite3 *db, WhereOrInfo *p){
whereClauseClear(&p->wc);
sqlite3DbFree(db, p);
}
/*
** Deallocate all memory associated with a WhereAndInfo object.
*/
static void whereAndInfoDelete(sqlite3 *db, WhereAndInfo *p){
whereClauseClear(&p->wc);
sqlite3DbFree(db, p);
}
/*
** Deallocate a WhereClause structure. The WhereClause structure
** itself is not freed. This routine is the inverse of whereClauseInit().
*/
static void whereClauseClear(WhereClause *pWC){
int i;
WhereTerm *a;
sqlite3 *db = pWC->pParse->db;
for(i=pWC->nTerm-1, a=pWC->a; i>=0; i--, a++){
if( a->wtFlags & TERM_DYNAMIC ){
sqlite3ExprDelete(db, a->pExpr);
}
if( a->wtFlags & TERM_ORINFO ){
whereOrInfoDelete(db, a->u.pOrInfo);
}else if( a->wtFlags & TERM_ANDINFO ){
whereAndInfoDelete(db, a->u.pAndInfo);
}
}
if( pWC->a!=pWC->aStatic ){
sqlite3DbFree(db, pWC->a);
}
}
/*
** Add a single new WhereTerm entry to the WhereClause object pWC.
** The new WhereTerm object is constructed from Expr p and with wtFlags.
** The index in pWC->a[] of the new WhereTerm is returned on success.
** 0 is returned if the new WhereTerm could not be added due to a memory
** allocation error. The memory allocation failure will be recorded in
** the db->mallocFailed flag so that higher-level functions can detect it.
**
** This routine will increase the size of the pWC->a[] array as necessary.
**
** If the wtFlags argument includes TERM_DYNAMIC, then responsibility
** for freeing the expression p is assumed by the WhereClause object pWC.
** This is true even if this routine fails to allocate a new WhereTerm.
**
** WARNING: This routine might reallocate the space used to store
** WhereTerms. All pointers to WhereTerms should be invalidated after
** calling this routine. Such pointers may be reinitialized by referencing
** the pWC->a[] array.
*/
static int whereClauseInsert(WhereClause *pWC, Expr *p, u8 wtFlags){
WhereTerm *pTerm;
int idx;
testcase( wtFlags & TERM_VIRTUAL ); /* EV: R-00211-15100 */
if( pWC->nTerm>=pWC->nSlot ){
WhereTerm *pOld = pWC->a;
sqlite3 *db = pWC->pParse->db;
pWC->a = sqlite3DbMallocRaw(db, sizeof(pWC->a[0])*pWC->nSlot*2 );
if( pWC->a==0 ){
if( wtFlags & TERM_DYNAMIC ){
sqlite3ExprDelete(db, p);
}
pWC->a = pOld;
return 0;
}
memcpy(pWC->a, pOld, sizeof(pWC->a[0])*pWC->nTerm);
if( pOld!=pWC->aStatic ){
sqlite3DbFree(db, pOld);
}
pWC->nSlot = sqlite3DbMallocSize(db, pWC->a)/sizeof(pWC->a[0]);
}
pTerm = &pWC->a[idx = pWC->nTerm++];
pTerm->pExpr = p;
pTerm->wtFlags = wtFlags;
pTerm->pWC = pWC;
pTerm->iParent = -1;
return idx;
}
/*
** This routine identifies subexpressions in the WHERE clause where
** each subexpression is separated by the AND operator or some other
** operator specified in the op parameter. The WhereClause structure
** is filled with pointers to subexpressions. For example:
**
** WHERE a=='hello' AND coalesce(b,11)<10 AND (c+12!=d OR c==22)
** \________/ \_______________/ \________________/
** slot[0] slot[1] slot[2]
**
** The original WHERE clause in pExpr is unaltered. All this routine
** does is make slot[] entries point to substructure within pExpr.
**
** In the previous sentence and in the diagram, "slot[]" refers to
** the WhereClause.a[] array. The slot[] array grows as needed to contain
** all terms of the WHERE clause.
*/
static void whereSplit(WhereClause *pWC, Expr *pExpr, int op){
pWC->op = (u8)op;
if( pExpr==0 ) return;
if( pExpr->op!=op ){
whereClauseInsert(pWC, pExpr, 0);
}else{
whereSplit(pWC, pExpr->pLeft, op);
whereSplit(pWC, pExpr->pRight, op);
}
}
/*
** Initialize an expression mask set (a WhereMaskSet object)
*/
#define initMaskSet(P) memset(P, 0, sizeof(*P))
/*
** Return the bitmask for the given cursor number. Return 0 if
** iCursor is not in the set.
*/
static Bitmask getMask(WhereMaskSet *pMaskSet, int iCursor){
int i;
assert( pMaskSet->n<=(int)sizeof(Bitmask)*8 );
for(i=0; i<pMaskSet->n; i++){
if( pMaskSet->ix[i]==iCursor ){
return ((Bitmask)1)<<i;
}
}
return 0;
}
/*
** Create a new mask for cursor iCursor.
**
** There is one cursor per table in the FROM clause. The number of
** tables in the FROM clause is limited by a test early in the
** sqlite3WhereBegin() routine. So we know that the pMaskSet->ix[]
** array will never overflow.
*/
static void createMask(WhereMaskSet *pMaskSet, int iCursor){
assert( pMaskSet->n < ArraySize(pMaskSet->ix) );
pMaskSet->ix[pMaskSet->n++] = iCursor;
}
/*
** This routine walks (recursively) an expression tree and generates
** a bitmask indicating which tables are used in that expression
** tree.
**
** In order for this routine to work, the calling function must have
** previously invoked sqlite3ResolveExprNames() on the expression. See
** the header comment on that routine for additional information.
** The sqlite3ResolveExprNames() routines looks for column names and
** sets their opcodes to TK_COLUMN and their Expr.iTable fields to
** the VDBE cursor number of the table. This routine just has to
** translate the cursor numbers into bitmask values and OR all
** the bitmasks together.
*/
static Bitmask exprListTableUsage(WhereMaskSet*, ExprList*);
static Bitmask exprSelectTableUsage(WhereMaskSet*, Select*);
static Bitmask exprTableUsage(WhereMaskSet *pMaskSet, Expr *p){
Bitmask mask = 0;
if( p==0 ) return 0;
if( p->op==TK_COLUMN ){
mask = getMask(pMaskSet, p->iTable);
return mask;
}
mask = exprTableUsage(pMaskSet, p->pRight);
mask |= exprTableUsage(pMaskSet, p->pLeft);
if( ExprHasProperty(p, EP_xIsSelect) ){
mask |= exprSelectTableUsage(pMaskSet, p->x.pSelect);
}else{
mask |= exprListTableUsage(pMaskSet, p->x.pList);
}
return mask;
}
static Bitmask exprListTableUsage(WhereMaskSet *pMaskSet, ExprList *pList){
int i;
Bitmask mask = 0;
if( pList ){
for(i=0; i<pList->nExpr; i++){
mask |= exprTableUsage(pMaskSet, pList->a[i].pExpr);
}
}
return mask;
}
static Bitmask exprSelectTableUsage(WhereMaskSet *pMaskSet, Select *pS){
Bitmask mask = 0;
while( pS ){
mask |= exprListTableUsage(pMaskSet, pS->pEList);
mask |= exprListTableUsage(pMaskSet, pS->pGroupBy);
mask |= exprListTableUsage(pMaskSet, pS->pOrderBy);
mask |= exprTableUsage(pMaskSet, pS->pWhere);
mask |= exprTableUsage(pMaskSet, pS->pHaving);
pS = pS->pPrior;
}
return mask;
}
/*
** Return TRUE if the given operator is one of the operators that is
** allowed for an indexable WHERE clause term. The allowed operators are
** "=", "<", ">", "<=", ">=", and "IN".
**
** IMPLEMENTATION-OF: R-59926-26393 To be usable by an index a term must be
** of one of the following forms: column = expression column > expression
** column >= expression column < expression column <= expression
** expression = column expression > column expression >= column
** expression < column expression <= column column IN
** (expression-list) column IN (subquery) column IS NULL
*/
static int allowedOp(int op){
assert( TK_GT>TK_EQ && TK_GT<TK_GE );
assert( TK_LT>TK_EQ && TK_LT<TK_GE );
assert( TK_LE>TK_EQ && TK_LE<TK_GE );
assert( TK_GE==TK_EQ+4 );
return op==TK_IN || (op>=TK_EQ && op<=TK_GE) || op==TK_ISNULL;
}
/*
** Swap two objects of type TYPE.
*/
#define SWAP(TYPE,A,B) {TYPE t=A; A=B; B=t;}
/*
** Commute a comparison operator. Expressions of the form "X op Y"
** are converted into "Y op X".
**
** If a collation sequence is associated with either the left or right
** side of the comparison, it remains associated with the same side after
** the commutation. So "Y collate NOCASE op X" becomes
** "X collate NOCASE op Y". This is because any collation sequence on
** the left hand side of a comparison overrides any collation sequence
** attached to the right. For the same reason the EP_ExpCollate flag
** is not commuted.
*/
static void exprCommute(Parse *pParse, Expr *pExpr){
u16 expRight = (pExpr->pRight->flags & EP_ExpCollate);
u16 expLeft = (pExpr->pLeft->flags & EP_ExpCollate);
assert( allowedOp(pExpr->op) && pExpr->op!=TK_IN );
pExpr->pRight->pColl = sqlite3ExprCollSeq(pParse, pExpr->pRight);
pExpr->pLeft->pColl = sqlite3ExprCollSeq(pParse, pExpr->pLeft);
SWAP(CollSeq*,pExpr->pRight->pColl,pExpr->pLeft->pColl);
pExpr->pRight->flags = (pExpr->pRight->flags & ~EP_ExpCollate) | expLeft;
pExpr->pLeft->flags = (pExpr->pLeft->flags & ~EP_ExpCollate) | expRight;
SWAP(Expr*,pExpr->pRight,pExpr->pLeft);
if( pExpr->op>=TK_GT ){
assert( TK_LT==TK_GT+2 );
assert( TK_GE==TK_LE+2 );
assert( TK_GT>TK_EQ );
assert( TK_GT<TK_LE );
assert( pExpr->op>=TK_GT && pExpr->op<=TK_GE );
pExpr->op = ((pExpr->op-TK_GT)^2)+TK_GT;
}
}
/*
** Translate from TK_xx operator to WO_xx bitmask.
*/
static u16 operatorMask(int op){
u16 c;
assert( allowedOp(op) );
if( op==TK_IN ){
c = WO_IN;
}else if( op==TK_ISNULL ){
c = WO_ISNULL;
}else{
assert( (WO_EQ<<(op-TK_EQ)) < 0x7fff );
c = (u16)(WO_EQ<<(op-TK_EQ));
}
assert( op!=TK_ISNULL || c==WO_ISNULL );
assert( op!=TK_IN || c==WO_IN );
assert( op!=TK_EQ || c==WO_EQ );
assert( op!=TK_LT || c==WO_LT );
assert( op!=TK_LE || c==WO_LE );
assert( op!=TK_GT || c==WO_GT );
assert( op!=TK_GE || c==WO_GE );
return c;
}
/*
** Search for a term in the WHERE clause that is of the form "X <op> <expr>"
** where X is a reference to the iColumn of table iCur and <op> is one of
** the WO_xx operator codes specified by the op parameter.
** Return a pointer to the term. Return 0 if not found.
*/
static WhereTerm *findTerm(
WhereClause *pWC, /* The WHERE clause to be searched */
int iCur, /* Cursor number of LHS */
int iColumn, /* Column number of LHS */
Bitmask notReady, /* RHS must not overlap with this mask */
u32 op, /* Mask of WO_xx values describing operator */
Index *pIdx /* Must be compatible with this index, if not NULL */
){
WhereTerm *pTerm;
int k;
assert( iCur>=0 );
op &= WO_ALL;
for(pTerm=pWC->a, k=pWC->nTerm; k; k--, pTerm++){
if( pTerm->leftCursor==iCur
&& (pTerm->prereqRight & notReady)==0
&& pTerm->u.leftColumn==iColumn
&& (pTerm->eOperator & op)!=0
){
if( pIdx && pTerm->eOperator!=WO_ISNULL ){
Expr *pX = pTerm->pExpr;
CollSeq *pColl;
char idxaff;
int j;
Parse *pParse = pWC->pParse;
idxaff = pIdx->pTable->aCol[iColumn].affinity;
if( !sqlite3IndexAffinityOk(pX, idxaff) ) continue;
/* Figure out the collation sequence required from an index for
** it to be useful for optimising expression pX. Store this
** value in variable pColl.
*/
assert(pX->pLeft);
pColl = sqlite3BinaryCompareCollSeq(pParse, pX->pLeft, pX->pRight);
assert(pColl || pParse->nErr);
for(j=0; pIdx->aiColumn[j]!=iColumn; j++){
if( NEVER(j>=pIdx->nColumn) ) return 0;
}
if( pColl && sqlite3StrICmp(pColl->zName, pIdx->azColl[j]) ) continue;
}
return pTerm;
}
}
return 0;
}
/* Forward reference */
static void exprAnalyze(SrcList*, WhereClause*, int);
/*
** Call exprAnalyze on all terms in a WHERE clause.
**
**
*/
static void exprAnalyzeAll(
SrcList *pTabList, /* the FROM clause */
WhereClause *pWC /* the WHERE clause to be analyzed */
){
int i;
for(i=pWC->nTerm-1; i>=0; i--){
exprAnalyze(pTabList, pWC, i);
}
}
#ifndef SQLITE_OMIT_LIKE_OPTIMIZATION
/*
** Check to see if the given expression is a LIKE or GLOB operator that
** can be optimized using inequality constraints. Return TRUE if it is
** so and false if not.
**
** In order for the operator to be optimizible, the RHS must be a string
** literal that does not begin with a wildcard.
*/
static int isLikeOrGlob(
Parse *pParse, /* Parsing and code generating context */
Expr *pExpr, /* Test this expression */
Expr **ppPrefix, /* Pointer to TK_STRING expression with pattern prefix */
int *pisComplete, /* True if the only wildcard is % in the last character */
int *pnoCase /* True if uppercase is equivalent to lowercase */
){
const char *z = 0; /* String on RHS of LIKE operator */
Expr *pRight, *pLeft; /* Right and left size of LIKE operator */
ExprList *pList; /* List of operands to the LIKE operator */
int c; /* One character in z[] */
int cnt; /* Number of non-wildcard prefix characters */
char wc[3]; /* Wildcard characters */
sqlite3 *db = pParse->db; /* Database connection */
sqlite3_value *pVal = 0;
int op; /* Opcode of pRight */
if( !sqlite3IsLikeFunction(db, pExpr, pnoCase, wc) ){
return 0;
}
#ifdef SQLITE_EBCDIC
if( *pnoCase ) return 0;
#endif
pList = pExpr->x.pList;
pLeft = pList->a[1].pExpr;
if( pLeft->op!=TK_COLUMN || sqlite3ExprAffinity(pLeft)!=SQLITE_AFF_TEXT ){
/* IMP: R-02065-49465 The left-hand side of the LIKE or GLOB operator must
** be the name of an indexed column with TEXT affinity. */
return 0;
}
assert( pLeft->iColumn!=(-1) ); /* Because IPK never has AFF_TEXT */
pRight = pList->a[0].pExpr;
op = pRight->op;
if( op==TK_REGISTER ){
op = pRight->op2;
}
if( op==TK_VARIABLE ){
Vdbe *pReprepare = pParse->pReprepare;
int iCol = pRight->iColumn;
pVal = sqlite3VdbeGetValue(pReprepare, iCol, SQLITE_AFF_NONE);
if( pVal && sqlite3_value_type(pVal)==SQLITE_TEXT ){
z = (char *)sqlite3_value_text(pVal);
}
sqlite3VdbeSetVarmask(pParse->pVdbe, iCol); /* IMP: R-23257-02778 */
assert( pRight->op==TK_VARIABLE || pRight->op==TK_REGISTER );
}else if( op==TK_STRING ){
z = pRight->u.zToken;
}
if( z ){
cnt = 0;
while( (c=z[cnt])!=0 && c!=wc[0] && c!=wc[1] && c!=wc[2] ){
cnt++;
}
if( cnt!=0 && 255!=(u8)z[cnt-1] ){
Expr *pPrefix;
*pisComplete = c==wc[0] && z[cnt+1]==0;
pPrefix = sqlite3Expr(db, TK_STRING, z);
if( pPrefix ) pPrefix->u.zToken[cnt] = 0;
*ppPrefix = pPrefix;
if( op==TK_VARIABLE ){
Vdbe *v = pParse->pVdbe;
sqlite3VdbeSetVarmask(v, pRight->iColumn); /* IMP: R-23257-02778 */
if( *pisComplete && pRight->u.zToken[1] ){
/* If the rhs of the LIKE expression is a variable, and the current
** value of the variable means there is no need to invoke the LIKE
** function, then no OP_Variable will be added to the program.
** This causes problems for the sqlite3_bind_parameter_name()
** API. To workaround them, add a dummy OP_Variable here.
*/
int r1 = sqlite3GetTempReg(pParse);
sqlite3ExprCodeTarget(pParse, pRight, r1);
sqlite3VdbeChangeP3(v, sqlite3VdbeCurrentAddr(v)-1, 0);
sqlite3ReleaseTempReg(pParse, r1);
}
}
}else{
z = 0;
}
}
sqlite3ValueFree(pVal);
return (z!=0);
}
#endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */
#ifndef SQLITE_OMIT_VIRTUALTABLE
/*
** Check to see if the given expression is of the form
**
** column MATCH expr
**
** If it is then return TRUE. If not, return FALSE.
*/
static int isMatchOfColumn(
Expr *pExpr /* Test this expression */
){
ExprList *pList;
if( pExpr->op!=TK_FUNCTION ){
return 0;
}
if( sqlite3StrICmp(pExpr->u.zToken,"match")!=0 ){
return 0;
}
pList = pExpr->x.pList;
if( pList->nExpr!=2 ){
return 0;
}
if( pList->a[1].pExpr->op != TK_COLUMN ){
return 0;
}
return 1;
}
#endif /* SQLITE_OMIT_VIRTUALTABLE */
/*
** If the pBase expression originated in the ON or USING clause of
** a join, then transfer the appropriate markings over to derived.
*/
static void transferJoinMarkings(Expr *pDerived, Expr *pBase){
pDerived->flags |= pBase->flags & EP_FromJoin;
pDerived->iRightJoinTable = pBase->iRightJoinTable;
}
#if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY)
/*
** Analyze a term that consists of two or more OR-connected
** subterms. So in:
**
** ... WHERE (a=5) AND (b=7 OR c=9 OR d=13) AND (d=13)
** ^^^^^^^^^^^^^^^^^^^^
**
** This routine analyzes terms such as the middle term in the above example.
** A WhereOrTerm object is computed and attached to the term under
** analysis, regardless of the outcome of the analysis. Hence:
**
** WhereTerm.wtFlags |= TERM_ORINFO
** WhereTerm.u.pOrInfo = a dynamically allocated WhereOrTerm object
**
** The term being analyzed must have two or more of OR-connected subterms.
** A single subterm might be a set of AND-connected sub-subterms.
** Examples of terms under analysis:
**
** (A) t1.x=t2.y OR t1.x=t2.z OR t1.y=15 OR t1.z=t3.a+5
** (B) x=expr1 OR expr2=x OR x=expr3
** (C) t1.x=t2.y OR (t1.x=t2.z AND t1.y=15)
** (D) x=expr1 OR (y>11 AND y<22 AND z LIKE '*hello*')
** (E) (p.a=1 AND q.b=2 AND r.c=3) OR (p.x=4 AND q.y=5 AND r.z=6)
**
** CASE 1:
**
** If all subterms are of the form T.C=expr for some single column of C
** a single table T (as shown in example B above) then create a new virtual
** term that is an equivalent IN expression. In other words, if the term
** being analyzed is:
**
** x = expr1 OR expr2 = x OR x = expr3
**
** then create a new virtual term like this:
**
** x IN (expr1,expr2,expr3)
**
** CASE 2:
**
** If all subterms are indexable by a single table T, then set
**
** WhereTerm.eOperator = WO_OR
** WhereTerm.u.pOrInfo->indexable |= the cursor number for table T
**
** A subterm is "indexable" if it is of the form
** "T.C <op> <expr>" where C is any column of table T and
** <op> is one of "=", "<", "<=", ">", ">=", "IS NULL", or "IN".
** A subterm is also indexable if it is an AND of two or more
** subsubterms at least one of which is indexable. Indexable AND
** subterms have their eOperator set to WO_AND and they have
** u.pAndInfo set to a dynamically allocated WhereAndTerm object.
**
** From another point of view, "indexable" means that the subterm could
** potentially be used with an index if an appropriate index exists.
** This analysis does not consider whether or not the index exists; that
** is something the bestIndex() routine will determine. This analysis
** only looks at whether subterms appropriate for indexing exist.
**
** All examples A through E above all satisfy case 2. But if a term
** also statisfies case 1 (such as B) we know that the optimizer will
** always prefer case 1, so in that case we pretend that case 2 is not
** satisfied.
**
** It might be the case that multiple tables are indexable. For example,
** (E) above is indexable on tables P, Q, and R.
**
** Terms that satisfy case 2 are candidates for lookup by using
** separate indices to find rowids for each subterm and composing
** the union of all rowids using a RowSet object. This is similar
** to "bitmap indices" in other database engines.
**
** OTHERWISE:
**
** If neither case 1 nor case 2 apply, then leave the eOperator set to
** zero. This term is not useful for search.
*/
static void exprAnalyzeOrTerm(
SrcList *pSrc, /* the FROM clause */
WhereClause *pWC, /* the complete WHERE clause */
int idxTerm /* Index of the OR-term to be analyzed */
){
Parse *pParse = pWC->pParse; /* Parser context */
sqlite3 *db = pParse->db; /* Database connection */
WhereTerm *pTerm = &pWC->a[idxTerm]; /* The term to be analyzed */
Expr *pExpr = pTerm->pExpr; /* The expression of the term */
WhereMaskSet *pMaskSet = pWC->pMaskSet; /* Table use masks */
int i; /* Loop counters */
WhereClause *pOrWc; /* Breakup of pTerm into subterms */
WhereTerm *pOrTerm; /* A Sub-term within the pOrWc */
WhereOrInfo *pOrInfo; /* Additional information associated with pTerm */
Bitmask chngToIN; /* Tables that might satisfy case 1 */
Bitmask indexable; /* Tables that are indexable, satisfying case 2 */
/*
** Break the OR clause into its separate subterms. The subterms are
** stored in a WhereClause structure containing within the WhereOrInfo
** object that is attached to the original OR clause term.
*/
assert( (pTerm->wtFlags & (TERM_DYNAMIC|TERM_ORINFO|TERM_ANDINFO))==0 );
assert( pExpr->op==TK_OR );
pTerm->u.pOrInfo = pOrInfo = sqlite3DbMallocZero(db, sizeof(*pOrInfo));
if( pOrInfo==0 ) return;
pTerm->wtFlags |= TERM_ORINFO;
pOrWc = &pOrInfo->wc;
whereClauseInit(pOrWc, pWC->pParse, pMaskSet);
whereSplit(pOrWc, pExpr, TK_OR);
exprAnalyzeAll(pSrc, pOrWc);
if( db->mallocFailed ) return;
assert( pOrWc->nTerm>=2 );
/*
** Compute the set of tables that might satisfy cases 1 or 2.
*/
indexable = ~(Bitmask)0;
chngToIN = ~(pWC->vmask);
for(i=pOrWc->nTerm-1, pOrTerm=pOrWc->a; i>=0 && indexable; i--, pOrTerm++){
if( (pOrTerm->eOperator & WO_SINGLE)==0 ){
WhereAndInfo *pAndInfo;
assert( pOrTerm->eOperator==0 );
assert( (pOrTerm->wtFlags & (TERM_ANDINFO|TERM_ORINFO))==0 );
chngToIN = 0;
pAndInfo = sqlite3DbMallocRaw(db, sizeof(*pAndInfo));
if( pAndInfo ){
WhereClause *pAndWC;
WhereTerm *pAndTerm;
int j;
Bitmask b = 0;
pOrTerm->u.pAndInfo = pAndInfo;
pOrTerm->wtFlags |= TERM_ANDINFO;
pOrTerm->eOperator = WO_AND;
pAndWC = &pAndInfo->wc;
whereClauseInit(pAndWC, pWC->pParse, pMaskSet);
whereSplit(pAndWC, pOrTerm->pExpr, TK_AND);
exprAnalyzeAll(pSrc, pAndWC);
testcase( db->mallocFailed );
if( !db->mallocFailed ){
for(j=0, pAndTerm=pAndWC->a; j<pAndWC->nTerm; j++, pAndTerm++){
assert( pAndTerm->pExpr );
if( allowedOp(pAndTerm->pExpr->op) ){
b |= getMask(pMaskSet, pAndTerm->leftCursor);
}
}
}
indexable &= b;
}
}else if( pOrTerm->wtFlags & TERM_COPIED ){
/* Skip this term for now. We revisit it when we process the
** corresponding TERM_VIRTUAL term */
}else{
Bitmask b;
b = getMask(pMaskSet, pOrTerm->leftCursor);
if( pOrTerm->wtFlags & TERM_VIRTUAL ){
WhereTerm *pOther = &pOrWc->a[pOrTerm->iParent];
b |= getMask(pMaskSet, pOther->leftCursor);
}
indexable &= b;
if( pOrTerm->eOperator!=WO_EQ ){
chngToIN = 0;
}else{
chngToIN &= b;
}
}
}
/*
** Record the set of tables that satisfy case 2. The set might be
** empty.
*/
pOrInfo->indexable = indexable;
pTerm->eOperator = indexable==0 ? 0 : WO_OR;
/*
** chngToIN holds a set of tables that *might* satisfy case 1. But
** we have to do some additional checking to see if case 1 really
** is satisfied.
**
** chngToIN will hold either 0, 1, or 2 bits. The 0-bit case means
** that there is no possibility of transforming the OR clause into an
** IN operator because one or more terms in the OR clause contain
** something other than == on a column in the single table. The 1-bit
** case means that every term of the OR clause is of the form
** "table.column=expr" for some single table. The one bit that is set
** will correspond to the common table. We still need to check to make
** sure the same column is used on all terms. The 2-bit case is when
** the all terms are of the form "table1.column=table2.column". It
** might be possible to form an IN operator with either table1.column
** or table2.column as the LHS if either is common to every term of
** the OR clause.
**
** Note that terms of the form "table.column1=table.column2" (the
** same table on both sizes of the ==) cannot be optimized.
*/
if( chngToIN ){
int okToChngToIN = 0; /* True if the conversion to IN is valid */
int iColumn = -1; /* Column index on lhs of IN operator */
int iCursor = -1; /* Table cursor common to all terms */
int j = 0; /* Loop counter */
/* Search for a table and column that appears on one side or the
** other of the == operator in every subterm. That table and column
** will be recorded in iCursor and iColumn. There might not be any
** such table and column. Set okToChngToIN if an appropriate table
** and column is found but leave okToChngToIN false if not found.
*/
for(j=0; j<2 && !okToChngToIN; j++){
pOrTerm = pOrWc->a;
for(i=pOrWc->nTerm-1; i>=0; i--, pOrTerm++){
assert( pOrTerm->eOperator==WO_EQ );
pOrTerm->wtFlags &= ~TERM_OR_OK;
if( pOrTerm->leftCursor==iCursor ){
/* This is the 2-bit case and we are on the second iteration and
** current term is from the first iteration. So skip this term. */
assert( j==1 );
continue;
}
if( (chngToIN & getMask(pMaskSet, pOrTerm->leftCursor))==0 ){
/* This term must be of the form t1.a==t2.b where t2 is in the
** chngToIN set but t1 is not. This term will be either preceeded
** or follwed by an inverted copy (t2.b==t1.a). Skip this term
** and use its inversion. */
testcase( pOrTerm->wtFlags & TERM_COPIED );
testcase( pOrTerm->wtFlags & TERM_VIRTUAL );
assert( pOrTerm->wtFlags & (TERM_COPIED|TERM_VIRTUAL) );
continue;
}
iColumn = pOrTerm->u.leftColumn;
iCursor = pOrTerm->leftCursor;
break;
}
if( i<0 ){
/* No candidate table+column was found. This can only occur
** on the second iteration */
assert( j==1 );
assert( (chngToIN&(chngToIN-1))==0 );
assert( chngToIN==getMask(pMaskSet, iCursor) );
break;
}
testcase( j==1 );
/* We have found a candidate table and column. Check to see if that
** table and column is common to every term in the OR clause */
okToChngToIN = 1;
for(; i>=0 && okToChngToIN; i--, pOrTerm++){
assert( pOrTerm->eOperator==WO_EQ );
if( pOrTerm->leftCursor!=iCursor ){
pOrTerm->wtFlags &= ~TERM_OR_OK;
}else if( pOrTerm->u.leftColumn!=iColumn ){
okToChngToIN = 0;
}else{
int affLeft, affRight;
/* If the right-hand side is also a column, then the affinities
** of both right and left sides must be such that no type
** conversions are required on the right. (Ticket #2249)
*/
affRight = sqlite3ExprAffinity(pOrTerm->pExpr->pRight);
affLeft = sqlite3ExprAffinity(pOrTerm->pExpr->pLeft);
if( affRight!=0 && affRight!=affLeft ){
okToChngToIN = 0;
}else{
pOrTerm->wtFlags |= TERM_OR_OK;
}
}
}
}
/* At this point, okToChngToIN is true if original pTerm satisfies
** case 1. In that case, construct a new virtual term that is
** pTerm converted into an IN operator.
**
** EV: R-00211-15100
*/
if( okToChngToIN ){
Expr *pDup; /* A transient duplicate expression */
ExprList *pList = 0; /* The RHS of the IN operator */
Expr *pLeft = 0; /* The LHS of the IN operator */
Expr *pNew; /* The complete IN operator */
for(i=pOrWc->nTerm-1, pOrTerm=pOrWc->a; i>=0; i--, pOrTerm++){
if( (pOrTerm->wtFlags & TERM_OR_OK)==0 ) continue;
assert( pOrTerm->eOperator==WO_EQ );
assert( pOrTerm->leftCursor==iCursor );
assert( pOrTerm->u.leftColumn==iColumn );
pDup = sqlite3ExprDup(db, pOrTerm->pExpr->pRight, 0);
pList = sqlite3ExprListAppend(pWC->pParse, pList, pDup);
pLeft = pOrTerm->pExpr->pLeft;
}
assert( pLeft!=0 );
pDup = sqlite3ExprDup(db, pLeft, 0);
pNew = sqlite3PExpr(pParse, TK_IN, pDup, 0, 0);
if( pNew ){
int idxNew;
transferJoinMarkings(pNew, pExpr);
assert( !ExprHasProperty(pNew, EP_xIsSelect) );
pNew->x.pList = pList;
idxNew = whereClauseInsert(pWC, pNew, TERM_VIRTUAL|TERM_DYNAMIC);
testcase( idxNew==0 );
exprAnalyze(pSrc, pWC, idxNew);
pTerm = &pWC->a[idxTerm];
pWC->a[idxNew].iParent = idxTerm;
pTerm->nChild = 1;
}else{
sqlite3ExprListDelete(db, pList);
}
pTerm->eOperator = WO_NOOP; /* case 1 trumps case 2 */
}
}
}
#endif /* !SQLITE_OMIT_OR_OPTIMIZATION && !SQLITE_OMIT_SUBQUERY */
/*
** The input to this routine is an WhereTerm structure with only the
** "pExpr" field filled in. The job of this routine is to analyze the
** subexpression and populate all the other fields of the WhereTerm
** structure.
**
** If the expression is of the form "<expr> <op> X" it gets commuted
** to the standard form of "X <op> <expr>".
**
** If the expression is of the form "X <op> Y" where both X and Y are
** columns, then the original expression is unchanged and a new virtual
** term of the form "Y <op> X" is added to the WHERE clause and
** analyzed separately. The original term is marked with TERM_COPIED
** and the new term is marked with TERM_DYNAMIC (because it's pExpr
** needs to be freed with the WhereClause) and TERM_VIRTUAL (because it
** is a commuted copy of a prior term.) The original term has nChild=1
** and the copy has idxParent set to the index of the original term.
*/
static void exprAnalyze(
SrcList *pSrc, /* the FROM clause */
WhereClause *pWC, /* the WHERE clause */
int idxTerm /* Index of the term to be analyzed */
){
WhereTerm *pTerm; /* The term to be analyzed */
WhereMaskSet *pMaskSet; /* Set of table index masks */
Expr *pExpr; /* The expression to be analyzed */
Bitmask prereqLeft; /* Prerequesites of the pExpr->pLeft */
Bitmask prereqAll; /* Prerequesites of pExpr */
Bitmask extraRight = 0; /* Extra dependencies on LEFT JOIN */
Expr *pStr1 = 0; /* RHS of LIKE/GLOB operator */
int isComplete = 0; /* RHS of LIKE/GLOB ends with wildcard */
int noCase = 0; /* LIKE/GLOB distinguishes case */
int op; /* Top-level operator. pExpr->op */
Parse *pParse = pWC->pParse; /* Parsing context */
sqlite3 *db = pParse->db; /* Database connection */
if( db->mallocFailed ){
return;
}
pTerm = &pWC->a[idxTerm];
pMaskSet = pWC->pMaskSet;
pExpr = pTerm->pExpr;
prereqLeft = exprTableUsage(pMaskSet, pExpr->pLeft);
op = pExpr->op;
if( op==TK_IN ){
assert( pExpr->pRight==0 );
if( ExprHasProperty(pExpr, EP_xIsSelect) ){
pTerm->prereqRight = exprSelectTableUsage(pMaskSet, pExpr->x.pSelect);
}else{
pTerm->prereqRight = exprListTableUsage(pMaskSet, pExpr->x.pList);
}
}else if( op==TK_ISNULL ){
pTerm->prereqRight = 0;
}else{
pTerm->prereqRight = exprTableUsage(pMaskSet, pExpr->pRight);
}
prereqAll = exprTableUsage(pMaskSet, pExpr);
if( ExprHasProperty(pExpr, EP_FromJoin) ){
Bitmask x = getMask(pMaskSet, pExpr->iRightJoinTable);
prereqAll |= x;
extraRight = x-1; /* ON clause terms may not be used with an index
** on left table of a LEFT JOIN. Ticket #3015 */
}
pTerm->prereqAll = prereqAll;
pTerm->leftCursor = -1;
pTerm->iParent = -1;
pTerm->eOperator = 0;
if( allowedOp(op) && (pTerm->prereqRight & prereqLeft)==0 ){
Expr *pLeft = pExpr->pLeft;
Expr *pRight = pExpr->pRight;
if( pLeft->op==TK_COLUMN ){
pTerm->leftCursor = pLeft->iTable;
pTerm->u.leftColumn = pLeft->iColumn;
pTerm->eOperator = operatorMask(op);
}
if( pRight && pRight->op==TK_COLUMN ){
WhereTerm *pNew;
Expr *pDup;
if( pTerm->leftCursor>=0 ){
int idxNew;
pDup = sqlite3ExprDup(db, pExpr, 0);
if( db->mallocFailed ){
sqlite3ExprDelete(db, pDup);
return;
}
idxNew = whereClauseInsert(pWC, pDup, TERM_VIRTUAL|TERM_DYNAMIC);
if( idxNew==0 ) return;
pNew = &pWC->a[idxNew];
pNew->iParent = idxTerm;
pTerm = &pWC->a[idxTerm];
pTerm->nChild = 1;
pTerm->wtFlags |= TERM_COPIED;
}else{
pDup = pExpr;
pNew = pTerm;
}
exprCommute(pParse, pDup);
pLeft = pDup->pLeft;
pNew->leftCursor = pLeft->iTable;
pNew->u.leftColumn = pLeft->iColumn;
testcase( (prereqLeft | extraRight) != prereqLeft );
pNew->prereqRight = prereqLeft | extraRight;
pNew->prereqAll = prereqAll;
pNew->eOperator = operatorMask(pDup->op);
}
}
#ifndef SQLITE_OMIT_BETWEEN_OPTIMIZATION
/* If a term is the BETWEEN operator, create two new virtual terms
** that define the range that the BETWEEN implements. For example:
**
** a BETWEEN b AND c
**
** is converted into:
**
** (a BETWEEN b AND c) AND (a>=b) AND (a<=c)
**
** The two new terms are added onto the end of the WhereClause object.
** The new terms are "dynamic" and are children of the original BETWEEN
** term. That means that if the BETWEEN term is coded, the children are
** skipped. Or, if the children are satisfied by an index, the original
** BETWEEN term is skipped.
*/
else if( pExpr->op==TK_BETWEEN && pWC->op==TK_AND ){
ExprList *pList = pExpr->x.pList;
int i;
static const u8 ops[] = {TK_GE, TK_LE};
assert( pList!=0 );
assert( pList->nExpr==2 );
for(i=0; i<2; i++){
Expr *pNewExpr;
int idxNew;
pNewExpr = sqlite3PExpr(pParse, ops[i],
sqlite3ExprDup(db, pExpr->pLeft, 0),
sqlite3ExprDup(db, pList->a[i].pExpr, 0), 0);
idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC);
testcase( idxNew==0 );
exprAnalyze(pSrc, pWC, idxNew);
pTerm = &pWC->a[idxTerm];
pWC->a[idxNew].iParent = idxTerm;
}
pTerm->nChild = 2;
}
#endif /* SQLITE_OMIT_BETWEEN_OPTIMIZATION */
#if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY)
/* Analyze a term that is composed of two or more subterms connected by
** an OR operator.
*/
else if( pExpr->op==TK_OR ){
assert( pWC->op==TK_AND );
exprAnalyzeOrTerm(pSrc, pWC, idxTerm);
pTerm = &pWC->a[idxTerm];
}
#endif /* SQLITE_OMIT_OR_OPTIMIZATION */
#ifndef SQLITE_OMIT_LIKE_OPTIMIZATION
/* Add constraints to reduce the search space on a LIKE or GLOB
** operator.
**
** A like pattern of the form "x LIKE 'abc%'" is changed into constraints
**
** x>='abc' AND x<'abd' AND x LIKE 'abc%'
**
** The last character of the prefix "abc" is incremented to form the
** termination condition "abd".
*/
if( pWC->op==TK_AND
&& isLikeOrGlob(pParse, pExpr, &pStr1, &isComplete, &noCase)
){
Expr *pLeft; /* LHS of LIKE/GLOB operator */
Expr *pStr2; /* Copy of pStr1 - RHS of LIKE/GLOB operator */
Expr *pNewExpr1;
Expr *pNewExpr2;
int idxNew1;
int idxNew2;
CollSeq *pColl; /* Collating sequence to use */
pLeft = pExpr->x.pList->a[1].pExpr;
pStr2 = sqlite3ExprDup(db, pStr1, 0);
if( !db->mallocFailed ){
u8 c, *pC; /* Last character before the first wildcard */
pC = (u8*)&pStr2->u.zToken[sqlite3Strlen30(pStr2->u.zToken)-1];
c = *pC;
if( noCase ){
/* The point is to increment the last character before the first
** wildcard. But if we increment '@', that will push it into the
** alphabetic range where case conversions will mess up the
** inequality. To avoid this, make sure to also run the full
** LIKE on all candidate expressions by clearing the isComplete flag
*/
if( c=='A'-1 ) isComplete = 0; /* EV: R-64339-08207 */
c = sqlite3UpperToLower[c];
}
*pC = c + 1;
}
pColl = sqlite3FindCollSeq(db, SQLITE_UTF8, noCase ? "NOCASE" : "BINARY",0);
pNewExpr1 = sqlite3PExpr(pParse, TK_GE,
sqlite3ExprSetColl(sqlite3ExprDup(db,pLeft,0), pColl),
pStr1, 0);
idxNew1 = whereClauseInsert(pWC, pNewExpr1, TERM_VIRTUAL|TERM_DYNAMIC);
testcase( idxNew1==0 );
exprAnalyze(pSrc, pWC, idxNew1);
pNewExpr2 = sqlite3PExpr(pParse, TK_LT,
sqlite3ExprSetColl(sqlite3ExprDup(db,pLeft,0), pColl),
pStr2, 0);
idxNew2 = whereClauseInsert(pWC, pNewExpr2, TERM_VIRTUAL|TERM_DYNAMIC);
testcase( idxNew2==0 );
exprAnalyze(pSrc, pWC, idxNew2);
pTerm = &pWC->a[idxTerm];
if( isComplete ){
pWC->a[idxNew1].iParent = idxTerm;
pWC->a[idxNew2].iParent = idxTerm;
pTerm->nChild = 2;
}
}
#endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */
#ifndef SQLITE_OMIT_VIRTUALTABLE
/* Add a WO_MATCH auxiliary term to the constraint set if the
** current expression is of the form: column MATCH expr.
** This information is used by the xBestIndex methods of
** virtual tables. The native query optimizer does not attempt
** to do anything with MATCH functions.
*/
if( isMatchOfColumn(pExpr) ){
int idxNew;
Expr *pRight, *pLeft;
WhereTerm *pNewTerm;
Bitmask prereqColumn, prereqExpr;
pRight = pExpr->x.pList->a[0].pExpr;
pLeft = pExpr->x.pList->a[1].pExpr;
prereqExpr = exprTableUsage(pMaskSet, pRight);
prereqColumn = exprTableUsage(pMaskSet, pLeft);
if( (prereqExpr & prereqColumn)==0 ){
Expr *pNewExpr;
pNewExpr = sqlite3PExpr(pParse, TK_MATCH,
0, sqlite3ExprDup(db, pRight, 0), 0);
idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC);
testcase( idxNew==0 );
pNewTerm = &pWC->a[idxNew];
pNewTerm->prereqRight = prereqExpr;
pNewTerm->leftCursor = pLeft->iTable;
pNewTerm->u.leftColumn = pLeft->iColumn;
pNewTerm->eOperator = WO_MATCH;
pNewTerm->iParent = idxTerm;
pTerm = &pWC->a[idxTerm];
pTerm->nChild = 1;
pTerm->wtFlags |= TERM_COPIED;
pNewTerm->prereqAll = pTerm->prereqAll;
}
}
#endif /* SQLITE_OMIT_VIRTUALTABLE */
#ifdef SQLITE_ENABLE_STAT2
/* When sqlite_stat2 histogram data is available an operator of the
** form "x IS NOT NULL" can sometimes be evaluated more efficiently
** as "x>NULL" if x is not an INTEGER PRIMARY KEY. So construct a
** virtual term of that form.
**
** Note that the virtual term must be tagged with TERM_VNULL. This
** TERM_VNULL tag will suppress the not-null check at the beginning
** of the loop. Without the TERM_VNULL flag, the not-null check at
** the start of the loop will prevent any results from being returned.
*/
if( pExpr->op==TK_NOTNULL
&& pExpr->pLeft->op==TK_COLUMN
&& pExpr->pLeft->iColumn>=0
){
Expr *pNewExpr;
Expr *pLeft = pExpr->pLeft;
int idxNew;
WhereTerm *pNewTerm;
pNewExpr = sqlite3PExpr(pParse, TK_GT,
sqlite3ExprDup(db, pLeft, 0),
sqlite3PExpr(pParse, TK_NULL, 0, 0, 0), 0);
idxNew = whereClauseInsert(pWC, pNewExpr,
TERM_VIRTUAL|TERM_DYNAMIC|TERM_VNULL);
if( idxNew ){
pNewTerm = &pWC->a[idxNew];
pNewTerm->prereqRight = 0;
pNewTerm->leftCursor = pLeft->iTable;
pNewTerm->u.leftColumn = pLeft->iColumn;
pNewTerm->eOperator = WO_GT;
pNewTerm->iParent = idxTerm;
pTerm = &pWC->a[idxTerm];
pTerm->nChild = 1;
pTerm->wtFlags |= TERM_COPIED;
pNewTerm->prereqAll = pTerm->prereqAll;
}
}
#endif /* SQLITE_ENABLE_STAT2 */
/* Prevent ON clause terms of a LEFT JOIN from being used to drive
** an index for tables to the left of the join.
*/
pTerm->prereqRight |= extraRight;
}
/*
** Return TRUE if any of the expressions in pList->a[iFirst...] contain
** a reference to any table other than the iBase table.
*/
static int referencesOtherTables(
ExprList *pList, /* Search expressions in ths list */
WhereMaskSet *pMaskSet, /* Mapping from tables to bitmaps */
int iFirst, /* Be searching with the iFirst-th expression */
int iBase /* Ignore references to this table */
){
Bitmask allowed = ~getMask(pMaskSet, iBase);
while( iFirst<pList->nExpr ){
if( (exprTableUsage(pMaskSet, pList->a[iFirst++].pExpr)&allowed)!=0 ){
return 1;
}
}
return 0;
}
/*
** This routine decides if pIdx can be used to satisfy the ORDER BY
** clause. If it can, it returns 1. If pIdx cannot satisfy the
** ORDER BY clause, this routine returns 0.
**
** pOrderBy is an ORDER BY clause from a SELECT statement. pTab is the
** left-most table in the FROM clause of that same SELECT statement and
** the table has a cursor number of "base". pIdx is an index on pTab.
**
** nEqCol is the number of columns of pIdx that are used as equality
** constraints. Any of these columns may be missing from the ORDER BY
** clause and the match can still be a success.
**
** All terms of the ORDER BY that match against the index must be either
** ASC or DESC. (Terms of the ORDER BY clause past the end of a UNIQUE
** index do not need to satisfy this constraint.) The *pbRev value is
** set to 1 if the ORDER BY clause is all DESC and it is set to 0 if
** the ORDER BY clause is all ASC.
*/
static int isSortingIndex(
Parse *pParse, /* Parsing context */
WhereMaskSet *pMaskSet, /* Mapping from table cursor numbers to bitmaps */
Index *pIdx, /* The index we are testing */
int base, /* Cursor number for the table to be sorted */
ExprList *pOrderBy, /* The ORDER BY clause */
int nEqCol, /* Number of index columns with == constraints */
int wsFlags, /* Index usages flags */
int *pbRev /* Set to 1 if ORDER BY is DESC */
){
int i, j; /* Loop counters */
int sortOrder = 0; /* XOR of index and ORDER BY sort direction */
int nTerm; /* Number of ORDER BY terms */
struct ExprList_item *pTerm; /* A term of the ORDER BY clause */
sqlite3 *db = pParse->db;
assert( pOrderBy!=0 );
nTerm = pOrderBy->nExpr;
assert( nTerm>0 );
/* Argument pIdx must either point to a 'real' named index structure,
** or an index structure allocated on the stack by bestBtreeIndex() to
** represent the rowid index that is part of every table. */
assert( pIdx->zName || (pIdx->nColumn==1 && pIdx->aiColumn[0]==-1) );
/* Match terms of the ORDER BY clause against columns of
** the index.
**
** Note that indices have pIdx->nColumn regular columns plus
** one additional column containing the rowid. The rowid column
** of the index is also allowed to match against the ORDER BY
** clause.
*/
for(i=j=0, pTerm=pOrderBy->a; j<nTerm && i<=pIdx->nColumn; i++){
Expr *pExpr; /* The expression of the ORDER BY pTerm */
CollSeq *pColl; /* The collating sequence of pExpr */
int termSortOrder; /* Sort order for this term */
int iColumn; /* The i-th column of the index. -1 for rowid */
int iSortOrder; /* 1 for DESC, 0 for ASC on the i-th index term */
const char *zColl; /* Name of the collating sequence for i-th index term */
pExpr = pTerm->pExpr;
if( pExpr->op!=TK_COLUMN || pExpr->iTable!=base ){
/* Can not use an index sort on anything that is not a column in the
** left-most table of the FROM clause */
break;
}
pColl = sqlite3ExprCollSeq(pParse, pExpr);
if( !pColl ){
pColl = db->pDfltColl;
}
if( pIdx->zName && i<pIdx->nColumn ){
iColumn = pIdx->aiColumn[i];
if( iColumn==pIdx->pTable->iPKey ){
iColumn = -1;
}
iSortOrder = pIdx->aSortOrder[i];
zColl = pIdx->azColl[i];
}else{
iColumn = -1;
iSortOrder = 0;
zColl = pColl->zName;
}
if( pExpr->iColumn!=iColumn || sqlite3StrICmp(pColl->zName, zColl) ){
/* Term j of the ORDER BY clause does not match column i of the index */
if( i<nEqCol ){
/* If an index column that is constrained by == fails to match an
** ORDER BY term, that is OK. Just ignore that column of the index
*/
continue;
}else if( i==pIdx->nColumn ){
/* Index column i is the rowid. All other terms match. */
break;
}else{
/* If an index column fails to match and is not constrained by ==
** then the index cannot satisfy the ORDER BY constraint.
*/
return 0;
}
}
assert( pIdx->aSortOrder!=0 || iColumn==-1 );
assert( pTerm->sortOrder==0 || pTerm->sortOrder==1 );
assert( iSortOrder==0 || iSortOrder==1 );
termSortOrder = iSortOrder ^ pTerm->sortOrder;
if( i>nEqCol ){
if( termSortOrder!=sortOrder ){
/* Indices can only be used if all ORDER BY terms past the
** equality constraints are all either DESC or ASC. */
return 0;
}
}else{
sortOrder = termSortOrder;
}
j++;
pTerm++;
if( iColumn<0 && !referencesOtherTables(pOrderBy, pMaskSet, j, base) ){
/* If the indexed column is the primary key and everything matches
** so far and none of the ORDER BY terms to the right reference other
** tables in the join, then we are assured that the index can be used
** to sort because the primary key is unique and so none of the other
** columns will make any difference
*/
j = nTerm;
}
}
*pbRev = sortOrder!=0;
if( j>=nTerm ){
/* All terms of the ORDER BY clause are covered by this index so
** this index can be used for sorting. */
return 1;
}
if( pIdx->onError!=OE_None && i==pIdx->nColumn
&& (wsFlags & WHERE_COLUMN_NULL)==0
&& !referencesOtherTables(pOrderBy, pMaskSet, j, base) ){
/* All terms of this index match some prefix of the ORDER BY clause
** and the index is UNIQUE and no terms on the tail of the ORDER BY
** clause reference other tables in a join. If this is all true then
** the order by clause is superfluous. Not that if the matching
** condition is IS NULL then the result is not necessarily unique
** even on a UNIQUE index, so disallow those cases. */
return 1;
}
return 0;
}
/*
** Prepare a crude estimate of the logarithm of the input value.
** The results need not be exact. This is only used for estimating
** the total cost of performing operations with O(logN) or O(NlogN)
** complexity. Because N is just a guess, it is no great tragedy if
** logN is a little off.
*/
static double estLog(double N){
double logN = 1;
double x = 10;
while( N>x ){
logN += 1;
x *= 10;
}
return logN;
}
/*
** Two routines for printing the content of an sqlite3_index_info
** structure. Used for testing and debugging only. If neither
** SQLITE_TEST or SQLITE_DEBUG are defined, then these routines
** are no-ops.
*/
#if !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(SQLITE_DEBUG)
static void TRACE_IDX_INPUTS(sqlite3_index_info *p){
int i;
if( !sqlite3WhereTrace ) return;
for(i=0; i<p->nConstraint; i++){
sqlite3DebugPrintf(" constraint[%d]: col=%d termid=%d op=%d usabled=%d\n",
i,
p->aConstraint[i].iColumn,
p->aConstraint[i].iTermOffset,
p->aConstraint[i].op,
p->aConstraint[i].usable);
}
for(i=0; i<p->nOrderBy; i++){
sqlite3DebugPrintf(" orderby[%d]: col=%d desc=%d\n",
i,
p->aOrderBy[i].iColumn,
p->aOrderBy[i].desc);
}
}
static void TRACE_IDX_OUTPUTS(sqlite3_index_info *p){
int i;
if( !sqlite3WhereTrace ) return;
for(i=0; i<p->nConstraint; i++){
sqlite3DebugPrintf(" usage[%d]: argvIdx=%d omit=%d\n",
i,
p->aConstraintUsage[i].argvIndex,
p->aConstraintUsage[i].omit);
}
sqlite3DebugPrintf(" idxNum=%d\n", p->idxNum);
sqlite3DebugPrintf(" idxStr=%s\n", p->idxStr);
sqlite3DebugPrintf(" orderByConsumed=%d\n", p->orderByConsumed);
sqlite3DebugPrintf(" estimatedCost=%g\n", p->estimatedCost);
}
#else
#define TRACE_IDX_INPUTS(A)
#define TRACE_IDX_OUTPUTS(A)
#endif
/*
** Required because bestIndex() is called by bestOrClauseIndex()
*/
static void bestIndex(
Parse*, WhereClause*, struct SrcList_item*,
Bitmask, Bitmask, ExprList*, WhereCost*);
/*
** This routine attempts to find an scanning strategy that can be used
** to optimize an 'OR' expression that is part of a WHERE clause.
**
** The table associated with FROM clause term pSrc may be either a
** regular B-Tree table or a virtual table.
*/
static void bestOrClauseIndex(
Parse *pParse, /* The parsing context */
WhereClause *pWC, /* The WHERE clause */
struct SrcList_item *pSrc, /* The FROM clause term to search */
Bitmask notReady, /* Mask of cursors not available for indexing */
Bitmask notValid, /* Cursors not available for any purpose */
ExprList *pOrderBy, /* The ORDER BY clause */
WhereCost *pCost /* Lowest cost query plan */
){
#ifndef SQLITE_OMIT_OR_OPTIMIZATION
const int iCur = pSrc->iCursor; /* The cursor of the table to be accessed */
const Bitmask maskSrc = getMask(pWC->pMaskSet, iCur); /* Bitmask for pSrc */
WhereTerm * const pWCEnd = &pWC->a[pWC->nTerm]; /* End of pWC->a[] */
WhereTerm *pTerm; /* A single term of the WHERE clause */
/* No OR-clause optimization allowed if the INDEXED BY or NOT INDEXED clauses
** are used */
if( pSrc->notIndexed || pSrc->pIndex!=0 ){
return;
}
/* Search the WHERE clause terms for a usable WO_OR term. */
for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
if( pTerm->eOperator==WO_OR
&& ((pTerm->prereqAll & ~maskSrc) & notReady)==0
&& (pTerm->u.pOrInfo->indexable & maskSrc)!=0
){
WhereClause * const pOrWC = &pTerm->u.pOrInfo->wc;
WhereTerm * const pOrWCEnd = &pOrWC->a[pOrWC->nTerm];
WhereTerm *pOrTerm;
int flags = WHERE_MULTI_OR;
double rTotal = 0;
double nRow = 0;
Bitmask used = 0;
for(pOrTerm=pOrWC->a; pOrTerm<pOrWCEnd; pOrTerm++){
WhereCost sTermCost;
WHERETRACE(("... Multi-index OR testing for term %d of %d....\n",
(pOrTerm - pOrWC->a), (pTerm - pWC->a)
));
if( pOrTerm->eOperator==WO_AND ){
WhereClause *pAndWC = &pOrTerm->u.pAndInfo->wc;
bestIndex(pParse, pAndWC, pSrc, notReady, notValid, 0, &sTermCost);
}else if( pOrTerm->leftCursor==iCur ){
WhereClause tempWC;
tempWC.pParse = pWC->pParse;
tempWC.pMaskSet = pWC->pMaskSet;
tempWC.op = TK_AND;
tempWC.a = pOrTerm;
tempWC.nTerm = 1;
bestIndex(pParse, &tempWC, pSrc, notReady, notValid, 0, &sTermCost);
}else{
continue;
}
rTotal += sTermCost.rCost;
nRow += sTermCost.plan.nRow;
used |= sTermCost.used;
if( rTotal>=pCost->rCost ) break;
}
/* If there is an ORDER BY clause, increase the scan cost to account
** for the cost of the sort. */
if( pOrderBy!=0 ){
WHERETRACE(("... sorting increases OR cost %.9g to %.9g\n",
rTotal, rTotal+nRow*estLog(nRow)));
rTotal += nRow*estLog(nRow);
}
/* If the cost of scanning using this OR term for optimization is
** less than the current cost stored in pCost, replace the contents
** of pCost. */
WHERETRACE(("... multi-index OR cost=%.9g nrow=%.9g\n", rTotal, nRow));
if( rTotal<pCost->rCost ){
pCost->rCost = rTotal;
pCost->used = used;
pCost->plan.nRow = nRow;
pCost->plan.wsFlags = flags;
pCost->plan.u.pTerm = pTerm;
}
}
}
#endif /* SQLITE_OMIT_OR_OPTIMIZATION */
}
#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
/*
** Return TRUE if the WHERE clause term pTerm is of a form where it
** could be used with an index to access pSrc, assuming an appropriate
** index existed.
*/
static int termCanDriveIndex(
WhereTerm *pTerm, /* WHERE clause term to check */
struct SrcList_item *pSrc, /* Table we are trying to access */
Bitmask notReady /* Tables in outer loops of the join */
){
char aff;
if( pTerm->leftCursor!=pSrc->iCursor ) return 0;
if( pTerm->eOperator!=WO_EQ ) return 0;
if( (pTerm->prereqRight & notReady)!=0 ) return 0;
aff = pSrc->pTab->aCol[pTerm->u.leftColumn].affinity;
if( !sqlite3IndexAffinityOk(pTerm->pExpr, aff) ) return 0;
return 1;
}
#endif
#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
/*
** If the query plan for pSrc specified in pCost is a full table scan
** and indexing is allows (if there is no NOT INDEXED clause) and it
** possible to construct a transient index that would perform better
** than a full table scan even when the cost of constructing the index
** is taken into account, then alter the query plan to use the
** transient index.
*/
static void bestAutomaticIndex(
Parse *pParse, /* The parsing context */
WhereClause *pWC, /* The WHERE clause */
struct SrcList_item *pSrc, /* The FROM clause term to search */
Bitmask notReady, /* Mask of cursors that are not available */
WhereCost *pCost /* Lowest cost query plan */
){
double nTableRow; /* Rows in the input table */
double logN; /* log(nTableRow) */
double costTempIdx; /* per-query cost of the transient index */
WhereTerm *pTerm; /* A single term of the WHERE clause */
WhereTerm *pWCEnd; /* End of pWC->a[] */
Table *pTable; /* Table tht might be indexed */
if( (pParse->db->flags & SQLITE_AutoIndex)==0 ){
/* Automatic indices are disabled at run-time */
return;
}
if( (pCost->plan.wsFlags & WHERE_NOT_FULLSCAN)!=0 ){
/* We already have some kind of index in use for this query. */
return;
}
if( pSrc->notIndexed ){
/* The NOT INDEXED clause appears in the SQL. */
return;
}
assert( pParse->nQueryLoop >= (double)1 );
pTable = pSrc->pTab;
nTableRow = pTable->nRowEst;
logN = estLog(nTableRow);
costTempIdx = 2*logN*(nTableRow/pParse->nQueryLoop + 1);
if( costTempIdx>=pCost->rCost ){
/* The cost of creating the transient table would be greater than
** doing the full table scan */
return;
}
/* Search for any equality comparison term */
pWCEnd = &pWC->a[pWC->nTerm];
for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
if( termCanDriveIndex(pTerm, pSrc, notReady) ){
WHERETRACE(("auto-index reduces cost from %.1f to %.1f\n",
pCost->rCost, costTempIdx));
pCost->rCost = costTempIdx;
pCost->plan.nRow = logN + 1;
pCost->plan.wsFlags = WHERE_TEMP_INDEX;
pCost->used = pTerm->prereqRight;
break;
}
}
}
#else
# define bestAutomaticIndex(A,B,C,D,E) /* no-op */
#endif /* SQLITE_OMIT_AUTOMATIC_INDEX */
#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
/*
** Generate code to construct the Index object for an automatic index
** and to set up the WhereLevel object pLevel so that the code generator
** makes use of the automatic index.
*/
static void constructAutomaticIndex(
Parse *pParse, /* The parsing context */
WhereClause *pWC, /* The WHERE clause */
struct SrcList_item *pSrc, /* The FROM clause term to get the next index */
Bitmask notReady, /* Mask of cursors that are not available */
WhereLevel *pLevel /* Write new index here */
){
int nColumn; /* Number of columns in the constructed index */
WhereTerm *pTerm; /* A single term of the WHERE clause */
WhereTerm *pWCEnd; /* End of pWC->a[] */
int nByte; /* Byte of memory needed for pIdx */
Index *pIdx; /* Object describing the transient index */
Vdbe *v; /* Prepared statement under construction */
int regIsInit; /* Register set by initialization */
int addrInit; /* Address of the initialization bypass jump */
Table *pTable; /* The table being indexed */
KeyInfo *pKeyinfo; /* Key information for the index */
int addrTop; /* Top of the index fill loop */
int regRecord; /* Register holding an index record */
int n; /* Column counter */
int i; /* Loop counter */
int mxBitCol; /* Maximum column in pSrc->colUsed */
CollSeq *pColl; /* Collating sequence to on a column */
Bitmask idxCols; /* Bitmap of columns used for indexing */
Bitmask extraCols; /* Bitmap of additional columns */
/* Generate code to skip over the creation and initialization of the
** transient index on 2nd and subsequent iterations of the loop. */
v = pParse->pVdbe;
assert( v!=0 );
regIsInit = ++pParse->nMem;
addrInit = sqlite3VdbeAddOp1(v, OP_If, regIsInit);
sqlite3VdbeAddOp2(v, OP_Integer, 1, regIsInit);
/* Count the number of columns that will be added to the index
** and used to match WHERE clause constraints */
nColumn = 0;
pTable = pSrc->pTab;
pWCEnd = &pWC->a[pWC->nTerm];
idxCols = 0;
for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
if( termCanDriveIndex(pTerm, pSrc, notReady) ){
int iCol = pTerm->u.leftColumn;
Bitmask cMask = iCol>=BMS ? ((Bitmask)1)<<(BMS-1) : ((Bitmask)1)<<iCol;
testcase( iCol==BMS );
testcase( iCol==BMS-1 );
if( (idxCols & cMask)==0 ){
nColumn++;
idxCols |= cMask;
}
}
}
assert( nColumn>0 );
pLevel->plan.nEq = nColumn;
/* Count the number of additional columns needed to create a
** covering index. A "covering index" is an index that contains all
** columns that are needed by the query. With a covering index, the
** original table never needs to be accessed. Automatic indices must
** be a covering index because the index will not be updated if the
** original table changes and the index and table cannot both be used
** if they go out of sync.
*/
extraCols = pSrc->colUsed & (~idxCols | (((Bitmask)1)<<(BMS-1)));
mxBitCol = (pTable->nCol >= BMS-1) ? BMS-1 : pTable->nCol;
testcase( pTable->nCol==BMS-1 );
testcase( pTable->nCol==BMS-2 );
for(i=0; i<mxBitCol; i++){
if( extraCols & (((Bitmask)1)<<i) ) nColumn++;
}
if( pSrc->colUsed & (((Bitmask)1)<<(BMS-1)) ){
nColumn += pTable->nCol - BMS + 1;
}
pLevel->plan.wsFlags |= WHERE_COLUMN_EQ | WHERE_IDX_ONLY | WO_EQ;
/* Construct the Index object to describe this index */
nByte = sizeof(Index);
nByte += nColumn*sizeof(int); /* Index.aiColumn */
nByte += nColumn*sizeof(char*); /* Index.azColl */
nByte += nColumn; /* Index.aSortOrder */
pIdx = sqlite3DbMallocZero(pParse->db, nByte);
if( pIdx==0 ) return;
pLevel->plan.u.pIdx = pIdx;
pIdx->azColl = (char**)&pIdx[1];
pIdx->aiColumn = (int*)&pIdx->azColl[nColumn];
pIdx->aSortOrder = (u8*)&pIdx->aiColumn[nColumn];
pIdx->zName = "auto-index";
pIdx->nColumn = nColumn;
pIdx->pTable = pTable;
n = 0;
idxCols = 0;
for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
if( termCanDriveIndex(pTerm, pSrc, notReady) ){
int iCol = pTerm->u.leftColumn;
Bitmask cMask = iCol>=BMS ? ((Bitmask)1)<<(BMS-1) : ((Bitmask)1)<<iCol;
if( (idxCols & cMask)==0 ){
Expr *pX = pTerm->pExpr;
idxCols |= cMask;
pIdx->aiColumn[n] = pTerm->u.leftColumn;
pColl = sqlite3BinaryCompareCollSeq(pParse, pX->pLeft, pX->pRight);
pIdx->azColl[n] = ALWAYS(pColl) ? pColl->zName : "BINARY";
n++;
}
}
}
assert( (u32)n==pLevel->plan.nEq );
/* Add additional columns needed to make the automatic index into
** a covering index */
for(i=0; i<mxBitCol; i++){
if( extraCols & (((Bitmask)1)<<i) ){
pIdx->aiColumn[n] = i;
pIdx->azColl[n] = "BINARY";
n++;
}
}
if( pSrc->colUsed & (((Bitmask)1)<<(BMS-1)) ){
for(i=BMS-1; i<pTable->nCol; i++){
pIdx->aiColumn[n] = i;
pIdx->azColl[n] = "BINARY";
n++;
}
}
assert( n==nColumn );
/* Create the automatic index */
pKeyinfo = sqlite3IndexKeyinfo(pParse, pIdx);
assert( pLevel->iIdxCur>=0 );
sqlite3VdbeAddOp4(v, OP_OpenAutoindex, pLevel->iIdxCur, nColumn+1, 0,
(char*)pKeyinfo, P4_KEYINFO_HANDOFF);
VdbeComment((v, "for %s", pTable->zName));
/* Fill the automatic index with content */
addrTop = sqlite3VdbeAddOp1(v, OP_Rewind, pLevel->iTabCur);
regRecord = sqlite3GetTempReg(pParse);
sqlite3GenerateIndexKey(pParse, pIdx, pLevel->iTabCur, regRecord, 1);
sqlite3VdbeAddOp2(v, OP_IdxInsert, pLevel->iIdxCur, regRecord);
sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
sqlite3VdbeAddOp2(v, OP_Next, pLevel->iTabCur, addrTop+1);
sqlite3VdbeChangeP5(v, SQLITE_STMTSTATUS_AUTOINDEX);
sqlite3VdbeJumpHere(v, addrTop);
sqlite3ReleaseTempReg(pParse, regRecord);
/* Jump here when skipping the initialization */
sqlite3VdbeJumpHere(v, addrInit);
}
#endif /* SQLITE_OMIT_AUTOMATIC_INDEX */
#ifndef SQLITE_OMIT_VIRTUALTABLE
/*
** Allocate and populate an sqlite3_index_info structure. It is the
** responsibility of the caller to eventually release the structure
** by passing the pointer returned by this function to sqlite3_free().
*/
static sqlite3_index_info *allocateIndexInfo(
Parse *pParse,
WhereClause *pWC,
struct SrcList_item *pSrc,
ExprList *pOrderBy
){
int i, j;
int nTerm;
struct sqlite3_index_constraint *pIdxCons;
struct sqlite3_index_orderby *pIdxOrderBy;
struct sqlite3_index_constraint_usage *pUsage;
WhereTerm *pTerm;
int nOrderBy;
sqlite3_index_info *pIdxInfo;
WHERETRACE(("Recomputing index info for %s...\n", pSrc->pTab->zName));
/* Count the number of possible WHERE clause constraints referring
** to this virtual table */
for(i=nTerm=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
if( pTerm->leftCursor != pSrc->iCursor ) continue;
assert( (pTerm->eOperator&(pTerm->eOperator-1))==0 );
testcase( pTerm->eOperator==WO_IN );
testcase( pTerm->eOperator==WO_ISNULL );
if( pTerm->eOperator & (WO_IN|WO_ISNULL) ) continue;
nTerm++;
}
/* If the ORDER BY clause contains only columns in the current
** virtual table then allocate space for the aOrderBy part of
** the sqlite3_index_info structure.
*/
nOrderBy = 0;
if( pOrderBy ){
for(i=0; i<pOrderBy->nExpr; i++){
Expr *pExpr = pOrderBy->a[i].pExpr;
if( pExpr->op!=TK_COLUMN || pExpr->iTable!=pSrc->iCursor ) break;
}
if( i==pOrderBy->nExpr ){
nOrderBy = pOrderBy->nExpr;
}
}
/* Allocate the sqlite3_index_info structure
*/
pIdxInfo = sqlite3DbMallocZero(pParse->db, sizeof(*pIdxInfo)
+ (sizeof(*pIdxCons) + sizeof(*pUsage))*nTerm
+ sizeof(*pIdxOrderBy)*nOrderBy );
if( pIdxInfo==0 ){
sqlite3ErrorMsg(pParse, "out of memory");
/* (double)0 In case of SQLITE_OMIT_FLOATING_POINT... */
return 0;
}
/* Initialize the structure. The sqlite3_index_info structure contains
** many fields that are declared "const" to prevent xBestIndex from
** changing them. We have to do some funky casting in order to
** initialize those fields.
*/
pIdxCons = (struct sqlite3_index_constraint*)&pIdxInfo[1];
pIdxOrderBy = (struct sqlite3_index_orderby*)&pIdxCons[nTerm];
pUsage = (struct sqlite3_index_constraint_usage*)&pIdxOrderBy[nOrderBy];
*(int*)&pIdxInfo->nConstraint = nTerm;
*(int*)&pIdxInfo->nOrderBy = nOrderBy;
*(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint = pIdxCons;
*(struct sqlite3_index_orderby**)&pIdxInfo->aOrderBy = pIdxOrderBy;
*(struct sqlite3_index_constraint_usage**)&pIdxInfo->aConstraintUsage =
pUsage;
for(i=j=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
if( pTerm->leftCursor != pSrc->iCursor ) continue;
assert( (pTerm->eOperator&(pTerm->eOperator-1))==0 );
testcase( pTerm->eOperator==WO_IN );
testcase( pTerm->eOperator==WO_ISNULL );
if( pTerm->eOperator & (WO_IN|WO_ISNULL) ) continue;
pIdxCons[j].iColumn = pTerm->u.leftColumn;
pIdxCons[j].iTermOffset = i;
pIdxCons[j].op = (u8)pTerm->eOperator;
/* The direct assignment in the previous line is possible only because
** the WO_ and SQLITE_INDEX_CONSTRAINT_ codes are identical. The
** following asserts verify this fact. */
assert( WO_EQ==SQLITE_INDEX_CONSTRAINT_EQ );
assert( WO_LT==SQLITE_INDEX_CONSTRAINT_LT );
assert( WO_LE==SQLITE_INDEX_CONSTRAINT_LE );
assert( WO_GT==SQLITE_INDEX_CONSTRAINT_GT );
assert( WO_GE==SQLITE_INDEX_CONSTRAINT_GE );
assert( WO_MATCH==SQLITE_INDEX_CONSTRAINT_MATCH );
assert( pTerm->eOperator & (WO_EQ|WO_LT|WO_LE|WO_GT|WO_GE|WO_MATCH) );
j++;
}
for(i=0; i<nOrderBy; i++){
Expr *pExpr = pOrderBy->a[i].pExpr;
pIdxOrderBy[i].iColumn = pExpr->iColumn;
pIdxOrderBy[i].desc = pOrderBy->a[i].sortOrder;
}
return pIdxInfo;
}
/*
** The table object reference passed as the second argument to this function
** must represent a virtual table. This function invokes the xBestIndex()
** method of the virtual table with the sqlite3_index_info pointer passed
** as the argument.
**
** If an error occurs, pParse is populated with an error message and a
** non-zero value is returned. Otherwise, 0 is returned and the output
** part of the sqlite3_index_info structure is left populated.
**
** Whether or not an error is returned, it is the responsibility of the
** caller to eventually free p->idxStr if p->needToFreeIdxStr indicates
** that this is required.
*/
static int vtabBestIndex(Parse *pParse, Table *pTab, sqlite3_index_info *p){
sqlite3_vtab *pVtab = sqlite3GetVTable(pParse->db, pTab)->pVtab;
int i;
int rc;
WHERETRACE(("xBestIndex for %s\n", pTab->zName));
TRACE_IDX_INPUTS(p);
rc = pVtab->pModule->xBestIndex(pVtab, p);
TRACE_IDX_OUTPUTS(p);
if( rc!=SQLITE_OK ){
if( rc==SQLITE_NOMEM ){
pParse->db->mallocFailed = 1;
}else if( !pVtab->zErrMsg ){
sqlite3ErrorMsg(pParse, "%s", sqlite3ErrStr(rc));
}else{
sqlite3ErrorMsg(pParse, "%s", pVtab->zErrMsg);
}
}
sqlite3_free(pVtab->zErrMsg);
pVtab->zErrMsg = 0;
for(i=0; i<p->nConstraint; i++){
if( !p->aConstraint[i].usable && p->aConstraintUsage[i].argvIndex>0 ){
sqlite3ErrorMsg(pParse,
"table %s: xBestIndex returned an invalid plan", pTab->zName);
}
}
return pParse->nErr;
}
/*
** Compute the best index for a virtual table.
**
** The best index is computed by the xBestIndex method of the virtual
** table module. This routine is really just a wrapper that sets up
** the sqlite3_index_info structure that is used to communicate with
** xBestIndex.
**
** In a join, this routine might be called multiple times for the
** same virtual table. The sqlite3_index_info structure is created
** and initialized on the first invocation and reused on all subsequent
** invocations. The sqlite3_index_info structure is also used when
** code is generated to access the virtual table. The whereInfoDelete()
** routine takes care of freeing the sqlite3_index_info structure after
** everybody has finished with it.
*/
static void bestVirtualIndex(
Parse *pParse, /* The parsing context */
WhereClause *pWC, /* The WHERE clause */
struct SrcList_item *pSrc, /* The FROM clause term to search */
Bitmask notReady, /* Mask of cursors not available for index */
Bitmask notValid, /* Cursors not valid for any purpose */
ExprList *pOrderBy, /* The order by clause */
WhereCost *pCost, /* Lowest cost query plan */
sqlite3_index_info **ppIdxInfo /* Index information passed to xBestIndex */
){
Table *pTab = pSrc->pTab;
sqlite3_index_info *pIdxInfo;
struct sqlite3_index_constraint *pIdxCons;
struct sqlite3_index_constraint_usage *pUsage;
WhereTerm *pTerm;
int i, j;
int nOrderBy;
double rCost;
/* Make sure wsFlags is initialized to some sane value. Otherwise, if the
** malloc in allocateIndexInfo() fails and this function returns leaving
** wsFlags in an uninitialized state, the caller may behave unpredictably.
*/
memset(pCost, 0, sizeof(*pCost));
pCost->plan.wsFlags = WHERE_VIRTUALTABLE;
/* If the sqlite3_index_info structure has not been previously
** allocated and initialized, then allocate and initialize it now.
*/
pIdxInfo = *ppIdxInfo;
if( pIdxInfo==0 ){
*ppIdxInfo = pIdxInfo = allocateIndexInfo(pParse, pWC, pSrc, pOrderBy);
}
if( pIdxInfo==0 ){
return;
}
/* At this point, the sqlite3_index_info structure that pIdxInfo points
** to will have been initialized, either during the current invocation or
** during some prior invocation. Now we just have to customize the
** details of pIdxInfo for the current invocation and pass it to
** xBestIndex.
*/
/* The module name must be defined. Also, by this point there must
** be a pointer to an sqlite3_vtab structure. Otherwise
** sqlite3ViewGetColumnNames() would have picked up the error.
*/
assert( pTab->azModuleArg && pTab->azModuleArg[0] );
assert( sqlite3GetVTable(pParse->db, pTab) );
/* Set the aConstraint[].usable fields and initialize all
** output variables to zero.
**
** aConstraint[].usable is true for constraints where the right-hand
** side contains only references to tables to the left of the current
** table. In other words, if the constraint is of the form:
**
** column = expr
**
** and we are evaluating a join, then the constraint on column is
** only valid if all tables referenced in expr occur to the left
** of the table containing column.
**
** The aConstraints[] array contains entries for all constraints
** on the current table. That way we only have to compute it once
** even though we might try to pick the best index multiple times.
** For each attempt at picking an index, the order of tables in the
** join might be different so we have to recompute the usable flag
** each time.
*/
pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
pUsage = pIdxInfo->aConstraintUsage;
for(i=0; i<pIdxInfo->nConstraint; i++, pIdxCons++){
j = pIdxCons->iTermOffset;
pTerm = &pWC->a[j];
pIdxCons->usable = (pTerm->prereqRight&notReady) ? 0 : 1;
}
memset(pUsage, 0, sizeof(pUsage[0])*pIdxInfo->nConstraint);
if( pIdxInfo->needToFreeIdxStr ){
sqlite3_free(pIdxInfo->idxStr);
}
pIdxInfo->idxStr = 0;
pIdxInfo->idxNum = 0;
pIdxInfo->needToFreeIdxStr = 0;
pIdxInfo->orderByConsumed = 0;
/* ((double)2) In case of SQLITE_OMIT_FLOATING_POINT... */
pIdxInfo->estimatedCost = SQLITE_BIG_DBL / ((double)2);
nOrderBy = pIdxInfo->nOrderBy;
if( !pOrderBy ){
pIdxInfo->nOrderBy = 0;
}
if( vtabBestIndex(pParse, pTab, pIdxInfo) ){
return;
}
pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
for(i=0; i<pIdxInfo->nConstraint; i++){
if( pUsage[i].argvIndex>0 ){
pCost->used |= pWC->a[pIdxCons[i].iTermOffset].prereqRight;
}
}
/* If there is an ORDER BY clause, and the selected virtual table index
** does not satisfy it, increase the cost of the scan accordingly. This
** matches the processing for non-virtual tables in bestBtreeIndex().
*/
rCost = pIdxInfo->estimatedCost;
if( pOrderBy && pIdxInfo->orderByConsumed==0 ){
rCost += estLog(rCost)*rCost;
}
/* The cost is not allowed to be larger than SQLITE_BIG_DBL (the
** inital value of lowestCost in this loop. If it is, then the
** (cost<lowestCost) test below will never be true.
**
** Use "(double)2" instead of "2.0" in case OMIT_FLOATING_POINT
** is defined.
*/
if( (SQLITE_BIG_DBL/((double)2))<rCost ){
pCost->rCost = (SQLITE_BIG_DBL/((double)2));
}else{
pCost->rCost = rCost;
}
pCost->plan.u.pVtabIdx = pIdxInfo;
if( pIdxInfo->orderByConsumed ){
pCost->plan.wsFlags |= WHERE_ORDERBY;
}
pCost->plan.nEq = 0;
pIdxInfo->nOrderBy = nOrderBy;
/* Try to find a more efficient access pattern by using multiple indexes
** to optimize an OR expression within the WHERE clause.
*/
bestOrClauseIndex(pParse, pWC, pSrc, notReady, notValid, pOrderBy, pCost);
}
#endif /* SQLITE_OMIT_VIRTUALTABLE */
/*
** Argument pIdx is a pointer to an index structure that has an array of
** SQLITE_INDEX_SAMPLES evenly spaced samples of the first indexed column
** stored in Index.aSample. These samples divide the domain of values stored
** the index into (SQLITE_INDEX_SAMPLES+1) regions.
** Region 0 contains all values less than the first sample value. Region
** 1 contains values between the first and second samples. Region 2 contains
** values between samples 2 and 3. And so on. Region SQLITE_INDEX_SAMPLES
** contains values larger than the last sample.
**
** If the index contains many duplicates of a single value, then it is
** possible that two or more adjacent samples can hold the same value.
** When that is the case, the smallest possible region code is returned
** when roundUp is false and the largest possible region code is returned
** when roundUp is true.
**
** If successful, this function determines which of the regions value
** pVal lies in, sets *piRegion to the region index (a value between 0
** and SQLITE_INDEX_SAMPLES+1, inclusive) and returns SQLITE_OK.
** Or, if an OOM occurs while converting text values between encodings,
** SQLITE_NOMEM is returned and *piRegion is undefined.
*/
#ifdef SQLITE_ENABLE_STAT2
static int whereRangeRegion(
Parse *pParse, /* Database connection */
Index *pIdx, /* Index to consider domain of */
sqlite3_value *pVal, /* Value to consider */
int roundUp, /* Return largest valid region if true */
int *piRegion /* OUT: Region of domain in which value lies */
){
assert( roundUp==0 || roundUp==1 );
if( ALWAYS(pVal) ){
IndexSample *aSample = pIdx->aSample;
int i = 0;
int eType = sqlite3_value_type(pVal);
if( eType==SQLITE_INTEGER || eType==SQLITE_FLOAT ){
double r = sqlite3_value_double(pVal);
for(i=0; i<SQLITE_INDEX_SAMPLES; i++){
if( aSample[i].eType==SQLITE_NULL ) continue;
if( aSample[i].eType>=SQLITE_TEXT ) break;
if( roundUp ){
if( aSample[i].u.r>r ) break;
}else{
if( aSample[i].u.r>=r ) break;
}
}
}else if( eType==SQLITE_NULL ){
i = 0;
if( roundUp ){
while( i<SQLITE_INDEX_SAMPLES && aSample[i].eType==SQLITE_NULL ) i++;
}
}else{
sqlite3 *db = pParse->db;
CollSeq *pColl;
const u8 *z;
int n;
/* pVal comes from sqlite3ValueFromExpr() so the type cannot be NULL */
assert( eType==SQLITE_TEXT || eType==SQLITE_BLOB );
if( eType==SQLITE_BLOB ){
z = (const u8 *)sqlite3_value_blob(pVal);
pColl = db->pDfltColl;
assert( pColl->enc==SQLITE_UTF8 );
}else{
pColl = sqlite3GetCollSeq(db, SQLITE_UTF8, 0, *pIdx->azColl);
if( pColl==0 ){
sqlite3ErrorMsg(pParse, "no such collation sequence: %s",
*pIdx->azColl);
return SQLITE_ERROR;
}
z = (const u8 *)sqlite3ValueText(pVal, pColl->enc);
if( !z ){
return SQLITE_NOMEM;
}
assert( z && pColl && pColl->xCmp );
}
n = sqlite3ValueBytes(pVal, pColl->enc);
for(i=0; i<SQLITE_INDEX_SAMPLES; i++){
int c;
int eSampletype = aSample[i].eType;
if( eSampletype==SQLITE_NULL || eSampletype<eType ) continue;
if( (eSampletype!=eType) ) break;
#ifndef SQLITE_OMIT_UTF16
if( pColl->enc!=SQLITE_UTF8 ){
int nSample;
char *zSample = sqlite3Utf8to16(
db, pColl->enc, aSample[i].u.z, aSample[i].nByte, &nSample
);
if( !zSample ){
assert( db->mallocFailed );
return SQLITE_NOMEM;
}
c = pColl->xCmp(pColl->pUser, nSample, zSample, n, z);
sqlite3DbFree(db, zSample);
}else
#endif
{
c = pColl->xCmp(pColl->pUser, aSample[i].nByte, aSample[i].u.z, n, z);
}
if( c-roundUp>=0 ) break;
}
}
assert( i>=0 && i<=SQLITE_INDEX_SAMPLES );
*piRegion = i;
}
return SQLITE_OK;
}
#endif /* #ifdef SQLITE_ENABLE_STAT2 */
/*
** If expression pExpr represents a literal value, set *pp to point to
** an sqlite3_value structure containing the same value, with affinity
** aff applied to it, before returning. It is the responsibility of the
** caller to eventually release this structure by passing it to
** sqlite3ValueFree().
**
** If the current parse is a recompile (sqlite3Reprepare()) and pExpr
** is an SQL variable that currently has a non-NULL value bound to it,
** create an sqlite3_value structure containing this value, again with
** affinity aff applied to it, instead.
**
** If neither of the above apply, set *pp to NULL.
**
** If an error occurs, return an error code. Otherwise, SQLITE_OK.
*/
#ifdef SQLITE_ENABLE_STAT2
static int valueFromExpr(
Parse *pParse,
Expr *pExpr,
u8 aff,
sqlite3_value **pp
){
if( pExpr->op==TK_VARIABLE
|| (pExpr->op==TK_REGISTER && pExpr->op2==TK_VARIABLE)
){
int iVar = pExpr->iColumn;
sqlite3VdbeSetVarmask(pParse->pVdbe, iVar); /* IMP: R-23257-02778 */
*pp = sqlite3VdbeGetValue(pParse->pReprepare, iVar, aff);
return SQLITE_OK;
}
return sqlite3ValueFromExpr(pParse->db, pExpr, SQLITE_UTF8, aff, pp);
}
#endif
/*
** This function is used to estimate the number of rows that will be visited
** by scanning an index for a range of values. The range may have an upper
** bound, a lower bound, or both. The WHERE clause terms that set the upper
** and lower bounds are represented by pLower and pUpper respectively. For
** example, assuming that index p is on t1(a):
**
** ... FROM t1 WHERE a > ? AND a < ? ...
** |_____| |_____|
** | |
** pLower pUpper
**
** If either of the upper or lower bound is not present, then NULL is passed in
** place of the corresponding WhereTerm.
**
** The nEq parameter is passed the index of the index column subject to the
** range constraint. Or, equivalently, the number of equality constraints
** optimized by the proposed index scan. For example, assuming index p is
** on t1(a, b), and the SQL query is:
**
** ... FROM t1 WHERE a = ? AND b > ? AND b < ? ...
**
** then nEq should be passed the value 1 (as the range restricted column,
** b, is the second left-most column of the index). Or, if the query is:
**
** ... FROM t1 WHERE a > ? AND a < ? ...
**
** then nEq should be passed 0.
**
** The returned value is an integer between 1 and 100, inclusive. A return
** value of 1 indicates that the proposed range scan is expected to visit
** approximately 1/100th (1%) of the rows selected by the nEq equality
** constraints (if any). A return value of 100 indicates that it is expected
** that the range scan will visit every row (100%) selected by the equality
** constraints.
**
** In the absence of sqlite_stat2 ANALYZE data, each range inequality
** reduces the search space by 3/4ths. Hence a single constraint (x>?)
** results in a return of 25 and a range constraint (x>? AND x<?) results
** in a return of 6.
*/
static int whereRangeScanEst(
Parse *pParse, /* Parsing & code generating context */
Index *p, /* The index containing the range-compared column; "x" */
int nEq, /* index into p->aCol[] of the range-compared column */
WhereTerm *pLower, /* Lower bound on the range. ex: "x>123" Might be NULL */
WhereTerm *pUpper, /* Upper bound on the range. ex: "x<455" Might be NULL */
int *piEst /* OUT: Return value */
){
int rc = SQLITE_OK;
#ifdef SQLITE_ENABLE_STAT2
if( nEq==0 && p->aSample ){
sqlite3_value *pLowerVal = 0;
sqlite3_value *pUpperVal = 0;
int iEst;
int iLower = 0;
int iUpper = SQLITE_INDEX_SAMPLES;
int roundUpUpper = 0;
int roundUpLower = 0;
u8 aff = p->pTable->aCol[p->aiColumn[0]].affinity;
if( pLower ){
Expr *pExpr = pLower->pExpr->pRight;
rc = valueFromExpr(pParse, pExpr, aff, &pLowerVal);
assert( pLower->eOperator==WO_GT || pLower->eOperator==WO_GE );
roundUpLower = (pLower->eOperator==WO_GT) ?1:0;
}
if( rc==SQLITE_OK && pUpper ){
Expr *pExpr = pUpper->pExpr->pRight;
rc = valueFromExpr(pParse, pExpr, aff, &pUpperVal);
assert( pUpper->eOperator==WO_LT || pUpper->eOperator==WO_LE );
roundUpUpper = (pUpper->eOperator==WO_LE) ?1:0;
}
if( rc!=SQLITE_OK || (pLowerVal==0 && pUpperVal==0) ){
sqlite3ValueFree(pLowerVal);
sqlite3ValueFree(pUpperVal);
goto range_est_fallback;
}else if( pLowerVal==0 ){
rc = whereRangeRegion(pParse, p, pUpperVal, roundUpUpper, &iUpper);
if( pLower ) iLower = iUpper/2;
}else if( pUpperVal==0 ){
rc = whereRangeRegion(pParse, p, pLowerVal, roundUpLower, &iLower);
if( pUpper ) iUpper = (iLower + SQLITE_INDEX_SAMPLES + 1)/2;
}else{
rc = whereRangeRegion(pParse, p, pUpperVal, roundUpUpper, &iUpper);
if( rc==SQLITE_OK ){
rc = whereRangeRegion(pParse, p, pLowerVal, roundUpLower, &iLower);
}
}
WHERETRACE(("range scan regions: %d..%d\n", iLower, iUpper));
iEst = iUpper - iLower;
testcase( iEst==SQLITE_INDEX_SAMPLES );
assert( iEst<=SQLITE_INDEX_SAMPLES );
if( iEst<1 ){
*piEst = 50/SQLITE_INDEX_SAMPLES;
}else{
*piEst = (iEst*100)/SQLITE_INDEX_SAMPLES;
}
sqlite3ValueFree(pLowerVal);
sqlite3ValueFree(pUpperVal);
return rc;
}
range_est_fallback:
#else
UNUSED_PARAMETER(pParse);
UNUSED_PARAMETER(p);
UNUSED_PARAMETER(nEq);
#endif
assert( pLower || pUpper );
*piEst = 100;
if( pLower && (pLower->wtFlags & TERM_VNULL)==0 ) *piEst /= 4;
if( pUpper ) *piEst /= 4;
return rc;
}
#ifdef SQLITE_ENABLE_STAT2
/*
** Estimate the number of rows that will be returned based on
** an equality constraint x=VALUE and where that VALUE occurs in
** the histogram data. This only works when x is the left-most
** column of an index and sqlite_stat2 histogram data is available
** for that index. When pExpr==NULL that means the constraint is
** "x IS NULL" instead of "x=VALUE".
**
** Write the estimated row count into *pnRow and return SQLITE_OK.
** If unable to make an estimate, leave *pnRow unchanged and return
** non-zero.
**
** This routine can fail if it is unable to load a collating sequence
** required for string comparison, or if unable to allocate memory
** for a UTF conversion required for comparison. The error is stored
** in the pParse structure.
*/
static int whereEqualScanEst(
Parse *pParse, /* Parsing & code generating context */
Index *p, /* The index whose left-most column is pTerm */
Expr *pExpr, /* Expression for VALUE in the x=VALUE constraint */
double *pnRow /* Write the revised row estimate here */
){
sqlite3_value *pRhs = 0; /* VALUE on right-hand side of pTerm */
int iLower, iUpper; /* Range of histogram regions containing pRhs */
u8 aff; /* Column affinity */
int rc; /* Subfunction return code */
double nRowEst; /* New estimate of the number of rows */
assert( p->aSample!=0 );
aff = p->pTable->aCol[p->aiColumn[0]].affinity;
if( pExpr ){
rc = valueFromExpr(pParse, pExpr, aff, &pRhs);
if( rc ) goto whereEqualScanEst_cancel;
}else{
pRhs = sqlite3ValueNew(pParse->db);
}
if( pRhs==0 ) return SQLITE_NOTFOUND;
rc = whereRangeRegion(pParse, p, pRhs, 0, &iLower);
if( rc ) goto whereEqualScanEst_cancel;
rc = whereRangeRegion(pParse, p, pRhs, 1, &iUpper);
if( rc ) goto whereEqualScanEst_cancel;
WHERETRACE(("equality scan regions: %d..%d\n", iLower, iUpper));
if( iLower>=iUpper ){
nRowEst = p->aiRowEst[0]/(SQLITE_INDEX_SAMPLES*2);
if( nRowEst<*pnRow ) *pnRow = nRowEst;
}else{
nRowEst = (iUpper-iLower)*p->aiRowEst[0]/SQLITE_INDEX_SAMPLES;
*pnRow = nRowEst;
}
whereEqualScanEst_cancel:
sqlite3ValueFree(pRhs);
return rc;
}
#endif /* defined(SQLITE_ENABLE_STAT2) */
#ifdef SQLITE_ENABLE_STAT2
/*
** Estimate the number of rows that will be returned based on
** an IN constraint where the right-hand side of the IN operator
** is a list of values. Example:
**
** WHERE x IN (1,2,3,4)
**
** Write the estimated row count into *pnRow and return SQLITE_OK.
** If unable to make an estimate, leave *pnRow unchanged and return
** non-zero.
**
** This routine can fail if it is unable to load a collating sequence
** required for string comparison, or if unable to allocate memory
** for a UTF conversion required for comparison. The error is stored
** in the pParse structure.
*/
static int whereInScanEst(
Parse *pParse, /* Parsing & code generating context */
Index *p, /* The index whose left-most column is pTerm */
ExprList *pList, /* The value list on the RHS of "x IN (v1,v2,v3,...)" */
double *pnRow /* Write the revised row estimate here */
){
sqlite3_value *pVal = 0; /* One value from list */
int iLower, iUpper; /* Range of histogram regions containing pRhs */
u8 aff; /* Column affinity */
int rc = SQLITE_OK; /* Subfunction return code */
double nRowEst; /* New estimate of the number of rows */
int nSpan = 0; /* Number of histogram regions spanned */
int nSingle = 0; /* Histogram regions hit by a single value */
int nNotFound = 0; /* Count of values that are not constants */
int i; /* Loop counter */
u8 aSpan[SQLITE_INDEX_SAMPLES+1]; /* Histogram regions that are spanned */
u8 aSingle[SQLITE_INDEX_SAMPLES+1]; /* Histogram regions hit once */
assert( p->aSample!=0 );
aff = p->pTable->aCol[p->aiColumn[0]].affinity;
memset(aSpan, 0, sizeof(aSpan));
memset(aSingle, 0, sizeof(aSingle));
for(i=0; i<pList->nExpr; i++){
sqlite3ValueFree(pVal);
rc = valueFromExpr(pParse, pList->a[i].pExpr, aff, &pVal);
if( rc ) break;
if( pVal==0 || sqlite3_value_type(pVal)==SQLITE_NULL ){
nNotFound++;
continue;
}
rc = whereRangeRegion(pParse, p, pVal, 0, &iLower);
if( rc ) break;
rc = whereRangeRegion(pParse, p, pVal, 1, &iUpper);
if( rc ) break;
if( iLower>=iUpper ){
aSingle[iLower] = 1;
}else{
assert( iLower>=0 && iUpper<=SQLITE_INDEX_SAMPLES );
while( iLower<iUpper ) aSpan[iLower++] = 1;
}
}
if( rc==SQLITE_OK ){
for(i=nSpan=0; i<=SQLITE_INDEX_SAMPLES; i++){
if( aSpan[i] ){
nSpan++;
}else if( aSingle[i] ){
nSingle++;
}
}
nRowEst = (nSpan*2+nSingle)*p->aiRowEst[0]/(2*SQLITE_INDEX_SAMPLES)
+ nNotFound*p->aiRowEst[1];
if( nRowEst > p->aiRowEst[0] ) nRowEst = p->aiRowEst[0];
*pnRow = nRowEst;
WHERETRACE(("IN row estimate: nSpan=%d, nSingle=%d, nNotFound=%d, est=%g\n",
nSpan, nSingle, nNotFound, nRowEst));
}
sqlite3ValueFree(pVal);
return rc;
}
#endif /* defined(SQLITE_ENABLE_STAT2) */
/*
** Find the best query plan for accessing a particular table. Write the
** best query plan and its cost into the WhereCost object supplied as the
** last parameter.
**
** The lowest cost plan wins. The cost is an estimate of the amount of
** CPU and disk I/O needed to process the requested result.
** Factors that influence cost include:
**
** * The estimated number of rows that will be retrieved. (The
** fewer the better.)
**
** * Whether or not sorting must occur.
**
** * Whether or not there must be separate lookups in the
** index and in the main table.
**
** If there was an INDEXED BY clause (pSrc->pIndex) attached to the table in
** the SQL statement, then this function only considers plans using the
** named index. If no such plan is found, then the returned cost is
** SQLITE_BIG_DBL. If a plan is found that uses the named index,
** then the cost is calculated in the usual way.
**
** If a NOT INDEXED clause (pSrc->notIndexed!=0) was attached to the table
** in the SELECT statement, then no indexes are considered. However, the
** selected plan may still take advantage of the built-in rowid primary key
** index.
*/
static void bestBtreeIndex(
Parse *pParse, /* The parsing context */
WhereClause *pWC, /* The WHERE clause */
struct SrcList_item *pSrc, /* The FROM clause term to search */
Bitmask notReady, /* Mask of cursors not available for indexing */
Bitmask notValid, /* Cursors not available for any purpose */
ExprList *pOrderBy, /* The ORDER BY clause */
WhereCost *pCost /* Lowest cost query plan */
){
int iCur = pSrc->iCursor; /* The cursor of the table to be accessed */
Index *pProbe; /* An index we are evaluating */
Index *pIdx; /* Copy of pProbe, or zero for IPK index */
int eqTermMask; /* Current mask of valid equality operators */
int idxEqTermMask; /* Index mask of valid equality operators */
Index sPk; /* A fake index object for the primary key */
unsigned int aiRowEstPk[2]; /* The aiRowEst[] value for the sPk index */
int aiColumnPk = -1; /* The aColumn[] value for the sPk index */
int wsFlagMask; /* Allowed flags in pCost->plan.wsFlag */
/* Initialize the cost to a worst-case value */
memset(pCost, 0, sizeof(*pCost));
pCost->rCost = SQLITE_BIG_DBL;
/* If the pSrc table is the right table of a LEFT JOIN then we may not
** use an index to satisfy IS NULL constraints on that table. This is
** because columns might end up being NULL if the table does not match -
** a circumstance which the index cannot help us discover. Ticket #2177.
*/
if( pSrc->jointype & JT_LEFT ){
idxEqTermMask = WO_EQ|WO_IN;
}else{
idxEqTermMask = WO_EQ|WO_IN|WO_ISNULL;
}
if( pSrc->pIndex ){
/* An INDEXED BY clause specifies a particular index to use */
pIdx = pProbe = pSrc->pIndex;
wsFlagMask = ~(WHERE_ROWID_EQ|WHERE_ROWID_RANGE);
eqTermMask = idxEqTermMask;
}else{
/* There is no INDEXED BY clause. Create a fake Index object in local
** variable sPk to represent the rowid primary key index. Make this
** fake index the first in a chain of Index objects with all of the real
** indices to follow */
Index *pFirst; /* First of real indices on the table */
memset(&sPk, 0, sizeof(Index));
sPk.nColumn = 1;
sPk.aiColumn = &aiColumnPk;
sPk.aiRowEst = aiRowEstPk;
sPk.onError = OE_Replace;
sPk.pTable = pSrc->pTab;
aiRowEstPk[0] = pSrc->pTab->nRowEst;
aiRowEstPk[1] = 1;
pFirst = pSrc->pTab->pIndex;
if( pSrc->notIndexed==0 ){
/* The real indices of the table are only considered if the
** NOT INDEXED qualifier is omitted from the FROM clause */
sPk.pNext = pFirst;
}
pProbe = &sPk;
wsFlagMask = ~(
WHERE_COLUMN_IN|WHERE_COLUMN_EQ|WHERE_COLUMN_NULL|WHERE_COLUMN_RANGE
);
eqTermMask = WO_EQ|WO_IN;
pIdx = 0;
}
/* Loop over all indices looking for the best one to use
*/
for(; pProbe; pIdx=pProbe=pProbe->pNext){
const unsigned int * const aiRowEst = pProbe->aiRowEst;
double cost; /* Cost of using pProbe */
double nRow; /* Estimated number of rows in result set */
double log10N; /* base-10 logarithm of nRow (inexact) */
int rev; /* True to scan in reverse order */
int wsFlags = 0;
Bitmask used = 0;
/* The following variables are populated based on the properties of
** index being evaluated. They are then used to determine the expected
** cost and number of rows returned.
**
** nEq:
** Number of equality terms that can be implemented using the index.
** In other words, the number of initial fields in the index that
** are used in == or IN or NOT NULL constraints of the WHERE clause.
**
** nInMul:
** The "in-multiplier". This is an estimate of how many seek operations
** SQLite must perform on the index in question. For example, if the
** WHERE clause is:
**
** WHERE a IN (1, 2, 3) AND b IN (4, 5, 6)
**
** SQLite must perform 9 lookups on an index on (a, b), so nInMul is
** set to 9. Given the same schema and either of the following WHERE
** clauses:
**
** WHERE a = 1
** WHERE a >= 2
**
** nInMul is set to 1.
**
** If there exists a WHERE term of the form "x IN (SELECT ...)", then
** the sub-select is assumed to return 25 rows for the purposes of
** determining nInMul.
**
** bInEst:
** Set to true if there was at least one "x IN (SELECT ...)" term used
** in determining the value of nInMul. Note that the RHS of the
** IN operator must be a SELECT, not a value list, for this variable
** to be true.
**
** estBound:
** An estimate on the amount of the table that must be searched. A
** value of 100 means the entire table is searched. Range constraints
** might reduce this to a value less than 100 to indicate that only
** a fraction of the table needs searching. In the absence of
** sqlite_stat2 ANALYZE data, a single inequality reduces the search
** space to 1/4rd its original size. So an x>? constraint reduces
** estBound to 25. Two constraints (x>? AND x<?) reduce estBound to 6.
**
** bSort:
** Boolean. True if there is an ORDER BY clause that will require an
** external sort (i.e. scanning the index being evaluated will not
** correctly order records).
**
** bLookup:
** Boolean. True if a table lookup is required for each index entry
** visited. In other words, true if this is not a covering index.
** This is always false for the rowid primary key index of a table.
** For other indexes, it is true unless all the columns of the table
** used by the SELECT statement are present in the index (such an
** index is sometimes described as a covering index).
** For example, given the index on (a, b), the second of the following
** two queries requires table b-tree lookups in order to find the value
** of column c, but the first does not because columns a and b are
** both available in the index.
**
** SELECT a, b FROM tbl WHERE a = 1;
** SELECT a, b, c FROM tbl WHERE a = 1;
*/
int nEq; /* Number of == or IN terms matching index */
int bInEst = 0; /* True if "x IN (SELECT...)" seen */
int nInMul = 1; /* Number of distinct equalities to lookup */
int estBound = 100; /* Estimated reduction in search space */
int nBound = 0; /* Number of range constraints seen */
int bSort = 0; /* True if external sort required */
int bLookup = 0; /* True if not a covering index */
WhereTerm *pTerm; /* A single term of the WHERE clause */
#ifdef SQLITE_ENABLE_STAT2
WhereTerm *pFirstTerm = 0; /* First term matching the index */
#endif
/* Determine the values of nEq and nInMul */
for(nEq=0; nEq<pProbe->nColumn; nEq++){
int j = pProbe->aiColumn[nEq];
pTerm = findTerm(pWC, iCur, j, notReady, eqTermMask, pIdx);
if( pTerm==0 ) break;
wsFlags |= (WHERE_COLUMN_EQ|WHERE_ROWID_EQ);
if( pTerm->eOperator & WO_IN ){
Expr *pExpr = pTerm->pExpr;
wsFlags |= WHERE_COLUMN_IN;
if( ExprHasProperty(pExpr, EP_xIsSelect) ){
/* "x IN (SELECT ...)": Assume the SELECT returns 25 rows */
nInMul *= 25;
bInEst = 1;
}else if( ALWAYS(pExpr->x.pList && pExpr->x.pList->nExpr) ){
/* "x IN (value, value, ...)" */
nInMul *= pExpr->x.pList->nExpr;
}
}else if( pTerm->eOperator & WO_ISNULL ){
wsFlags |= WHERE_COLUMN_NULL;
}
#ifdef SQLITE_ENABLE_STAT2
if( nEq==0 && pProbe->aSample ) pFirstTerm = pTerm;
#endif
used |= pTerm->prereqRight;
}
/* Determine the value of estBound. */
if( nEq<pProbe->nColumn && pProbe->bUnordered==0 ){
int j = pProbe->aiColumn[nEq];
if( findTerm(pWC, iCur, j, notReady, WO_LT|WO_LE|WO_GT|WO_GE, pIdx) ){
WhereTerm *pTop = findTerm(pWC, iCur, j, notReady, WO_LT|WO_LE, pIdx);
WhereTerm *pBtm = findTerm(pWC, iCur, j, notReady, WO_GT|WO_GE, pIdx);
whereRangeScanEst(pParse, pProbe, nEq, pBtm, pTop, &estBound);
if( pTop ){
nBound = 1;
wsFlags |= WHERE_TOP_LIMIT;
used |= pTop->prereqRight;
}
if( pBtm ){
nBound++;
wsFlags |= WHERE_BTM_LIMIT;
used |= pBtm->prereqRight;
}
wsFlags |= (WHERE_COLUMN_RANGE|WHERE_ROWID_RANGE);
}
}else if( pProbe->onError!=OE_None ){
testcase( wsFlags & WHERE_COLUMN_IN );
testcase( wsFlags & WHERE_COLUMN_NULL );
if( (wsFlags & (WHERE_COLUMN_IN|WHERE_COLUMN_NULL))==0 ){
wsFlags |= WHERE_UNIQUE;
}
}
/* If there is an ORDER BY clause and the index being considered will
** naturally scan rows in the required order, set the appropriate flags
** in wsFlags. Otherwise, if there is an ORDER BY clause but the index
** will scan rows in a different order, set the bSort variable. */
if( pOrderBy ){
if( (wsFlags & WHERE_COLUMN_IN)==0
&& pProbe->bUnordered==0
&& isSortingIndex(pParse, pWC->pMaskSet, pProbe, iCur, pOrderBy,
nEq, wsFlags, &rev)
){
wsFlags |= WHERE_ROWID_RANGE|WHERE_COLUMN_RANGE|WHERE_ORDERBY;
wsFlags |= (rev ? WHERE_REVERSE : 0);
}else{
bSort = 1;
}
}
/* If currently calculating the cost of using an index (not the IPK
** index), determine if all required column data may be obtained without
** using the main table (i.e. if the index is a covering
** index for this query). If it is, set the WHERE_IDX_ONLY flag in
** wsFlags. Otherwise, set the bLookup variable to true. */
if( pIdx && wsFlags ){
Bitmask m = pSrc->colUsed;
int j;
for(j=0; j<pIdx->nColumn; j++){
int x = pIdx->aiColumn[j];
if( x<BMS-1 ){
m &= ~(((Bitmask)1)<<x);
}
}
if( m==0 ){
wsFlags |= WHERE_IDX_ONLY;
}else{
bLookup = 1;
}
}
/*
** Estimate the number of rows of output. For an "x IN (SELECT...)"
** constraint, do not let the estimate exceed half the rows in the table.
*/
nRow = (double)(aiRowEst[nEq] * nInMul);
if( bInEst && nRow*2>aiRowEst[0] ){
nRow = aiRowEst[0]/2;
nInMul = (int)(nRow / aiRowEst[nEq]);
}
#ifdef SQLITE_ENABLE_STAT2
/* If the constraint is of the form x=VALUE and histogram
** data is available for column x, then it might be possible
** to get a better estimate on the number of rows based on
** VALUE and how common that value is according to the histogram.
*/
if( nRow>(double)1 && nEq==1 && pFirstTerm!=0 ){
if( pFirstTerm->eOperator & (WO_EQ|WO_ISNULL) ){
testcase( pFirstTerm->eOperator==WO_EQ );
testcase( pFirstTerm->eOperator==WO_ISNULL );
whereEqualScanEst(pParse, pProbe, pFirstTerm->pExpr->pRight, &nRow);
}else if( pFirstTerm->eOperator==WO_IN && bInEst==0 ){
whereInScanEst(pParse, pProbe, pFirstTerm->pExpr->x.pList, &nRow);
}
}
#endif /* SQLITE_ENABLE_STAT2 */
/* Adjust the number of output rows and downward to reflect rows
** that are excluded by range constraints.
*/
nRow = (nRow * (double)estBound) / (double)100;
if( nRow<1 ) nRow = 1;
/* Experiments run on real SQLite databases show that the time needed
** to do a binary search to locate a row in a table or index is roughly
** log10(N) times the time to move from one row to the next row within
** a table or index. The actual times can vary, with the size of
** records being an important factor. Both moves and searches are
** slower with larger records, presumably because fewer records fit
** on one page and hence more pages have to be fetched.
**
** The ANALYZE command and the sqlite_stat1 and sqlite_stat2 tables do
** not give us data on the relative sizes of table and index records.
** So this computation assumes table records are about twice as big
** as index records
*/
if( (wsFlags & WHERE_NOT_FULLSCAN)==0 ){
/* The cost of a full table scan is a number of move operations equal
** to the number of rows in the table.
**
** We add an additional 4x penalty to full table scans. This causes
** the cost function to err on the side of choosing an index over
** choosing a full scan. This 4x full-scan penalty is an arguable
** decision and one which we expect to revisit in the future. But
** it seems to be working well enough at the moment.
*/
cost = aiRowEst[0]*4;
}else{
log10N = estLog(aiRowEst[0]);
cost = nRow;
if( pIdx ){
if( bLookup ){
/* For an index lookup followed by a table lookup:
** nInMul index searches to find the start of each index range
** + nRow steps through the index
** + nRow table searches to lookup the table entry using the rowid
*/
cost += (nInMul + nRow)*log10N;
}else{
/* For a covering index:
** nInMul index searches to find the initial entry
** + nRow steps through the index
*/
cost += nInMul*log10N;
}
}else{
/* For a rowid primary key lookup:
** nInMult table searches to find the initial entry for each range
** + nRow steps through the table
*/
cost += nInMul*log10N;
}
}
/* Add in the estimated cost of sorting the result. Actual experimental
** measurements of sorting performance in SQLite show that sorting time
** adds C*N*log10(N) to the cost, where N is the number of rows to be
** sorted and C is a factor between 1.95 and 4.3. We will split the
** difference and select C of 3.0.
*/
if( bSort ){
cost += nRow*estLog(nRow)*3;
}
/**** Cost of using this index has now been computed ****/
/* If there are additional constraints on this table that cannot
** be used with the current index, but which might lower the number
** of output rows, adjust the nRow value accordingly. This only
** matters if the current index is the least costly, so do not bother
** with this step if we already know this index will not be chosen.
** Also, never reduce the output row count below 2 using this step.
**
** It is critical that the notValid mask be used here instead of
** the notReady mask. When computing an "optimal" index, the notReady
** mask will only have one bit set - the bit for the current table.
** The notValid mask, on the other hand, always has all bits set for
** tables that are not in outer loops. If notReady is used here instead
** of notValid, then a optimal index that depends on inner joins loops
** might be selected even when there exists an optimal index that has
** no such dependency.
*/
if( nRow>2 && cost<=pCost->rCost ){
int k; /* Loop counter */
int nSkipEq = nEq; /* Number of == constraints to skip */
int nSkipRange = nBound; /* Number of < constraints to skip */
Bitmask thisTab; /* Bitmap for pSrc */
thisTab = getMask(pWC->pMaskSet, iCur);
for(pTerm=pWC->a, k=pWC->nTerm; nRow>2 && k; k--, pTerm++){
if( pTerm->wtFlags & TERM_VIRTUAL ) continue;
if( (pTerm->prereqAll & notValid)!=thisTab ) continue;
if( pTerm->eOperator & (WO_EQ|WO_IN|WO_ISNULL) ){
if( nSkipEq ){
/* Ignore the first nEq equality matches since the index
** has already accounted for these */
nSkipEq--;
}else{
/* Assume each additional equality match reduces the result
** set size by a factor of 10 */
nRow /= 10;
}
}else if( pTerm->eOperator & (WO_LT|WO_LE|WO_GT|WO_GE) ){
if( nSkipRange ){
/* Ignore the first nSkipRange range constraints since the index
** has already accounted for these */
nSkipRange--;
}else{
/* Assume each additional range constraint reduces the result
** set size by a factor of 3. Indexed range constraints reduce
** the search space by a larger factor: 4. We make indexed range
** more selective intentionally because of the subjective
** observation that indexed range constraints really are more
** selective in practice, on average. */
nRow /= 3;
}
}else if( pTerm->eOperator!=WO_NOOP ){
/* Any other expression lowers the output row count by half */
nRow /= 2;
}
}
if( nRow<2 ) nRow = 2;
}
WHERETRACE((
"%s(%s): nEq=%d nInMul=%d estBound=%d bSort=%d bLookup=%d wsFlags=0x%x\n"
" notReady=0x%llx log10N=%.1f nRow=%.1f cost=%.1f used=0x%llx\n",
pSrc->pTab->zName, (pIdx ? pIdx->zName : "ipk"),
nEq, nInMul, estBound, bSort, bLookup, wsFlags,
notReady, log10N, nRow, cost, used
));
/* If this index is the best we have seen so far, then record this
** index and its cost in the pCost structure.
*/
if( (!pIdx || wsFlags)
&& (cost<pCost->rCost || (cost<=pCost->rCost && nRow<pCost->plan.nRow))
){
pCost->rCost = cost;
pCost->used = used;
pCost->plan.nRow = nRow;
pCost->plan.wsFlags = (wsFlags&wsFlagMask);
pCost->plan.nEq = nEq;
pCost->plan.u.pIdx = pIdx;
}
/* If there was an INDEXED BY clause, then only that one index is
** considered. */
if( pSrc->pIndex ) break;
/* Reset masks for the next index in the loop */
wsFlagMask = ~(WHERE_ROWID_EQ|WHERE_ROWID_RANGE);
eqTermMask = idxEqTermMask;
}
/* If there is no ORDER BY clause and the SQLITE_ReverseOrder flag
** is set, then reverse the order that the index will be scanned
** in. This is used for application testing, to help find cases
** where application behaviour depends on the (undefined) order that
** SQLite outputs rows in in the absence of an ORDER BY clause. */
if( !pOrderBy && pParse->db->flags & SQLITE_ReverseOrder ){
pCost->plan.wsFlags |= WHERE_REVERSE;
}
assert( pOrderBy || (pCost->plan.wsFlags&WHERE_ORDERBY)==0 );
assert( pCost->plan.u.pIdx==0 || (pCost->plan.wsFlags&WHERE_ROWID_EQ)==0 );
assert( pSrc->pIndex==0
|| pCost->plan.u.pIdx==0
|| pCost->plan.u.pIdx==pSrc->pIndex
);
WHERETRACE(("best index is: %s\n",
((pCost->plan.wsFlags & WHERE_NOT_FULLSCAN)==0 ? "none" :
pCost->plan.u.pIdx ? pCost->plan.u.pIdx->zName : "ipk")
));
bestOrClauseIndex(pParse, pWC, pSrc, notReady, notValid, pOrderBy, pCost);
bestAutomaticIndex(pParse, pWC, pSrc, notReady, pCost);
pCost->plan.wsFlags |= eqTermMask;
}
/*
** Find the query plan for accessing table pSrc->pTab. Write the
** best query plan and its cost into the WhereCost object supplied
** as the last parameter. This function may calculate the cost of
** both real and virtual table scans.
*/
static void bestIndex(
Parse *pParse, /* The parsing context */
WhereClause *pWC, /* The WHERE clause */
struct SrcList_item *pSrc, /* The FROM clause term to search */
Bitmask notReady, /* Mask of cursors not available for indexing */
Bitmask notValid, /* Cursors not available for any purpose */
ExprList *pOrderBy, /* The ORDER BY clause */
WhereCost *pCost /* Lowest cost query plan */
){
#ifndef SQLITE_OMIT_VIRTUALTABLE
if( IsVirtual(pSrc->pTab) ){
sqlite3_index_info *p = 0;
bestVirtualIndex(pParse, pWC, pSrc, notReady, notValid, pOrderBy, pCost,&p);
if( p->needToFreeIdxStr ){
sqlite3_free(p->idxStr);
}
sqlite3DbFree(pParse->db, p);
}else
#endif
{
bestBtreeIndex(pParse, pWC, pSrc, notReady, notValid, pOrderBy, pCost);
}
}
/*
** Disable a term in the WHERE clause. Except, do not disable the term
** if it controls a LEFT OUTER JOIN and it did not originate in the ON
** or USING clause of that join.
**
** Consider the term t2.z='ok' in the following queries:
**
** (1) SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x WHERE t2.z='ok'
** (2) SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x AND t2.z='ok'
** (3) SELECT * FROM t1, t2 WHERE t1.a=t2.x AND t2.z='ok'
**
** The t2.z='ok' is disabled in the in (2) because it originates
** in the ON clause. The term is disabled in (3) because it is not part
** of a LEFT OUTER JOIN. In (1), the term is not disabled.
**
** IMPLEMENTATION-OF: R-24597-58655 No tests are done for terms that are
** completely satisfied by indices.
**
** Disabling a term causes that term to not be tested in the inner loop
** of the join. Disabling is an optimization. When terms are satisfied
** by indices, we disable them to prevent redundant tests in the inner
** loop. We would get the correct results if nothing were ever disabled,
** but joins might run a little slower. The trick is to disable as much
** as we can without disabling too much. If we disabled in (1), we'd get
** the wrong answer. See ticket #813.
*/
static void disableTerm(WhereLevel *pLevel, WhereTerm *pTerm){
if( pTerm
&& (pTerm->wtFlags & TERM_CODED)==0
&& (pLevel->iLeftJoin==0 || ExprHasProperty(pTerm->pExpr, EP_FromJoin))
){
pTerm->wtFlags |= TERM_CODED;
if( pTerm->iParent>=0 ){
WhereTerm *pOther = &pTerm->pWC->a[pTerm->iParent];
if( (--pOther->nChild)==0 ){
disableTerm(pLevel, pOther);
}
}
}
}
/*
** Code an OP_Affinity opcode to apply the column affinity string zAff
** to the n registers starting at base.
**
** As an optimization, SQLITE_AFF_NONE entries (which are no-ops) at the
** beginning and end of zAff are ignored. If all entries in zAff are
** SQLITE_AFF_NONE, then no code gets generated.
**
** This routine makes its own copy of zAff so that the caller is free
** to modify zAff after this routine returns.
*/
static void codeApplyAffinity(Parse *pParse, int base, int n, char *zAff){
Vdbe *v = pParse->pVdbe;
if( zAff==0 ){
assert( pParse->db->mallocFailed );
return;
}
assert( v!=0 );
/* Adjust base and n to skip over SQLITE_AFF_NONE entries at the beginning
** and end of the affinity string.
*/
while( n>0 && zAff[0]==SQLITE_AFF_NONE ){
n--;
base++;
zAff++;
}
while( n>1 && zAff[n-1]==SQLITE_AFF_NONE ){
n--;
}
/* Code the OP_Affinity opcode if there is anything left to do. */
if( n>0 ){
sqlite3VdbeAddOp2(v, OP_Affinity, base, n);
sqlite3VdbeChangeP4(v, -1, zAff, n);
sqlite3ExprCacheAffinityChange(pParse, base, n);
}
}
/*
** Generate code for a single equality term of the WHERE clause. An equality
** term can be either X=expr or X IN (...). pTerm is the term to be
** coded.
**
** The current value for the constraint is left in register iReg.
**
** For a constraint of the form X=expr, the expression is evaluated and its
** result is left on the stack. For constraints of the form X IN (...)
** this routine sets up a loop that will iterate over all values of X.
*/
static int codeEqualityTerm(
Parse *pParse, /* The parsing context */
WhereTerm *pTerm, /* The term of the WHERE clause to be coded */
WhereLevel *pLevel, /* When level of the FROM clause we are working on */
int iTarget /* Attempt to leave results in this register */
){
Expr *pX = pTerm->pExpr;
Vdbe *v = pParse->pVdbe;
int iReg; /* Register holding results */
assert( iTarget>0 );
if( pX->op==TK_EQ ){
iReg = sqlite3ExprCodeTarget(pParse, pX->pRight, iTarget);
}else if( pX->op==TK_ISNULL ){
iReg = iTarget;
sqlite3VdbeAddOp2(v, OP_Null, 0, iReg);
#ifndef SQLITE_OMIT_SUBQUERY
}else{
int eType;
int iTab;
struct InLoop *pIn;
assert( pX->op==TK_IN );
iReg = iTarget;
eType = sqlite3FindInIndex(pParse, pX, 0);
iTab = pX->iTable;
sqlite3VdbeAddOp2(v, OP_Rewind, iTab, 0);
assert( pLevel->plan.wsFlags & WHERE_IN_ABLE );
if( pLevel->u.in.nIn==0 ){
pLevel->addrNxt = sqlite3VdbeMakeLabel(v);
}
pLevel->u.in.nIn++;
pLevel->u.in.aInLoop =
sqlite3DbReallocOrFree(pParse->db, pLevel->u.in.aInLoop,
sizeof(pLevel->u.in.aInLoop[0])*pLevel->u.in.nIn);
pIn = pLevel->u.in.aInLoop;
if( pIn ){
pIn += pLevel->u.in.nIn - 1;
pIn->iCur = iTab;
if( eType==IN_INDEX_ROWID ){
pIn->addrInTop = sqlite3VdbeAddOp2(v, OP_Rowid, iTab, iReg);
}else{
pIn->addrInTop = sqlite3VdbeAddOp3(v, OP_Column, iTab, 0, iReg);
}
sqlite3VdbeAddOp1(v, OP_IsNull, iReg);
}else{
pLevel->u.in.nIn = 0;
}
#endif
}
disableTerm(pLevel, pTerm);
return iReg;
}
/*
** Generate code that will evaluate all == and IN constraints for an
** index.
**
** For example, consider table t1(a,b,c,d,e,f) with index i1(a,b,c).
** Suppose the WHERE clause is this: a==5 AND b IN (1,2,3) AND c>5 AND c<10
** The index has as many as three equality constraints, but in this
** example, the third "c" value is an inequality. So only two
** constraints are coded. This routine will generate code to evaluate
** a==5 and b IN (1,2,3). The current values for a and b will be stored
** in consecutive registers and the index of the first register is returned.
**
** In the example above nEq==2. But this subroutine works for any value
** of nEq including 0. If nEq==0, this routine is nearly a no-op.
** The only thing it does is allocate the pLevel->iMem memory cell and
** compute the affinity string.
**
** This routine always allocates at least one memory cell and returns
** the index of that memory cell. The code that
** calls this routine will use that memory cell to store the termination
** key value of the loop. If one or more IN operators appear, then
** this routine allocates an additional nEq memory cells for internal
** use.
**
** Before returning, *pzAff is set to point to a buffer containing a
** copy of the column affinity string of the index allocated using
** sqlite3DbMalloc(). Except, entries in the copy of the string associated
** with equality constraints that use NONE affinity are set to
** SQLITE_AFF_NONE. This is to deal with SQL such as the following:
**
** CREATE TABLE t1(a TEXT PRIMARY KEY, b);
** SELECT ... FROM t1 AS t2, t1 WHERE t1.a = t2.b;
**
** In the example above, the index on t1(a) has TEXT affinity. But since
** the right hand side of the equality constraint (t2.b) has NONE affinity,
** no conversion should be attempted before using a t2.b value as part of
** a key to search the index. Hence the first byte in the returned affinity
** string in this example would be set to SQLITE_AFF_NONE.
*/
static int codeAllEqualityTerms(
Parse *pParse, /* Parsing context */
WhereLevel *pLevel, /* Which nested loop of the FROM we are coding */
WhereClause *pWC, /* The WHERE clause */
Bitmask notReady, /* Which parts of FROM have not yet been coded */
int nExtraReg, /* Number of extra registers to allocate */
char **pzAff /* OUT: Set to point to affinity string */
){
int nEq = pLevel->plan.nEq; /* The number of == or IN constraints to code */
Vdbe *v = pParse->pVdbe; /* The vm under construction */
Index *pIdx; /* The index being used for this loop */
int iCur = pLevel->iTabCur; /* The cursor of the table */
WhereTerm *pTerm; /* A single constraint term */
int j; /* Loop counter */
int regBase; /* Base register */
int nReg; /* Number of registers to allocate */
char *zAff; /* Affinity string to return */
/* This module is only called on query plans that use an index. */
assert( pLevel->plan.wsFlags & WHERE_INDEXED );
pIdx = pLevel->plan.u.pIdx;
/* Figure out how many memory cells we will need then allocate them.
*/
regBase = pParse->nMem + 1;
nReg = pLevel->plan.nEq + nExtraReg;
pParse->nMem += nReg;
zAff = sqlite3DbStrDup(pParse->db, sqlite3IndexAffinityStr(v, pIdx));
if( !zAff ){
pParse->db->mallocFailed = 1;
}
/* Evaluate the equality constraints
*/
assert( pIdx->nColumn>=nEq );
for(j=0; j<nEq; j++){
int r1;
int k = pIdx->aiColumn[j];
pTerm = findTerm(pWC, iCur, k, notReady, pLevel->plan.wsFlags, pIdx);
if( NEVER(pTerm==0) ) break;
/* The following true for indices with redundant columns.
** Ex: CREATE INDEX i1 ON t1(a,b,a); SELECT * FROM t1 WHERE a=0 AND b=0; */
testcase( (pTerm->wtFlags & TERM_CODED)!=0 );
testcase( pTerm->wtFlags & TERM_VIRTUAL ); /* EV: R-30575-11662 */
r1 = codeEqualityTerm(pParse, pTerm, pLevel, regBase+j);
if( r1!=regBase+j ){
if( nReg==1 ){
sqlite3ReleaseTempReg(pParse, regBase);
regBase = r1;
}else{
sqlite3VdbeAddOp2(v, OP_SCopy, r1, regBase+j);
}
}
testcase( pTerm->eOperator & WO_ISNULL );
testcase( pTerm->eOperator & WO_IN );
if( (pTerm->eOperator & (WO_ISNULL|WO_IN))==0 ){
Expr *pRight = pTerm->pExpr->pRight;
sqlite3ExprCodeIsNullJump(v, pRight, regBase+j, pLevel->addrBrk);
if( zAff ){
if( sqlite3CompareAffinity(pRight, zAff[j])==SQLITE_AFF_NONE ){
zAff[j] = SQLITE_AFF_NONE;
}
if( sqlite3ExprNeedsNoAffinityChange(pRight, zAff[j]) ){
zAff[j] = SQLITE_AFF_NONE;
}
}
}
}
*pzAff = zAff;
return regBase;
}
#ifndef SQLITE_OMIT_EXPLAIN
/*
** This routine is a helper for explainIndexRange() below
**
** pStr holds the text of an expression that we are building up one term
** at a time. This routine adds a new term to the end of the expression.
** Terms are separated by AND so add the "AND" text for second and subsequent
** terms only.
*/
static void explainAppendTerm(
StrAccum *pStr, /* The text expression being built */
int iTerm, /* Index of this term. First is zero */
const char *zColumn, /* Name of the column */
const char *zOp /* Name of the operator */
){
if( iTerm ) sqlite3StrAccumAppend(pStr, " AND ", 5);
sqlite3StrAccumAppend(pStr, zColumn, -1);
sqlite3StrAccumAppend(pStr, zOp, 1);
sqlite3StrAccumAppend(pStr, "?", 1);
}
/*
** Argument pLevel describes a strategy for scanning table pTab. This
** function returns a pointer to a string buffer containing a description
** of the subset of table rows scanned by the strategy in the form of an
** SQL expression. Or, if all rows are scanned, NULL is returned.
**
** For example, if the query:
**
** SELECT * FROM t1 WHERE a=1 AND b>2;
**
** is run and there is an index on (a, b), then this function returns a
** string similar to:
**
** "a=? AND b>?"
**
** The returned pointer points to memory obtained from sqlite3DbMalloc().
** It is the responsibility of the caller to free the buffer when it is
** no longer required.
*/
static char *explainIndexRange(sqlite3 *db, WhereLevel *pLevel, Table *pTab){
WherePlan *pPlan = &pLevel->plan;
Index *pIndex = pPlan->u.pIdx;
int nEq = pPlan->nEq;
int i, j;
Column *aCol = pTab->aCol;
int *aiColumn = pIndex->aiColumn;
StrAccum txt;
if( nEq==0 && (pPlan->wsFlags & (WHERE_BTM_LIMIT|WHERE_TOP_LIMIT))==0 ){
return 0;
}
sqlite3StrAccumInit(&txt, 0, 0, SQLITE_MAX_LENGTH);
txt.db = db;
sqlite3StrAccumAppend(&txt, " (", 2);
for(i=0; i<nEq; i++){
explainAppendTerm(&txt, i, aCol[aiColumn[i]].zName, "=");
}
j = i;
if( pPlan->wsFlags&WHERE_BTM_LIMIT ){
explainAppendTerm(&txt, i++, aCol[aiColumn[j]].zName, ">");
}
if( pPlan->wsFlags&WHERE_TOP_LIMIT ){
explainAppendTerm(&txt, i, aCol[aiColumn[j]].zName, "<");
}
sqlite3StrAccumAppend(&txt, ")", 1);
return sqlite3StrAccumFinish(&txt);
}
/*
** This function is a no-op unless currently processing an EXPLAIN QUERY PLAN
** command. If the query being compiled is an EXPLAIN QUERY PLAN, a single
** record is added to the output to describe the table scan strategy in
** pLevel.
*/
static void explainOneScan(
Parse *pParse, /* Parse context */
SrcList *pTabList, /* Table list this loop refers to */
WhereLevel *pLevel, /* Scan to write OP_Explain opcode for */
int iLevel, /* Value for "level" column of output */
int iFrom, /* Value for "from" column of output */
u16 wctrlFlags /* Flags passed to sqlite3WhereBegin() */
){
if( pParse->explain==2 ){
u32 flags = pLevel->plan.wsFlags;
struct SrcList_item *pItem = &pTabList->a[pLevel->iFrom];
Vdbe *v = pParse->pVdbe; /* VM being constructed */
sqlite3 *db = pParse->db; /* Database handle */
char *zMsg; /* Text to add to EQP output */
sqlite3_int64 nRow; /* Expected number of rows visited by scan */
int iId = pParse->iSelectId; /* Select id (left-most output column) */
int isSearch; /* True for a SEARCH. False for SCAN. */
if( (flags&WHERE_MULTI_OR) || (wctrlFlags&WHERE_ONETABLE_ONLY) ) return;
isSearch = (pLevel->plan.nEq>0)
|| (flags&(WHERE_BTM_LIMIT|WHERE_TOP_LIMIT))!=0
|| (wctrlFlags&(WHERE_ORDERBY_MIN|WHERE_ORDERBY_MAX));
zMsg = sqlite3MPrintf(db, "%s", isSearch?"SEARCH":"SCAN");
if( pItem->pSelect ){
zMsg = sqlite3MAppendf(db, zMsg, "%s SUBQUERY %d", zMsg,pItem->iSelectId);
}else{
zMsg = sqlite3MAppendf(db, zMsg, "%s TABLE %s", zMsg, pItem->zName);
}
if( pItem->zAlias ){
zMsg = sqlite3MAppendf(db, zMsg, "%s AS %s", zMsg, pItem->zAlias);
}
if( (flags & WHERE_INDEXED)!=0 ){
char *zWhere = explainIndexRange(db, pLevel, pItem->pTab);
zMsg = sqlite3MAppendf(db, zMsg, "%s USING %s%sINDEX%s%s%s", zMsg,
((flags & WHERE_TEMP_INDEX)?"AUTOMATIC ":""),
((flags & WHERE_IDX_ONLY)?"COVERING ":""),
((flags & WHERE_TEMP_INDEX)?"":" "),
((flags & WHERE_TEMP_INDEX)?"": pLevel->plan.u.pIdx->zName),
zWhere
);
sqlite3DbFree(db, zWhere);
}else if( flags & (WHERE_ROWID_EQ|WHERE_ROWID_RANGE) ){
zMsg = sqlite3MAppendf(db, zMsg, "%s USING INTEGER PRIMARY KEY", zMsg);
if( flags&WHERE_ROWID_EQ ){
zMsg = sqlite3MAppendf(db, zMsg, "%s (rowid=?)", zMsg);
}else if( (flags&WHERE_BOTH_LIMIT)==WHERE_BOTH_LIMIT ){
zMsg = sqlite3MAppendf(db, zMsg, "%s (rowid>? AND rowid<?)", zMsg);
}else if( flags&WHERE_BTM_LIMIT ){
zMsg = sqlite3MAppendf(db, zMsg, "%s (rowid>?)", zMsg);
}else if( flags&WHERE_TOP_LIMIT ){
zMsg = sqlite3MAppendf(db, zMsg, "%s (rowid<?)", zMsg);
}
}
#ifndef SQLITE_OMIT_VIRTUALTABLE
else if( (flags & WHERE_VIRTUALTABLE)!=0 ){
sqlite3_index_info *pVtabIdx = pLevel->plan.u.pVtabIdx;
zMsg = sqlite3MAppendf(db, zMsg, "%s VIRTUAL TABLE INDEX %d:%s", zMsg,
pVtabIdx->idxNum, pVtabIdx->idxStr);
}
#endif
if( wctrlFlags&(WHERE_ORDERBY_MIN|WHERE_ORDERBY_MAX) ){
testcase( wctrlFlags & WHERE_ORDERBY_MIN );
nRow = 1;
}else{
nRow = (sqlite3_int64)pLevel->plan.nRow;
}
zMsg = sqlite3MAppendf(db, zMsg, "%s (~%lld rows)", zMsg, nRow);
sqlite3VdbeAddOp4(v, OP_Explain, iId, iLevel, iFrom, zMsg, P4_DYNAMIC);
}
}
#else
# define explainOneScan(u,v,w,x,y,z)
#endif /* SQLITE_OMIT_EXPLAIN */
/*
** Generate code for the start of the iLevel-th loop in the WHERE clause
** implementation described by pWInfo.
*/
static Bitmask codeOneLoopStart(
WhereInfo *pWInfo, /* Complete information about the WHERE clause */
int iLevel, /* Which level of pWInfo->a[] should be coded */
u16 wctrlFlags, /* One of the WHERE_* flags defined in sqliteInt.h */
Bitmask notReady /* Which tables are currently available */
){
int j, k; /* Loop counters */
int iCur; /* The VDBE cursor for the table */
int addrNxt; /* Where to jump to continue with the next IN case */
int omitTable; /* True if we use the index only */
int bRev; /* True if we need to scan in reverse order */
WhereLevel *pLevel; /* The where level to be coded */
WhereClause *pWC; /* Decomposition of the entire WHERE clause */
WhereTerm *pTerm; /* A WHERE clause term */
Parse *pParse; /* Parsing context */
Vdbe *v; /* The prepared stmt under constructions */
struct SrcList_item *pTabItem; /* FROM clause term being coded */
int addrBrk; /* Jump here to break out of the loop */
int addrCont; /* Jump here to continue with next cycle */
int iRowidReg = 0; /* Rowid is stored in this register, if not zero */
int iReleaseReg = 0; /* Temp register to free before returning */
pParse = pWInfo->pParse;
v = pParse->pVdbe;
pWC = pWInfo->pWC;
pLevel = &pWInfo->a[iLevel];
pTabItem = &pWInfo->pTabList->a[pLevel->iFrom];
iCur = pTabItem->iCursor;
bRev = (pLevel->plan.wsFlags & WHERE_REVERSE)!=0;
omitTable = (pLevel->plan.wsFlags & WHERE_IDX_ONLY)!=0
&& (wctrlFlags & WHERE_FORCE_TABLE)==0;
/* Create labels for the "break" and "continue" instructions
** for the current loop. Jump to addrBrk to break out of a loop.
** Jump to cont to go immediately to the next iteration of the
** loop.
**
** When there is an IN operator, we also have a "addrNxt" label that
** means to continue with the next IN value combination. When
** there are no IN operators in the constraints, the "addrNxt" label
** is the same as "addrBrk".
*/
addrBrk = pLevel->addrBrk = pLevel->addrNxt = sqlite3VdbeMakeLabel(v);
addrCont = pLevel->addrCont = sqlite3VdbeMakeLabel(v);
/* If this is the right table of a LEFT OUTER JOIN, allocate and
** initialize a memory cell that records if this table matches any
** row of the left table of the join.
*/
if( pLevel->iFrom>0 && (pTabItem[0].jointype & JT_LEFT)!=0 ){
pLevel->iLeftJoin = ++pParse->nMem;
sqlite3VdbeAddOp2(v, OP_Integer, 0, pLevel->iLeftJoin);
VdbeComment((v, "init LEFT JOIN no-match flag"));
}
#ifndef SQLITE_OMIT_VIRTUALTABLE
if( (pLevel->plan.wsFlags & WHERE_VIRTUALTABLE)!=0 ){
/* Case 0: The table is a virtual-table. Use the VFilter and VNext
** to access the data.
*/
int iReg; /* P3 Value for OP_VFilter */
sqlite3_index_info *pVtabIdx = pLevel->plan.u.pVtabIdx;
int nConstraint = pVtabIdx->nConstraint;
struct sqlite3_index_constraint_usage *aUsage =
pVtabIdx->aConstraintUsage;
const struct sqlite3_index_constraint *aConstraint =
pVtabIdx->aConstraint;
sqlite3ExprCachePush(pParse);
iReg = sqlite3GetTempRange(pParse, nConstraint+2);
for(j=1; j<=nConstraint; j++){
for(k=0; k<nConstraint; k++){
if( aUsage[k].argvIndex==j ){
int iTerm = aConstraint[k].iTermOffset;
sqlite3ExprCode(pParse, pWC->a[iTerm].pExpr->pRight, iReg+j+1);
break;
}
}
if( k==nConstraint ) break;
}
sqlite3VdbeAddOp2(v, OP_Integer, pVtabIdx->idxNum, iReg);
sqlite3VdbeAddOp2(v, OP_Integer, j-1, iReg+1);
sqlite3VdbeAddOp4(v, OP_VFilter, iCur, addrBrk, iReg, pVtabIdx->idxStr,
pVtabIdx->needToFreeIdxStr ? P4_MPRINTF : P4_STATIC);
pVtabIdx->needToFreeIdxStr = 0;
for(j=0; j<nConstraint; j++){
if( aUsage[j].omit ){
int iTerm = aConstraint[j].iTermOffset;
disableTerm(pLevel, &pWC->a[iTerm]);
}
}
pLevel->op = OP_VNext;
pLevel->p1 = iCur;
pLevel->p2 = sqlite3VdbeCurrentAddr(v);
sqlite3ReleaseTempRange(pParse, iReg, nConstraint+2);
sqlite3ExprCachePop(pParse, 1);
}else
#endif /* SQLITE_OMIT_VIRTUALTABLE */
if( pLevel->plan.wsFlags & WHERE_ROWID_EQ ){
/* Case 1: We can directly reference a single row using an
** equality comparison against the ROWID field. Or
** we reference multiple rows using a "rowid IN (...)"
** construct.
*/
iReleaseReg = sqlite3GetTempReg(pParse);
pTerm = findTerm(pWC, iCur, -1, notReady, WO_EQ|WO_IN, 0);
assert( pTerm!=0 );
assert( pTerm->pExpr!=0 );
assert( pTerm->leftCursor==iCur );
assert( omitTable==0 );
testcase( pTerm->wtFlags & TERM_VIRTUAL ); /* EV: R-30575-11662 */
iRowidReg = codeEqualityTerm(pParse, pTerm, pLevel, iReleaseReg);
addrNxt = pLevel->addrNxt;
sqlite3VdbeAddOp2(v, OP_MustBeInt, iRowidReg, addrNxt);
sqlite3VdbeAddOp3(v, OP_NotExists, iCur, addrNxt, iRowidReg);
sqlite3ExprCacheStore(pParse, iCur, -1, iRowidReg);
VdbeComment((v, "pk"));
pLevel->op = OP_Noop;
}else if( pLevel->plan.wsFlags & WHERE_ROWID_RANGE ){
/* Case 2: We have an inequality comparison against the ROWID field.
*/
int testOp = OP_Noop;
int start;
int memEndValue = 0;
WhereTerm *pStart, *pEnd;
assert( omitTable==0 );
pStart = findTerm(pWC, iCur, -1, notReady, WO_GT|WO_GE, 0);
pEnd = findTerm(pWC, iCur, -1, notReady, WO_LT|WO_LE, 0);
if( bRev ){
pTerm = pStart;
pStart = pEnd;
pEnd = pTerm;
}
if( pStart ){
Expr *pX; /* The expression that defines the start bound */
int r1, rTemp; /* Registers for holding the start boundary */
/* The following constant maps TK_xx codes into corresponding
** seek opcodes. It depends on a particular ordering of TK_xx
*/
const u8 aMoveOp[] = {
/* TK_GT */ OP_SeekGt,
/* TK_LE */ OP_SeekLe,
/* TK_LT */ OP_SeekLt,
/* TK_GE */ OP_SeekGe
};
assert( TK_LE==TK_GT+1 ); /* Make sure the ordering.. */
assert( TK_LT==TK_GT+2 ); /* ... of the TK_xx values... */
assert( TK_GE==TK_GT+3 ); /* ... is correcct. */
testcase( pStart->wtFlags & TERM_VIRTUAL ); /* EV: R-30575-11662 */
pX = pStart->pExpr;
assert( pX!=0 );
assert( pStart->leftCursor==iCur );
r1 = sqlite3ExprCodeTemp(pParse, pX->pRight, &rTemp);
sqlite3VdbeAddOp3(v, aMoveOp[pX->op-TK_GT], iCur, addrBrk, r1);
VdbeComment((v, "pk"));
sqlite3ExprCacheAffinityChange(pParse, r1, 1);
sqlite3ReleaseTempReg(pParse, rTemp);
disableTerm(pLevel, pStart);
}else{
sqlite3VdbeAddOp2(v, bRev ? OP_Last : OP_Rewind, iCur, addrBrk);
}
if( pEnd ){
Expr *pX;
pX = pEnd->pExpr;
assert( pX!=0 );
assert( pEnd->leftCursor==iCur );
testcase( pEnd->wtFlags & TERM_VIRTUAL ); /* EV: R-30575-11662 */
memEndValue = ++pParse->nMem;
sqlite3ExprCode(pParse, pX->pRight, memEndValue);
if( pX->op==TK_LT || pX->op==TK_GT ){
testOp = bRev ? OP_Le : OP_Ge;
}else{
testOp = bRev ? OP_Lt : OP_Gt;
}
disableTerm(pLevel, pEnd);
}
start = sqlite3VdbeCurrentAddr(v);
pLevel->op = bRev ? OP_Prev : OP_Next;
pLevel->p1 = iCur;
pLevel->p2 = start;
if( pStart==0 && pEnd==0 ){
pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
}else{
assert( pLevel->p5==0 );
}
if( testOp!=OP_Noop ){
iRowidReg = iReleaseReg = sqlite3GetTempReg(pParse);
sqlite3VdbeAddOp2(v, OP_Rowid, iCur, iRowidReg);
sqlite3ExprCacheStore(pParse, iCur, -1, iRowidReg);
sqlite3VdbeAddOp3(v, testOp, memEndValue, addrBrk, iRowidReg);
sqlite3VdbeChangeP5(v, SQLITE_AFF_NUMERIC | SQLITE_JUMPIFNULL);
}
}else if( pLevel->plan.wsFlags & (WHERE_COLUMN_RANGE|WHERE_COLUMN_EQ) ){
/* Case 3: A scan using an index.
**
** The WHERE clause may contain zero or more equality
** terms ("==" or "IN" operators) that refer to the N
** left-most columns of the index. It may also contain
** inequality constraints (>, <, >= or <=) on the indexed
** column that immediately follows the N equalities. Only
** the right-most column can be an inequality - the rest must
** use the "==" and "IN" operators. For example, if the
** index is on (x,y,z), then the following clauses are all
** optimized:
**
** x=5
** x=5 AND y=10
** x=5 AND y<10
** x=5 AND y>5 AND y<10
** x=5 AND y=5 AND z<=10
**
** The z<10 term of the following cannot be used, only
** the x=5 term:
**
** x=5 AND z<10
**
** N may be zero if there are inequality constraints.
** If there are no inequality constraints, then N is at
** least one.
**
** This case is also used when there are no WHERE clause
** constraints but an index is selected anyway, in order
** to force the output order to conform to an ORDER BY.
*/
static const u8 aStartOp[] = {
0,
0,
OP_Rewind, /* 2: (!start_constraints && startEq && !bRev) */
OP_Last, /* 3: (!start_constraints && startEq && bRev) */
OP_SeekGt, /* 4: (start_constraints && !startEq && !bRev) */
OP_SeekLt, /* 5: (start_constraints && !startEq && bRev) */
OP_SeekGe, /* 6: (start_constraints && startEq && !bRev) */
OP_SeekLe /* 7: (start_constraints && startEq && bRev) */
};
static const u8 aEndOp[] = {
OP_Noop, /* 0: (!end_constraints) */
OP_IdxGE, /* 1: (end_constraints && !bRev) */
OP_IdxLT /* 2: (end_constraints && bRev) */
};
int nEq = pLevel->plan.nEq; /* Number of == or IN terms */
int isMinQuery = 0; /* If this is an optimized SELECT min(x).. */
int regBase; /* Base register holding constraint values */
int r1; /* Temp register */
WhereTerm *pRangeStart = 0; /* Inequality constraint at range start */
WhereTerm *pRangeEnd = 0; /* Inequality constraint at range end */
int startEq; /* True if range start uses ==, >= or <= */
int endEq; /* True if range end uses ==, >= or <= */
int start_constraints; /* Start of range is constrained */
int nConstraint; /* Number of constraint terms */
Index *pIdx; /* The index we will be using */
int iIdxCur; /* The VDBE cursor for the index */
int nExtraReg = 0; /* Number of extra registers needed */
int op; /* Instruction opcode */
char *zStartAff; /* Affinity for start of range constraint */
char *zEndAff; /* Affinity for end of range constraint */
pIdx = pLevel->plan.u.pIdx;
iIdxCur = pLevel->iIdxCur;
k = pIdx->aiColumn[nEq]; /* Column for inequality constraints */
/* If this loop satisfies a sort order (pOrderBy) request that
** was passed to this function to implement a "SELECT min(x) ..."
** query, then the caller will only allow the loop to run for
** a single iteration. This means that the first row returned
** should not have a NULL value stored in 'x'. If column 'x' is
** the first one after the nEq equality constraints in the index,
** this requires some special handling.
*/
if( (wctrlFlags&WHERE_ORDERBY_MIN)!=0
&& (pLevel->plan.wsFlags&WHERE_ORDERBY)
&& (pIdx->nColumn>nEq)
){
/* assert( pOrderBy->nExpr==1 ); */
/* assert( pOrderBy->a[0].pExpr->iColumn==pIdx->aiColumn[nEq] ); */
isMinQuery = 1;
nExtraReg = 1;
}
/* Find any inequality constraint terms for the start and end
** of the range.
*/
if( pLevel->plan.wsFlags & WHERE_TOP_LIMIT ){
pRangeEnd = findTerm(pWC, iCur, k, notReady, (WO_LT|WO_LE), pIdx);
nExtraReg = 1;
}
if( pLevel->plan.wsFlags & WHERE_BTM_LIMIT ){
pRangeStart = findTerm(pWC, iCur, k, notReady, (WO_GT|WO_GE), pIdx);
nExtraReg = 1;
}
/* Generate code to evaluate all constraint terms using == or IN
** and store the values of those terms in an array of registers
** starting at regBase.
*/
regBase = codeAllEqualityTerms(
pParse, pLevel, pWC, notReady, nExtraReg, &zStartAff
);
zEndAff = sqlite3DbStrDup(pParse->db, zStartAff);
addrNxt = pLevel->addrNxt;
/* If we are doing a reverse order scan on an ascending index, or
** a forward order scan on a descending index, interchange the
** start and end terms (pRangeStart and pRangeEnd).
*/
if( nEq<pIdx->nColumn && bRev==(pIdx->aSortOrder[nEq]==SQLITE_SO_ASC) ){
SWAP(WhereTerm *, pRangeEnd, pRangeStart);
}
testcase( pRangeStart && pRangeStart->eOperator & WO_LE );
testcase( pRangeStart && pRangeStart->eOperator & WO_GE );
testcase( pRangeEnd && pRangeEnd->eOperator & WO_LE );
testcase( pRangeEnd && pRangeEnd->eOperator & WO_GE );
startEq = !pRangeStart || pRangeStart->eOperator & (WO_LE|WO_GE);
endEq = !pRangeEnd || pRangeEnd->eOperator & (WO_LE|WO_GE);
start_constraints = pRangeStart || nEq>0;
/* Seek the index cursor to the start of the range. */
nConstraint = nEq;
if( pRangeStart ){
Expr *pRight = pRangeStart->pExpr->pRight;
sqlite3ExprCode(pParse, pRight, regBase+nEq);
if( (pRangeStart->wtFlags & TERM_VNULL)==0 ){
sqlite3ExprCodeIsNullJump(v, pRight, regBase+nEq, addrNxt);
}
if( zStartAff ){
if( sqlite3CompareAffinity(pRight, zStartAff[nEq])==SQLITE_AFF_NONE){
/* Since the comparison is to be performed with no conversions
** applied to the operands, set the affinity to apply to pRight to
** SQLITE_AFF_NONE. */
zStartAff[nEq] = SQLITE_AFF_NONE;
}
if( sqlite3ExprNeedsNoAffinityChange(pRight, zStartAff[nEq]) ){
zStartAff[nEq] = SQLITE_AFF_NONE;
}
}
nConstraint++;
testcase( pRangeStart->wtFlags & TERM_VIRTUAL ); /* EV: R-30575-11662 */
}else if( isMinQuery ){
sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
nConstraint++;
startEq = 0;
start_constraints = 1;
}
codeApplyAffinity(pParse, regBase, nConstraint, zStartAff);
op = aStartOp[(start_constraints<<2) + (startEq<<1) + bRev];
assert( op!=0 );
testcase( op==OP_Rewind );
testcase( op==OP_Last );
testcase( op==OP_SeekGt );
testcase( op==OP_SeekGe );
testcase( op==OP_SeekLe );
testcase( op==OP_SeekLt );
sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
/* Load the value for the inequality constraint at the end of the
** range (if any).
*/
nConstraint = nEq;
if( pRangeEnd ){
Expr *pRight = pRangeEnd->pExpr->pRight;
sqlite3ExprCacheRemove(pParse, regBase+nEq, 1);
sqlite3ExprCode(pParse, pRight, regBase+nEq);
if( (pRangeEnd->wtFlags & TERM_VNULL)==0 ){
sqlite3ExprCodeIsNullJump(v, pRight, regBase+nEq, addrNxt);
}
if( zEndAff ){
if( sqlite3CompareAffinity(pRight, zEndAff[nEq])==SQLITE_AFF_NONE){
/* Since the comparison is to be performed with no conversions
** applied to the operands, set the affinity to apply to pRight to
** SQLITE_AFF_NONE. */
zEndAff[nEq] = SQLITE_AFF_NONE;
}
if( sqlite3ExprNeedsNoAffinityChange(pRight, zEndAff[nEq]) ){
zEndAff[nEq] = SQLITE_AFF_NONE;
}
}
codeApplyAffinity(pParse, regBase, nEq+1, zEndAff);
nConstraint++;
testcase( pRangeEnd->wtFlags & TERM_VIRTUAL ); /* EV: R-30575-11662 */
}
sqlite3DbFree(pParse->db, zStartAff);
sqlite3DbFree(pParse->db, zEndAff);
/* Top of the loop body */
pLevel->p2 = sqlite3VdbeCurrentAddr(v);
/* Check if the index cursor is past the end of the range. */
op = aEndOp[(pRangeEnd || nEq) * (1 + bRev)];
testcase( op==OP_Noop );
testcase( op==OP_IdxGE );
testcase( op==OP_IdxLT );
if( op!=OP_Noop ){
sqlite3VdbeAddOp4Int(v, op, iIdxCur, addrNxt, regBase, nConstraint);
sqlite3VdbeChangeP5(v, endEq!=bRev ?1:0);
}
/* If there are inequality constraints, check that the value
** of the table column that the inequality contrains is not NULL.
** If it is, jump to the next iteration of the loop.
*/
r1 = sqlite3GetTempReg(pParse);
testcase( pLevel->plan.wsFlags & WHERE_BTM_LIMIT );
testcase( pLevel->plan.wsFlags & WHERE_TOP_LIMIT );
if( (pLevel->plan.wsFlags & (WHERE_BTM_LIMIT|WHERE_TOP_LIMIT))!=0 ){
sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, nEq, r1);
sqlite3VdbeAddOp2(v, OP_IsNull, r1, addrCont);
}
sqlite3ReleaseTempReg(pParse, r1);
/* Seek the table cursor, if required */
disableTerm(pLevel, pRangeStart);
disableTerm(pLevel, pRangeEnd);
if( !omitTable ){
iRowidReg = iReleaseReg = sqlite3GetTempReg(pParse);
sqlite3VdbeAddOp2(v, OP_IdxRowid, iIdxCur, iRowidReg);
sqlite3ExprCacheStore(pParse, iCur, -1, iRowidReg);
sqlite3VdbeAddOp2(v, OP_Seek, iCur, iRowidReg); /* Deferred seek */
}
/* Record the instruction used to terminate the loop. Disable
** WHERE clause terms made redundant by the index range scan.
*/
if( pLevel->plan.wsFlags & WHERE_UNIQUE ){
pLevel->op = OP_Noop;
}else if( bRev ){
pLevel->op = OP_Prev;
}else{
pLevel->op = OP_Next;
}
pLevel->p1 = iIdxCur;
}else
#ifndef SQLITE_OMIT_OR_OPTIMIZATION
if( pLevel->plan.wsFlags & WHERE_MULTI_OR ){
/* Case 4: Two or more separately indexed terms connected by OR
**
** Example:
**
** CREATE TABLE t1(a,b,c,d);
** CREATE INDEX i1 ON t1(a);
** CREATE INDEX i2 ON t1(b);
** CREATE INDEX i3 ON t1(c);
**
** SELECT * FROM t1 WHERE a=5 OR b=7 OR (c=11 AND d=13)
**
** In the example, there are three indexed terms connected by OR.
** The top of the loop looks like this:
**
** Null 1 # Zero the rowset in reg 1
**
** Then, for each indexed term, the following. The arguments to
** RowSetTest are such that the rowid of the current row is inserted
** into the RowSet. If it is already present, control skips the
** Gosub opcode and jumps straight to the code generated by WhereEnd().
**
** sqlite3WhereBegin(<term>)
** RowSetTest # Insert rowid into rowset
** Gosub 2 A
** sqlite3WhereEnd()
**
** Following the above, code to terminate the loop. Label A, the target
** of the Gosub above, jumps to the instruction right after the Goto.
**
** Null 1 # Zero the rowset in reg 1
** Goto B # The loop is finished.
**
** A: <loop body> # Return data, whatever.
**
** Return 2 # Jump back to the Gosub
**
** B: <after the loop>
**
*/
WhereClause *pOrWc; /* The OR-clause broken out into subterms */
SrcList *pOrTab; /* Shortened table list or OR-clause generation */
int regReturn = ++pParse->nMem; /* Register used with OP_Gosub */
int regRowset = 0; /* Register for RowSet object */
int regRowid = 0; /* Register holding rowid */
int iLoopBody = sqlite3VdbeMakeLabel(v); /* Start of loop body */
int iRetInit; /* Address of regReturn init */
int untestedTerms = 0; /* Some terms not completely tested */
int ii;
pTerm = pLevel->plan.u.pTerm;
assert( pTerm!=0 );
assert( pTerm->eOperator==WO_OR );
assert( (pTerm->wtFlags & TERM_ORINFO)!=0 );
pOrWc = &pTerm->u.pOrInfo->wc;
pLevel->op = OP_Return;
pLevel->p1 = regReturn;
/* Set up a new SrcList ni pOrTab containing the table being scanned
** by this loop in the a[0] slot and all notReady tables in a[1..] slots.
** This becomes the SrcList in the recursive call to sqlite3WhereBegin().
*/
if( pWInfo->nLevel>1 ){
int nNotReady; /* The number of notReady tables */
struct SrcList_item *origSrc; /* Original list of tables */
nNotReady = pWInfo->nLevel - iLevel - 1;
pOrTab = sqlite3StackAllocRaw(pParse->db,
sizeof(*pOrTab)+ nNotReady*sizeof(pOrTab->a[0]));
if( pOrTab==0 ) return notReady;
pOrTab->nAlloc = (i16)(nNotReady + 1);
pOrTab->nSrc = pOrTab->nAlloc;
memcpy(pOrTab->a, pTabItem, sizeof(*pTabItem));
origSrc = pWInfo->pTabList->a;
for(k=1; k<=nNotReady; k++){
memcpy(&pOrTab->a[k], &origSrc[pLevel[k].iFrom], sizeof(pOrTab->a[k]));
}
}else{
pOrTab = pWInfo->pTabList;
}
/* Initialize the rowset register to contain NULL. An SQL NULL is
** equivalent to an empty rowset.
**
** Also initialize regReturn to contain the address of the instruction
** immediately following the OP_Return at the bottom of the loop. This
** is required in a few obscure LEFT JOIN cases where control jumps
** over the top of the loop into the body of it. In this case the
** correct response for the end-of-loop code (the OP_Return) is to
** fall through to the next instruction, just as an OP_Next does if
** called on an uninitialized cursor.
*/
if( (wctrlFlags & WHERE_DUPLICATES_OK)==0 ){
regRowset = ++pParse->nMem;
regRowid = ++pParse->nMem;
sqlite3VdbeAddOp2(v, OP_Null, 0, regRowset);
}
iRetInit = sqlite3VdbeAddOp2(v, OP_Integer, 0, regReturn);
for(ii=0; ii<pOrWc->nTerm; ii++){
WhereTerm *pOrTerm = &pOrWc->a[ii];
if( pOrTerm->leftCursor==iCur || pOrTerm->eOperator==WO_AND ){
WhereInfo *pSubWInfo; /* Info for single OR-term scan */
/* Loop through table entries that match term pOrTerm. */
pSubWInfo = sqlite3WhereBegin(pParse, pOrTab, pOrTerm->pExpr, 0,
WHERE_OMIT_OPEN | WHERE_OMIT_CLOSE |
WHERE_FORCE_TABLE | WHERE_ONETABLE_ONLY);
if( pSubWInfo ){
explainOneScan(
pParse, pOrTab, &pSubWInfo->a[0], iLevel, pLevel->iFrom, 0
);
if( (wctrlFlags & WHERE_DUPLICATES_OK)==0 ){
int iSet = ((ii==pOrWc->nTerm-1)?-1:ii);
int r;
r = sqlite3ExprCodeGetColumn(pParse, pTabItem->pTab, -1, iCur,
regRowid);
sqlite3VdbeAddOp4Int(v, OP_RowSetTest, regRowset,
sqlite3VdbeCurrentAddr(v)+2, r, iSet);
}
sqlite3VdbeAddOp2(v, OP_Gosub, regReturn, iLoopBody);
/* The pSubWInfo->untestedTerms flag means that this OR term
** contained one or more AND term from a notReady table. The
** terms from the notReady table could not be tested and will
** need to be tested later.
*/
if( pSubWInfo->untestedTerms ) untestedTerms = 1;
/* Finish the loop through table entries that match term pOrTerm. */
sqlite3WhereEnd(pSubWInfo);
}
}
}
sqlite3VdbeChangeP1(v, iRetInit, sqlite3VdbeCurrentAddr(v));
sqlite3VdbeAddOp2(v, OP_Goto, 0, pLevel->addrBrk);
sqlite3VdbeResolveLabel(v, iLoopBody);
if( pWInfo->nLevel>1 ) sqlite3StackFree(pParse->db, pOrTab);
if( !untestedTerms ) disableTerm(pLevel, pTerm);
}else
#endif /* SQLITE_OMIT_OR_OPTIMIZATION */
{
/* Case 5: There is no usable index. We must do a complete
** scan of the entire table.
*/
static const u8 aStep[] = { OP_Next, OP_Prev };
static const u8 aStart[] = { OP_Rewind, OP_Last };
assert( bRev==0 || bRev==1 );
assert( omitTable==0 );
pLevel->op = aStep[bRev];
pLevel->p1 = iCur;
pLevel->p2 = 1 + sqlite3VdbeAddOp2(v, aStart[bRev], iCur, addrBrk);
pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
}
notReady &= ~getMask(pWC->pMaskSet, iCur);
/* Insert code to test every subexpression that can be completely
** computed using the current set of tables.
**
** IMPLEMENTATION-OF: R-49525-50935 Terms that cannot be satisfied through
** the use of indices become tests that are evaluated against each row of
** the relevant input tables.
*/
for(pTerm=pWC->a, j=pWC->nTerm; j>0; j--, pTerm++){
Expr *pE;
testcase( pTerm->wtFlags & TERM_VIRTUAL ); /* IMP: R-30575-11662 */
testcase( pTerm->wtFlags & TERM_CODED );
if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
if( (pTerm->prereqAll & notReady)!=0 ){
testcase( pWInfo->untestedTerms==0
&& (pWInfo->wctrlFlags & WHERE_ONETABLE_ONLY)!=0 );
pWInfo->untestedTerms = 1;
continue;
}
pE = pTerm->pExpr;
assert( pE!=0 );
if( pLevel->iLeftJoin && !ExprHasProperty(pE, EP_FromJoin) ){
continue;
}
sqlite3ExprIfFalse(pParse, pE, addrCont, SQLITE_JUMPIFNULL);
pTerm->wtFlags |= TERM_CODED;
}
/* For a LEFT OUTER JOIN, generate code that will record the fact that
** at least one row of the right table has matched the left table.
*/
if( pLevel->iLeftJoin ){
pLevel->addrFirst = sqlite3VdbeCurrentAddr(v);
sqlite3VdbeAddOp2(v, OP_Integer, 1, pLevel->iLeftJoin);
VdbeComment((v, "record LEFT JOIN hit"));
sqlite3ExprCacheClear(pParse);
for(pTerm=pWC->a, j=0; j<pWC->nTerm; j++, pTerm++){
testcase( pTerm->wtFlags & TERM_VIRTUAL ); /* IMP: R-30575-11662 */
testcase( pTerm->wtFlags & TERM_CODED );
if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
if( (pTerm->prereqAll & notReady)!=0 ){
assert( pWInfo->untestedTerms );
continue;
}
assert( pTerm->pExpr );
sqlite3ExprIfFalse(pParse, pTerm->pExpr, addrCont, SQLITE_JUMPIFNULL);
pTerm->wtFlags |= TERM_CODED;
}
}
sqlite3ReleaseTempReg(pParse, iReleaseReg);
return notReady;
}
#if defined(SQLITE_TEST)
/*
** The following variable holds a text description of query plan generated
** by the most recent call to sqlite3WhereBegin(). Each call to WhereBegin
** overwrites the previous. This information is used for testing and
** analysis only.
*/
char sqlite3_query_plan[BMS*2*40]; /* Text of the join */
static int nQPlan = 0; /* Next free slow in _query_plan[] */
#endif /* SQLITE_TEST */
/*
** Free a WhereInfo structure
*/
static void whereInfoFree(sqlite3 *db, WhereInfo *pWInfo){
if( ALWAYS(pWInfo) ){
int i;
for(i=0; i<pWInfo->nLevel; i++){
sqlite3_index_info *pInfo = pWInfo->a[i].pIdxInfo;
if( pInfo ){
/* assert( pInfo->needToFreeIdxStr==0 || db->mallocFailed ); */
if( pInfo->needToFreeIdxStr ){
sqlite3_free(pInfo->idxStr);
}
sqlite3DbFree(db, pInfo);
}
if( pWInfo->a[i].plan.wsFlags & WHERE_TEMP_INDEX ){
Index *pIdx = pWInfo->a[i].plan.u.pIdx;
if( pIdx ){
sqlite3DbFree(db, pIdx->zColAff);
sqlite3DbFree(db, pIdx);
}
}
}
whereClauseClear(pWInfo->pWC);
sqlite3DbFree(db, pWInfo);
}
}
/*
** Generate the beginning of the loop used for WHERE clause processing.
** The return value is a pointer to an opaque structure that contains
** information needed to terminate the loop. Later, the calling routine
** should invoke sqlite3WhereEnd() with the return value of this function
** in order to complete the WHERE clause processing.
**
** If an error occurs, this routine returns NULL.
**
** The basic idea is to do a nested loop, one loop for each table in
** the FROM clause of a select. (INSERT and UPDATE statements are the
** same as a SELECT with only a single table in the FROM clause.) For
** example, if the SQL is this:
**
** SELECT * FROM t1, t2, t3 WHERE ...;
**
** Then the code generated is conceptually like the following:
**
** foreach row1 in t1 do \ Code generated
** foreach row2 in t2 do |-- by sqlite3WhereBegin()
** foreach row3 in t3 do /
** ...
** end \ Code generated
** end |-- by sqlite3WhereEnd()
** end /
**
** Note that the loops might not be nested in the order in which they
** appear in the FROM clause if a different order is better able to make
** use of indices. Note also that when the IN operator appears in
** the WHERE clause, it might result in additional nested loops for
** scanning through all values on the right-hand side of the IN.
**
** There are Btree cursors associated with each table. t1 uses cursor
** number pTabList->a[0].iCursor. t2 uses the cursor pTabList->a[1].iCursor.
** And so forth. This routine generates code to open those VDBE cursors
** and sqlite3WhereEnd() generates the code to close them.
**
** The code that sqlite3WhereBegin() generates leaves the cursors named
** in pTabList pointing at their appropriate entries. The [...] code
** can use OP_Column and OP_Rowid opcodes on these cursors to extract
** data from the various tables of the loop.
**
** If the WHERE clause is empty, the foreach loops must each scan their
** entire tables. Thus a three-way join is an O(N^3) operation. But if
** the tables have indices and there are terms in the WHERE clause that
** refer to those indices, a complete table scan can be avoided and the
** code will run much faster. Most of the work of this routine is checking
** to see if there are indices that can be used to speed up the loop.
**
** Terms of the WHERE clause are also used to limit which rows actually
** make it to the "..." in the middle of the loop. After each "foreach",
** terms of the WHERE clause that use only terms in that loop and outer
** loops are evaluated and if false a jump is made around all subsequent
** inner loops (or around the "..." if the test occurs within the inner-
** most loop)
**
** OUTER JOINS
**
** An outer join of tables t1 and t2 is conceptally coded as follows:
**
** foreach row1 in t1 do
** flag = 0
** foreach row2 in t2 do
** start:
** ...
** flag = 1
** end
** if flag==0 then
** move the row2 cursor to a null row
** goto start
** fi
** end
**
** ORDER BY CLAUSE PROCESSING
**
** *ppOrderBy is a pointer to the ORDER BY clause of a SELECT statement,
** if there is one. If there is no ORDER BY clause or if this routine
** is called from an UPDATE or DELETE statement, then ppOrderBy is NULL.
**
** If an index can be used so that the natural output order of the table
** scan is correct for the ORDER BY clause, then that index is used and
** *ppOrderBy is set to NULL. This is an optimization that prevents an
** unnecessary sort of the result set if an index appropriate for the
** ORDER BY clause already exists.
**
** If the where clause loops cannot be arranged to provide the correct
** output order, then the *ppOrderBy is unchanged.
*/
WhereInfo *sqlite3WhereBegin(
Parse *pParse, /* The parser context */
SrcList *pTabList, /* A list of all tables to be scanned */
Expr *pWhere, /* The WHERE clause */
ExprList **ppOrderBy, /* An ORDER BY clause, or NULL */
u16 wctrlFlags /* One of the WHERE_* flags defined in sqliteInt.h */
){
int i; /* Loop counter */
int nByteWInfo; /* Num. bytes allocated for WhereInfo struct */
int nTabList; /* Number of elements in pTabList */
WhereInfo *pWInfo; /* Will become the return value of this function */
Vdbe *v = pParse->pVdbe; /* The virtual database engine */
Bitmask notReady; /* Cursors that are not yet positioned */
WhereMaskSet *pMaskSet; /* The expression mask set */
WhereClause *pWC; /* Decomposition of the WHERE clause */
struct SrcList_item *pTabItem; /* A single entry from pTabList */
WhereLevel *pLevel; /* A single level in the pWInfo list */
int iFrom; /* First unused FROM clause element */
int andFlags; /* AND-ed combination of all pWC->a[].wtFlags */
sqlite3 *db; /* Database connection */
/* The number of tables in the FROM clause is limited by the number of
** bits in a Bitmask
*/
testcase( pTabList->nSrc==BMS );
if( pTabList->nSrc>BMS ){
sqlite3ErrorMsg(pParse, "at most %d tables in a join", BMS);
return 0;
}
/* This function normally generates a nested loop for all tables in
** pTabList. But if the WHERE_ONETABLE_ONLY flag is set, then we should
** only generate code for the first table in pTabList and assume that
** any cursors associated with subsequent tables are uninitialized.
*/
nTabList = (wctrlFlags & WHERE_ONETABLE_ONLY) ? 1 : pTabList->nSrc;
/* Allocate and initialize the WhereInfo structure that will become the
** return value. A single allocation is used to store the WhereInfo
** struct, the contents of WhereInfo.a[], the WhereClause structure
** and the WhereMaskSet structure. Since WhereClause contains an 8-byte
** field (type Bitmask) it must be aligned on an 8-byte boundary on
** some architectures. Hence the ROUND8() below.
*/
db = pParse->db;
nByteWInfo = ROUND8(sizeof(WhereInfo)+(nTabList-1)*sizeof(WhereLevel));
pWInfo = sqlite3DbMallocZero(db,
nByteWInfo +
sizeof(WhereClause) +
sizeof(WhereMaskSet)
);
if( db->mallocFailed ){
sqlite3DbFree(db, pWInfo);
pWInfo = 0;
goto whereBeginError;
}
pWInfo->nLevel = nTabList;
pWInfo->pParse = pParse;
pWInfo->pTabList = pTabList;
pWInfo->iBreak = sqlite3VdbeMakeLabel(v);
pWInfo->pWC = pWC = (WhereClause *)&((u8 *)pWInfo)[nByteWInfo];
pWInfo->wctrlFlags = wctrlFlags;
pWInfo->savedNQueryLoop = pParse->nQueryLoop;
pMaskSet = (WhereMaskSet*)&pWC[1];
/* Split the WHERE clause into separate subexpressions where each
** subexpression is separated by an AND operator.
*/
initMaskSet(pMaskSet);
whereClauseInit(pWC, pParse, pMaskSet);
sqlite3ExprCodeConstants(pParse, pWhere);
whereSplit(pWC, pWhere, TK_AND); /* IMP: R-15842-53296 */
/* Special case: a WHERE clause that is constant. Evaluate the
** expression and either jump over all of the code or fall thru.
*/
if( pWhere && (nTabList==0 || sqlite3ExprIsConstantNotJoin(pWhere)) ){
sqlite3ExprIfFalse(pParse, pWhere, pWInfo->iBreak, SQLITE_JUMPIFNULL);
pWhere = 0;
}
/* Assign a bit from the bitmask to every term in the FROM clause.
**
** When assigning bitmask values to FROM clause cursors, it must be
** the case that if X is the bitmask for the N-th FROM clause term then
** the bitmask for all FROM clause terms to the left of the N-th term
** is (X-1). An expression from the ON clause of a LEFT JOIN can use
** its Expr.iRightJoinTable value to find the bitmask of the right table
** of the join. Subtracting one from the right table bitmask gives a
** bitmask for all tables to the left of the join. Knowing the bitmask
** for all tables to the left of a left join is important. Ticket #3015.
**
** Configure the WhereClause.vmask variable so that bits that correspond
** to virtual table cursors are set. This is used to selectively disable
** the OR-to-IN transformation in exprAnalyzeOrTerm(). It is not helpful
** with virtual tables.
**
** Note that bitmasks are created for all pTabList->nSrc tables in
** pTabList, not just the first nTabList tables. nTabList is normally
** equal to pTabList->nSrc but might be shortened to 1 if the
** WHERE_ONETABLE_ONLY flag is set.
*/
assert( pWC->vmask==0 && pMaskSet->n==0 );
for(i=0; i<pTabList->nSrc; i++){
createMask(pMaskSet, pTabList->a[i].iCursor);
#ifndef SQLITE_OMIT_VIRTUALTABLE
if( ALWAYS(pTabList->a[i].pTab) && IsVirtual(pTabList->a[i].pTab) ){
pWC->vmask |= ((Bitmask)1 << i);
}
#endif
}
#ifndef NDEBUG
{
Bitmask toTheLeft = 0;
for(i=0; i<pTabList->nSrc; i++){
Bitmask m = getMask(pMaskSet, pTabList->a[i].iCursor);
assert( (m-1)==toTheLeft );
toTheLeft |= m;
}
}
#endif
/* Analyze all of the subexpressions. Note that exprAnalyze() might
** add new virtual terms onto the end of the WHERE clause. We do not
** want to analyze these virtual terms, so start analyzing at the end
** and work forward so that the added virtual terms are never processed.
*/
exprAnalyzeAll(pTabList, pWC);
if( db->mallocFailed ){
goto whereBeginError;
}
/* Chose the best index to use for each table in the FROM clause.
**
** This loop fills in the following fields:
**
** pWInfo->a[].pIdx The index to use for this level of the loop.
** pWInfo->a[].wsFlags WHERE_xxx flags associated with pIdx
** pWInfo->a[].nEq The number of == and IN constraints
** pWInfo->a[].iFrom Which term of the FROM clause is being coded
** pWInfo->a[].iTabCur The VDBE cursor for the database table
** pWInfo->a[].iIdxCur The VDBE cursor for the index
** pWInfo->a[].pTerm When wsFlags==WO_OR, the OR-clause term
**
** This loop also figures out the nesting order of tables in the FROM
** clause.
*/
notReady = ~(Bitmask)0;
andFlags = ~0;
WHERETRACE(("*** Optimizer Start ***\n"));
for(i=iFrom=0, pLevel=pWInfo->a; i<nTabList; i++, pLevel++){
WhereCost bestPlan; /* Most efficient plan seen so far */
Index *pIdx; /* Index for FROM table at pTabItem */
int j; /* For looping over FROM tables */
int bestJ = -1; /* The value of j */
Bitmask m; /* Bitmask value for j or bestJ */
int isOptimal; /* Iterator for optimal/non-optimal search */
int nUnconstrained; /* Number tables without INDEXED BY */
Bitmask notIndexed; /* Mask of tables that cannot use an index */
memset(&bestPlan, 0, sizeof(bestPlan));
bestPlan.rCost = SQLITE_BIG_DBL;
WHERETRACE(("*** Begin search for loop %d ***\n", i));
/* Loop through the remaining entries in the FROM clause to find the
** next nested loop. The loop tests all FROM clause entries
** either once or twice.
**
** The first test is always performed if there are two or more entries
** remaining and never performed if there is only one FROM clause entry
** to choose from. The first test looks for an "optimal" scan. In
** this context an optimal scan is one that uses the same strategy
** for the given FROM clause entry as would be selected if the entry
** were used as the innermost nested loop. In other words, a table
** is chosen such that the cost of running that table cannot be reduced
** by waiting for other tables to run first. This "optimal" test works
** by first assuming that the FROM clause is on the inner loop and finding
** its query plan, then checking to see if that query plan uses any
** other FROM clause terms that are notReady. If no notReady terms are
** used then the "optimal" query plan works.
**
** Note that the WhereCost.nRow parameter for an optimal scan might
** not be as small as it would be if the table really were the innermost
** join. The nRow value can be reduced by WHERE clause constraints
** that do not use indices. But this nRow reduction only happens if the
** table really is the innermost join.
**
** The second loop iteration is only performed if no optimal scan
** strategies were found by the first iteration. This second iteration
** is used to search for the lowest cost scan overall.
**
** Previous versions of SQLite performed only the second iteration -
** the next outermost loop was always that with the lowest overall
** cost. However, this meant that SQLite could select the wrong plan
** for scripts such as the following:
**
** CREATE TABLE t1(a, b);
** CREATE TABLE t2(c, d);
** SELECT * FROM t2, t1 WHERE t2.rowid = t1.a;
**
** The best strategy is to iterate through table t1 first. However it
** is not possible to determine this with a simple greedy algorithm.
** Since the cost of a linear scan through table t2 is the same
** as the cost of a linear scan through table t1, a simple greedy
** algorithm may choose to use t2 for the outer loop, which is a much
** costlier approach.
*/
nUnconstrained = 0;
notIndexed = 0;
for(isOptimal=(iFrom<nTabList-1); isOptimal>=0 && bestJ<0; isOptimal--){
Bitmask mask; /* Mask of tables not yet ready */
for(j=iFrom, pTabItem=&pTabList->a[j]; j<nTabList; j++, pTabItem++){
int doNotReorder; /* True if this table should not be reordered */
WhereCost sCost; /* Cost information from best[Virtual]Index() */
ExprList *pOrderBy; /* ORDER BY clause for index to optimize */
doNotReorder = (pTabItem->jointype & (JT_LEFT|JT_CROSS))!=0;
if( j!=iFrom && doNotReorder ) break;
m = getMask(pMaskSet, pTabItem->iCursor);
if( (m & notReady)==0 ){
if( j==iFrom ) iFrom++;
continue;
}
mask = (isOptimal ? m : notReady);
pOrderBy = ((i==0 && ppOrderBy )?*ppOrderBy:0);
if( pTabItem->pIndex==0 ) nUnconstrained++;
WHERETRACE(("=== trying table %d with isOptimal=%d ===\n",
j, isOptimal));
assert( pTabItem->pTab );
#ifndef SQLITE_OMIT_VIRTUALTABLE
if( IsVirtual(pTabItem->pTab) ){
sqlite3_index_info **pp = &pWInfo->a[j].pIdxInfo;
bestVirtualIndex(pParse, pWC, pTabItem, mask, notReady, pOrderBy,
&sCost, pp);
}else
#endif
{
bestBtreeIndex(pParse, pWC, pTabItem, mask, notReady, pOrderBy,
&sCost);
}
assert( isOptimal || (sCost.used&notReady)==0 );
/* If an INDEXED BY clause is present, then the plan must use that
** index if it uses any index at all */
assert( pTabItem->pIndex==0
|| (sCost.plan.wsFlags & WHERE_NOT_FULLSCAN)==0
|| sCost.plan.u.pIdx==pTabItem->pIndex );
if( isOptimal && (sCost.plan.wsFlags & WHERE_NOT_FULLSCAN)==0 ){
notIndexed |= m;
}
/* Conditions under which this table becomes the best so far:
**
** (1) The table must not depend on other tables that have not
** yet run.
**
** (2) A full-table-scan plan cannot supercede indexed plan unless
** the full-table-scan is an "optimal" plan as defined above.
**
** (3) All tables have an INDEXED BY clause or this table lacks an
** INDEXED BY clause or this table uses the specific
** index specified by its INDEXED BY clause. This rule ensures
** that a best-so-far is always selected even if an impossible
** combination of INDEXED BY clauses are given. The error
** will be detected and relayed back to the application later.
** The NEVER() comes about because rule (2) above prevents
** An indexable full-table-scan from reaching rule (3).
**
** (4) The plan cost must be lower than prior plans or else the
** cost must be the same and the number of rows must be lower.
*/
if( (sCost.used&notReady)==0 /* (1) */
&& (bestJ<0 || (notIndexed&m)!=0 /* (2) */
|| (bestPlan.plan.wsFlags & WHERE_NOT_FULLSCAN)==0
|| (sCost.plan.wsFlags & WHERE_NOT_FULLSCAN)!=0)
&& (nUnconstrained==0 || pTabItem->pIndex==0 /* (3) */
|| NEVER((sCost.plan.wsFlags & WHERE_NOT_FULLSCAN)!=0))
&& (bestJ<0 || sCost.rCost<bestPlan.rCost /* (4) */
|| (sCost.rCost<=bestPlan.rCost
&& sCost.plan.nRow<bestPlan.plan.nRow))
){
WHERETRACE(("=== table %d is best so far"
" with cost=%g and nRow=%g\n",
j, sCost.rCost, sCost.plan.nRow));
bestPlan = sCost;
bestJ = j;
}
if( doNotReorder ) break;
}
}
assert( bestJ>=0 );
assert( notReady & getMask(pMaskSet, pTabList->a[bestJ].iCursor) );
WHERETRACE(("*** Optimizer selects table %d for loop %d"
" with cost=%g and nRow=%g\n",
bestJ, pLevel-pWInfo->a, bestPlan.rCost, bestPlan.plan.nRow));
if( (bestPlan.plan.wsFlags & WHERE_ORDERBY)!=0 ){
*ppOrderBy = 0;
}
andFlags &= bestPlan.plan.wsFlags;
pLevel->plan = bestPlan.plan;
testcase( bestPlan.plan.wsFlags & WHERE_INDEXED );
testcase( bestPlan.plan.wsFlags & WHERE_TEMP_INDEX );
if( bestPlan.plan.wsFlags & (WHERE_INDEXED|WHERE_TEMP_INDEX) ){
pLevel->iIdxCur = pParse->nTab++;
}else{
pLevel->iIdxCur = -1;
}
notReady &= ~getMask(pMaskSet, pTabList->a[bestJ].iCursor);
pLevel->iFrom = (u8)bestJ;
if( bestPlan.plan.nRow>=(double)1 ){
pParse->nQueryLoop *= bestPlan.plan.nRow;
}
/* Check that if the table scanned by this loop iteration had an
** INDEXED BY clause attached to it, that the named index is being
** used for the scan. If not, then query compilation has failed.
** Return an error.
*/
pIdx = pTabList->a[bestJ].pIndex;
if( pIdx ){
if( (bestPlan.plan.wsFlags & WHERE_INDEXED)==0 ){
sqlite3ErrorMsg(pParse, "cannot use index: %s", pIdx->zName);
goto whereBeginError;
}else{
/* If an INDEXED BY clause is used, the bestIndex() function is
** guaranteed to find the index specified in the INDEXED BY clause
** if it find an index at all. */
assert( bestPlan.plan.u.pIdx==pIdx );
}
}
}
WHERETRACE(("*** Optimizer Finished ***\n"));
if( pParse->nErr || db->mallocFailed ){
goto whereBeginError;
}
/* If the total query only selects a single row, then the ORDER BY
** clause is irrelevant.
*/
if( (andFlags & WHERE_UNIQUE)!=0 && ppOrderBy ){
*ppOrderBy = 0;
}
/* If the caller is an UPDATE or DELETE statement that is requesting
** to use a one-pass algorithm, determine if this is appropriate.
** The one-pass algorithm only works if the WHERE clause constraints
** the statement to update a single row.
*/
assert( (wctrlFlags & WHERE_ONEPASS_DESIRED)==0 || pWInfo->nLevel==1 );
if( (wctrlFlags & WHERE_ONEPASS_DESIRED)!=0 && (andFlags & WHERE_UNIQUE)!=0 ){
pWInfo->okOnePass = 1;
pWInfo->a[0].plan.wsFlags &= ~WHERE_IDX_ONLY;
}
/* Open all tables in the pTabList and any indices selected for
** searching those tables.
*/
sqlite3CodeVerifySchema(pParse, -1); /* Insert the cookie verifier Goto */
notReady = ~(Bitmask)0;
pWInfo->nRowOut = (double)1;
for(i=0, pLevel=pWInfo->a; i<nTabList; i++, pLevel++){
Table *pTab; /* Table to open */
int iDb; /* Index of database containing table/index */
pTabItem = &pTabList->a[pLevel->iFrom];
pTab = pTabItem->pTab;
pLevel->iTabCur = pTabItem->iCursor;
pWInfo->nRowOut *= pLevel->plan.nRow;
iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
if( (pTab->tabFlags & TF_Ephemeral)!=0 || pTab->pSelect ){
/* Do nothing */
}else
#ifndef SQLITE_OMIT_VIRTUALTABLE
if( (pLevel->plan.wsFlags & WHERE_VIRTUALTABLE)!=0 ){
const char *pVTab = (const char *)sqlite3GetVTable(db, pTab);
int iCur = pTabItem->iCursor;
sqlite3VdbeAddOp4(v, OP_VOpen, iCur, 0, 0, pVTab, P4_VTAB);
}else
#endif
if( (pLevel->plan.wsFlags & WHERE_IDX_ONLY)==0
&& (wctrlFlags & WHERE_OMIT_OPEN)==0 ){
int op = pWInfo->okOnePass ? OP_OpenWrite : OP_OpenRead;
sqlite3OpenTable(pParse, pTabItem->iCursor, iDb, pTab, op);
testcase( pTab->nCol==BMS-1 );
testcase( pTab->nCol==BMS );
if( !pWInfo->okOnePass && pTab->nCol<BMS ){
Bitmask b = pTabItem->colUsed;
int n = 0;
for(; b; b=b>>1, n++){}
sqlite3VdbeChangeP4(v, sqlite3VdbeCurrentAddr(v)-1,
SQLITE_INT_TO_PTR(n), P4_INT32);
assert( n<=pTab->nCol );
}
}else{
sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
}
#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
if( (pLevel->plan.wsFlags & WHERE_TEMP_INDEX)!=0 ){
constructAutomaticIndex(pParse, pWC, pTabItem, notReady, pLevel);
}else
#endif
if( (pLevel->plan.wsFlags & WHERE_INDEXED)!=0 ){
Index *pIx = pLevel->plan.u.pIdx;
KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIx);
int iIdxCur = pLevel->iIdxCur;
assert( pIx->pSchema==pTab->pSchema );
assert( iIdxCur>=0 );
sqlite3VdbeAddOp4(v, OP_OpenRead, iIdxCur, pIx->tnum, iDb,
(char*)pKey, P4_KEYINFO_HANDOFF);
VdbeComment((v, "%s", pIx->zName));
}
sqlite3CodeVerifySchema(pParse, iDb);
notReady &= ~getMask(pWC->pMaskSet, pTabItem->iCursor);
}
pWInfo->iTop = sqlite3VdbeCurrentAddr(v);
if( db->mallocFailed ) goto whereBeginError;
/* Generate the code to do the search. Each iteration of the for
** loop below generates code for a single nested loop of the VM
** program.
*/
notReady = ~(Bitmask)0;
for(i=0; i<nTabList; i++){
pLevel = &pWInfo->a[i];
explainOneScan(pParse, pTabList, pLevel, i, pLevel->iFrom, wctrlFlags);
notReady = codeOneLoopStart(pWInfo, i, wctrlFlags, notReady);
pWInfo->iContinue = pLevel->addrCont;
}
#ifdef SQLITE_TEST /* For testing and debugging use only */
/* Record in the query plan information about the current table
** and the index used to access it (if any). If the table itself
** is not used, its name is just '{}'. If no index is used
** the index is listed as "{}". If the primary key is used the
** index name is '*'.
*/
for(i=0; i<nTabList; i++){
char *z;
int n;
pLevel = &pWInfo->a[i];
pTabItem = &pTabList->a[pLevel->iFrom];
z = pTabItem->zAlias;
if( z==0 ) z = pTabItem->pTab->zName;
n = sqlite3Strlen30(z);
if( n+nQPlan < sizeof(sqlite3_query_plan)-10 ){
if( pLevel->plan.wsFlags & WHERE_IDX_ONLY ){
memcpy(&sqlite3_query_plan[nQPlan], "{}", 2);
nQPlan += 2;
}else{
memcpy(&sqlite3_query_plan[nQPlan], z, n);
nQPlan += n;
}
sqlite3_query_plan[nQPlan++] = ' ';
}
testcase( pLevel->plan.wsFlags & WHERE_ROWID_EQ );
testcase( pLevel->plan.wsFlags & WHERE_ROWID_RANGE );
if( pLevel->plan.wsFlags & (WHERE_ROWID_EQ|WHERE_ROWID_RANGE) ){
memcpy(&sqlite3_query_plan[nQPlan], "* ", 2);
nQPlan += 2;
}else if( (pLevel->plan.wsFlags & WHERE_INDEXED)!=0 ){
n = sqlite3Strlen30(pLevel->plan.u.pIdx->zName);
if( n+nQPlan < sizeof(sqlite3_query_plan)-2 ){
memcpy(&sqlite3_query_plan[nQPlan], pLevel->plan.u.pIdx->zName, n);
nQPlan += n;
sqlite3_query_plan[nQPlan++] = ' ';
}
}else{
memcpy(&sqlite3_query_plan[nQPlan], "{} ", 3);
nQPlan += 3;
}
}
while( nQPlan>0 && sqlite3_query_plan[nQPlan-1]==' ' ){
sqlite3_query_plan[--nQPlan] = 0;
}
sqlite3_query_plan[nQPlan] = 0;
nQPlan = 0;
#endif /* SQLITE_TEST // Testing and debugging use only */
/* Record the continuation address in the WhereInfo structure. Then
** clean up and return.
*/
return pWInfo;
/* Jump here if malloc fails */
whereBeginError:
if( pWInfo ){
pParse->nQueryLoop = pWInfo->savedNQueryLoop;
whereInfoFree(db, pWInfo);
}
return 0;
}
/*
** Generate the end of the WHERE loop. See comments on
** sqlite3WhereBegin() for additional information.
*/
void sqlite3WhereEnd(WhereInfo *pWInfo){
Parse *pParse = pWInfo->pParse;
Vdbe *v = pParse->pVdbe;
int i;
WhereLevel *pLevel;
SrcList *pTabList = pWInfo->pTabList;
sqlite3 *db = pParse->db;
/* Generate loop termination code.
*/
sqlite3ExprCacheClear(pParse);
for(i=pWInfo->nLevel-1; i>=0; i--){
pLevel = &pWInfo->a[i];
sqlite3VdbeResolveLabel(v, pLevel->addrCont);
if( pLevel->op!=OP_Noop ){
sqlite3VdbeAddOp2(v, pLevel->op, pLevel->p1, pLevel->p2);
sqlite3VdbeChangeP5(v, pLevel->p5);
}
if( pLevel->plan.wsFlags & WHERE_IN_ABLE && pLevel->u.in.nIn>0 ){
struct InLoop *pIn;
int j;
sqlite3VdbeResolveLabel(v, pLevel->addrNxt);
for(j=pLevel->u.in.nIn, pIn=&pLevel->u.in.aInLoop[j-1]; j>0; j--, pIn--){
sqlite3VdbeJumpHere(v, pIn->addrInTop+1);
sqlite3VdbeAddOp2(v, OP_Next, pIn->iCur, pIn->addrInTop);
sqlite3VdbeJumpHere(v, pIn->addrInTop-1);
}
sqlite3DbFree(db, pLevel->u.in.aInLoop);
}
sqlite3VdbeResolveLabel(v, pLevel->addrBrk);
if( pLevel->iLeftJoin ){
int addr;
addr = sqlite3VdbeAddOp1(v, OP_IfPos, pLevel->iLeftJoin);
assert( (pLevel->plan.wsFlags & WHERE_IDX_ONLY)==0
|| (pLevel->plan.wsFlags & WHERE_INDEXED)!=0 );
if( (pLevel->plan.wsFlags & WHERE_IDX_ONLY)==0 ){
sqlite3VdbeAddOp1(v, OP_NullRow, pTabList->a[i].iCursor);
}
if( pLevel->iIdxCur>=0 ){
sqlite3VdbeAddOp1(v, OP_NullRow, pLevel->iIdxCur);
}
if( pLevel->op==OP_Return ){
sqlite3VdbeAddOp2(v, OP_Gosub, pLevel->p1, pLevel->addrFirst);
}else{
sqlite3VdbeAddOp2(v, OP_Goto, 0, pLevel->addrFirst);
}
sqlite3VdbeJumpHere(v, addr);
}
}
/* The "break" point is here, just past the end of the outer loop.
** Set it.
*/
sqlite3VdbeResolveLabel(v, pWInfo->iBreak);
/* Close all of the cursors that were opened by sqlite3WhereBegin.
*/
assert( pWInfo->nLevel==1 || pWInfo->nLevel==pTabList->nSrc );
for(i=0, pLevel=pWInfo->a; i<pWInfo->nLevel; i++, pLevel++){
struct SrcList_item *pTabItem = &pTabList->a[pLevel->iFrom];
Table *pTab = pTabItem->pTab;
assert( pTab!=0 );
if( (pTab->tabFlags & TF_Ephemeral)==0
&& pTab->pSelect==0
&& (pWInfo->wctrlFlags & WHERE_OMIT_CLOSE)==0
){
int ws = pLevel->plan.wsFlags;
if( !pWInfo->okOnePass && (ws & WHERE_IDX_ONLY)==0 ){
sqlite3VdbeAddOp1(v, OP_Close, pTabItem->iCursor);
}
if( (ws & WHERE_INDEXED)!=0 && (ws & WHERE_TEMP_INDEX)==0 ){
sqlite3VdbeAddOp1(v, OP_Close, pLevel->iIdxCur);
}
}
/* If this scan uses an index, make code substitutions to read data
** from the index in preference to the table. Sometimes, this means
** the table need never be read from. This is a performance boost,
** as the vdbe level waits until the table is read before actually
** seeking the table cursor to the record corresponding to the current
** position in the index.
**
** Calls to the code generator in between sqlite3WhereBegin and
** sqlite3WhereEnd will have created code that references the table
** directly. This loop scans all that code looking for opcodes
** that reference the table and converts them into opcodes that
** reference the index.
*/
if( (pLevel->plan.wsFlags & WHERE_INDEXED)!=0 && !db->mallocFailed){
int k, j, last;
VdbeOp *pOp;
Index *pIdx = pLevel->plan.u.pIdx;
assert( pIdx!=0 );
pOp = sqlite3VdbeGetOp(v, pWInfo->iTop);
last = sqlite3VdbeCurrentAddr(v);
for(k=pWInfo->iTop; k<last; k++, pOp++){
if( pOp->p1!=pLevel->iTabCur ) continue;
if( pOp->opcode==OP_Column ){
for(j=0; j<pIdx->nColumn; j++){
if( pOp->p2==pIdx->aiColumn[j] ){
pOp->p2 = j;
pOp->p1 = pLevel->iIdxCur;
break;
}
}
assert( (pLevel->plan.wsFlags & WHERE_IDX_ONLY)==0
|| j<pIdx->nColumn );
}else if( pOp->opcode==OP_Rowid ){
pOp->p1 = pLevel->iIdxCur;
pOp->opcode = OP_IdxRowid;
}
}
}
}
/* Final cleanup
*/
pParse->nQueryLoop = pWInfo->savedNQueryLoop;
whereInfoFree(db, pWInfo);
return;
}