| /* |
| ** 2004 April 6 |
| ** |
| ** 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 file implements a external (disk-based) database using BTrees. |
| ** For a detailed discussion of BTrees, refer to |
| ** |
| ** Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3: |
| ** "Sorting And Searching", pages 473-480. Addison-Wesley |
| ** Publishing Company, Reading, Massachusetts. |
| ** |
| ** The basic idea is that each page of the file contains N database |
| ** entries and N+1 pointers to subpages. |
| ** |
| ** ---------------------------------------------------------------- |
| ** | Ptr(0) | Key(0) | Ptr(1) | Key(1) | ... | Key(N-1) | Ptr(N) | |
| ** ---------------------------------------------------------------- |
| ** |
| ** All of the keys on the page that Ptr(0) points to have values less |
| ** than Key(0). All of the keys on page Ptr(1) and its subpages have |
| ** values greater than Key(0) and less than Key(1). All of the keys |
| ** on Ptr(N) and its subpages have values greater than Key(N-1). And |
| ** so forth. |
| ** |
| ** Finding a particular key requires reading O(log(M)) pages from the |
| ** disk where M is the number of entries in the tree. |
| ** |
| ** In this implementation, a single file can hold one or more separate |
| ** BTrees. Each BTree is identified by the index of its root page. The |
| ** key and data for any entry are combined to form the "payload". A |
| ** fixed amount of payload can be carried directly on the database |
| ** page. If the payload is larger than the preset amount then surplus |
| ** bytes are stored on overflow pages. The payload for an entry |
| ** and the preceding pointer are combined to form a "Cell". Each |
| ** page has a small header which contains the Ptr(N) pointer and other |
| ** information such as the size of key and data. |
| ** |
| ** FORMAT DETAILS |
| ** |
| ** The file is divided into pages. The first page is called page 1, |
| ** the second is page 2, and so forth. A page number of zero indicates |
| ** "no such page". The page size can be any power of 2 between 512 and 65536. |
| ** Each page can be either a btree page, a freelist page, an overflow |
| ** page, or a pointer-map page. |
| ** |
| ** The first page is always a btree page. The first 100 bytes of the first |
| ** page contain a special header (the "file header") that describes the file. |
| ** The format of the file header is as follows: |
| ** |
| ** OFFSET SIZE DESCRIPTION |
| ** 0 16 Header string: "SQLite format 3\000" |
| ** 16 2 Page size in bytes. |
| ** 18 1 File format write version |
| ** 19 1 File format read version |
| ** 20 1 Bytes of unused space at the end of each page |
| ** 21 1 Max embedded payload fraction |
| ** 22 1 Min embedded payload fraction |
| ** 23 1 Min leaf payload fraction |
| ** 24 4 File change counter |
| ** 28 4 Reserved for future use |
| ** 32 4 First freelist page |
| ** 36 4 Number of freelist pages in the file |
| ** 40 60 15 4-byte meta values passed to higher layers |
| ** |
| ** 40 4 Schema cookie |
| ** 44 4 File format of schema layer |
| ** 48 4 Size of page cache |
| ** 52 4 Largest root-page (auto/incr_vacuum) |
| ** 56 4 1=UTF-8 2=UTF16le 3=UTF16be |
| ** 60 4 User version |
| ** 64 4 Incremental vacuum mode |
| ** 68 4 unused |
| ** 72 4 unused |
| ** 76 4 unused |
| ** |
| ** All of the integer values are big-endian (most significant byte first). |
| ** |
| ** The file change counter is incremented when the database is changed |
| ** This counter allows other processes to know when the file has changed |
| ** and thus when they need to flush their cache. |
| ** |
| ** The max embedded payload fraction is the amount of the total usable |
| ** space in a page that can be consumed by a single cell for standard |
| ** B-tree (non-LEAFDATA) tables. A value of 255 means 100%. The default |
| ** is to limit the maximum cell size so that at least 4 cells will fit |
| ** on one page. Thus the default max embedded payload fraction is 64. |
| ** |
| ** If the payload for a cell is larger than the max payload, then extra |
| ** payload is spilled to overflow pages. Once an overflow page is allocated, |
| ** as many bytes as possible are moved into the overflow pages without letting |
| ** the cell size drop below the min embedded payload fraction. |
| ** |
| ** The min leaf payload fraction is like the min embedded payload fraction |
| ** except that it applies to leaf nodes in a LEAFDATA tree. The maximum |
| ** payload fraction for a LEAFDATA tree is always 100% (or 255) and it |
| ** not specified in the header. |
| ** |
| ** Each btree pages is divided into three sections: The header, the |
| ** cell pointer array, and the cell content area. Page 1 also has a 100-byte |
| ** file header that occurs before the page header. |
| ** |
| ** |----------------| |
| ** | file header | 100 bytes. Page 1 only. |
| ** |----------------| |
| ** | page header | 8 bytes for leaves. 12 bytes for interior nodes |
| ** |----------------| |
| ** | cell pointer | | 2 bytes per cell. Sorted order. |
| ** | array | | Grows downward |
| ** | | v |
| ** |----------------| |
| ** | unallocated | |
| ** | space | |
| ** |----------------| ^ Grows upwards |
| ** | cell content | | Arbitrary order interspersed with freeblocks. |
| ** | area | | and free space fragments. |
| ** |----------------| |
| ** |
| ** The page headers looks like this: |
| ** |
| ** OFFSET SIZE DESCRIPTION |
| ** 0 1 Flags. 1: intkey, 2: zerodata, 4: leafdata, 8: leaf |
| ** 1 2 byte offset to the first freeblock |
| ** 3 2 number of cells on this page |
| ** 5 2 first byte of the cell content area |
| ** 7 1 number of fragmented free bytes |
| ** 8 4 Right child (the Ptr(N) value). Omitted on leaves. |
| ** |
| ** The flags define the format of this btree page. The leaf flag means that |
| ** this page has no children. The zerodata flag means that this page carries |
| ** only keys and no data. The intkey flag means that the key is a integer |
| ** which is stored in the key size entry of the cell header rather than in |
| ** the payload area. |
| ** |
| ** The cell pointer array begins on the first byte after the page header. |
| ** The cell pointer array contains zero or more 2-byte numbers which are |
| ** offsets from the beginning of the page to the cell content in the cell |
| ** content area. The cell pointers occur in sorted order. The system strives |
| ** to keep free space after the last cell pointer so that new cells can |
| ** be easily added without having to defragment the page. |
| ** |
| ** Cell content is stored at the very end of the page and grows toward the |
| ** beginning of the page. |
| ** |
| ** Unused space within the cell content area is collected into a linked list of |
| ** freeblocks. Each freeblock is at least 4 bytes in size. The byte offset |
| ** to the first freeblock is given in the header. Freeblocks occur in |
| ** increasing order. Because a freeblock must be at least 4 bytes in size, |
| ** any group of 3 or fewer unused bytes in the cell content area cannot |
| ** exist on the freeblock chain. A group of 3 or fewer free bytes is called |
| ** a fragment. The total number of bytes in all fragments is recorded. |
| ** in the page header at offset 7. |
| ** |
| ** SIZE DESCRIPTION |
| ** 2 Byte offset of the next freeblock |
| ** 2 Bytes in this freeblock |
| ** |
| ** Cells are of variable length. Cells are stored in the cell content area at |
| ** the end of the page. Pointers to the cells are in the cell pointer array |
| ** that immediately follows the page header. Cells is not necessarily |
| ** contiguous or in order, but cell pointers are contiguous and in order. |
| ** |
| ** Cell content makes use of variable length integers. A variable |
| ** length integer is 1 to 9 bytes where the lower 7 bits of each |
| ** byte are used. The integer consists of all bytes that have bit 8 set and |
| ** the first byte with bit 8 clear. The most significant byte of the integer |
| ** appears first. A variable-length integer may not be more than 9 bytes long. |
| ** As a special case, all 8 bytes of the 9th byte are used as data. This |
| ** allows a 64-bit integer to be encoded in 9 bytes. |
| ** |
| ** 0x00 becomes 0x00000000 |
| ** 0x7f becomes 0x0000007f |
| ** 0x81 0x00 becomes 0x00000080 |
| ** 0x82 0x00 becomes 0x00000100 |
| ** 0x80 0x7f becomes 0x0000007f |
| ** 0x8a 0x91 0xd1 0xac 0x78 becomes 0x12345678 |
| ** 0x81 0x81 0x81 0x81 0x01 becomes 0x10204081 |
| ** |
| ** Variable length integers are used for rowids and to hold the number of |
| ** bytes of key and data in a btree cell. |
| ** |
| ** The content of a cell looks like this: |
| ** |
| ** SIZE DESCRIPTION |
| ** 4 Page number of the left child. Omitted if leaf flag is set. |
| ** var Number of bytes of data. Omitted if the zerodata flag is set. |
| ** var Number of bytes of key. Or the key itself if intkey flag is set. |
| ** * Payload |
| ** 4 First page of the overflow chain. Omitted if no overflow |
| ** |
| ** Overflow pages form a linked list. Each page except the last is completely |
| ** filled with data (pagesize - 4 bytes). The last page can have as little |
| ** as 1 byte of data. |
| ** |
| ** SIZE DESCRIPTION |
| ** 4 Page number of next overflow page |
| ** * Data |
| ** |
| ** Freelist pages come in two subtypes: trunk pages and leaf pages. The |
| ** file header points to the first in a linked list of trunk page. Each trunk |
| ** page points to multiple leaf pages. The content of a leaf page is |
| ** unspecified. A trunk page looks like this: |
| ** |
| ** SIZE DESCRIPTION |
| ** 4 Page number of next trunk page |
| ** 4 Number of leaf pointers on this page |
| ** * zero or more pages numbers of leaves |
| */ |
| #include "sqliteInt.h" |
| |
| |
| /* The following value is the maximum cell size assuming a maximum page |
| ** size give above. |
| */ |
| #define MX_CELL_SIZE(pBt) ((int)(pBt->pageSize-8)) |
| |
| /* The maximum number of cells on a single page of the database. This |
| ** assumes a minimum cell size of 6 bytes (4 bytes for the cell itself |
| ** plus 2 bytes for the index to the cell in the page header). Such |
| ** small cells will be rare, but they are possible. |
| */ |
| #define MX_CELL(pBt) ((pBt->pageSize-8)/6) |
| |
| /* Forward declarations */ |
| typedef struct MemPage MemPage; |
| typedef struct BtLock BtLock; |
| |
| /* |
| ** This is a magic string that appears at the beginning of every |
| ** SQLite database in order to identify the file as a real database. |
| ** |
| ** You can change this value at compile-time by specifying a |
| ** -DSQLITE_FILE_HEADER="..." on the compiler command-line. The |
| ** header must be exactly 16 bytes including the zero-terminator so |
| ** the string itself should be 15 characters long. If you change |
| ** the header, then your custom library will not be able to read |
| ** databases generated by the standard tools and the standard tools |
| ** will not be able to read databases created by your custom library. |
| */ |
| #ifndef SQLITE_FILE_HEADER /* 123456789 123456 */ |
| # define SQLITE_FILE_HEADER "SQLite format 3" |
| #endif |
| |
| /* |
| ** Page type flags. An ORed combination of these flags appear as the |
| ** first byte of on-disk image of every BTree page. |
| */ |
| #define PTF_INTKEY 0x01 |
| #define PTF_ZERODATA 0x02 |
| #define PTF_LEAFDATA 0x04 |
| #define PTF_LEAF 0x08 |
| |
| /* |
| ** As each page of the file is loaded into memory, an instance of the following |
| ** structure is appended and initialized to zero. This structure stores |
| ** information about the page that is decoded from the raw file page. |
| ** |
| ** The pParent field points back to the parent page. This allows us to |
| ** walk up the BTree from any leaf to the root. Care must be taken to |
| ** unref() the parent page pointer when this page is no longer referenced. |
| ** The pageDestructor() routine handles that chore. |
| ** |
| ** Access to all fields of this structure is controlled by the mutex |
| ** stored in MemPage.pBt->mutex. |
| */ |
| struct MemPage { |
| u8 isInit; /* True if previously initialized. MUST BE FIRST! */ |
| u8 nOverflow; /* Number of overflow cell bodies in aCell[] */ |
| u8 intKey; /* True if intkey flag is set */ |
| u8 leaf; /* True if leaf flag is set */ |
| u8 hasData; /* True if this page stores data */ |
| u8 hdrOffset; /* 100 for page 1. 0 otherwise */ |
| u8 childPtrSize; /* 0 if leaf==1. 4 if leaf==0 */ |
| u16 maxLocal; /* Copy of BtShared.maxLocal or BtShared.maxLeaf */ |
| u16 minLocal; /* Copy of BtShared.minLocal or BtShared.minLeaf */ |
| u16 cellOffset; /* Index in aData of first cell pointer */ |
| u16 nFree; /* Number of free bytes on the page */ |
| u16 nCell; /* Number of cells on this page, local and ovfl */ |
| u16 maskPage; /* Mask for page offset */ |
| struct _OvflCell { /* Cells that will not fit on aData[] */ |
| u8 *pCell; /* Pointers to the body of the overflow cell */ |
| u16 idx; /* Insert this cell before idx-th non-overflow cell */ |
| } aOvfl[5]; |
| BtShared *pBt; /* Pointer to BtShared that this page is part of */ |
| u8 *aData; /* Pointer to disk image of the page data */ |
| DbPage *pDbPage; /* Pager page handle */ |
| Pgno pgno; /* Page number for this page */ |
| }; |
| |
| /* |
| ** The in-memory image of a disk page has the auxiliary information appended |
| ** to the end. EXTRA_SIZE is the number of bytes of space needed to hold |
| ** that extra information. |
| */ |
| #define EXTRA_SIZE sizeof(MemPage) |
| |
| /* |
| ** A linked list of the following structures is stored at BtShared.pLock. |
| ** Locks are added (or upgraded from READ_LOCK to WRITE_LOCK) when a cursor |
| ** is opened on the table with root page BtShared.iTable. Locks are removed |
| ** from this list when a transaction is committed or rolled back, or when |
| ** a btree handle is closed. |
| */ |
| struct BtLock { |
| Btree *pBtree; /* Btree handle holding this lock */ |
| Pgno iTable; /* Root page of table */ |
| u8 eLock; /* READ_LOCK or WRITE_LOCK */ |
| BtLock *pNext; /* Next in BtShared.pLock list */ |
| }; |
| |
| /* Candidate values for BtLock.eLock */ |
| #define READ_LOCK 1 |
| #define WRITE_LOCK 2 |
| |
| /* A Btree handle |
| ** |
| ** A database connection contains a pointer to an instance of |
| ** this object for every database file that it has open. This structure |
| ** is opaque to the database connection. The database connection cannot |
| ** see the internals of this structure and only deals with pointers to |
| ** this structure. |
| ** |
| ** For some database files, the same underlying database cache might be |
| ** shared between multiple connections. In that case, each connection |
| ** has it own instance of this object. But each instance of this object |
| ** points to the same BtShared object. The database cache and the |
| ** schema associated with the database file are all contained within |
| ** the BtShared object. |
| ** |
| ** All fields in this structure are accessed under sqlite3.mutex. |
| ** The pBt pointer itself may not be changed while there exists cursors |
| ** in the referenced BtShared that point back to this Btree since those |
| ** cursors have to go through this Btree to find their BtShared and |
| ** they often do so without holding sqlite3.mutex. |
| */ |
| struct Btree { |
| sqlite3 *db; /* The database connection holding this btree */ |
| BtShared *pBt; /* Sharable content of this btree */ |
| u8 inTrans; /* TRANS_NONE, TRANS_READ or TRANS_WRITE */ |
| u8 sharable; /* True if we can share pBt with another db */ |
| u8 locked; /* True if db currently has pBt locked */ |
| int wantToLock; /* Number of nested calls to sqlite3BtreeEnter() */ |
| int nBackup; /* Number of backup operations reading this btree */ |
| Btree *pNext; /* List of other sharable Btrees from the same db */ |
| Btree *pPrev; /* Back pointer of the same list */ |
| #ifndef SQLITE_OMIT_SHARED_CACHE |
| BtLock lock; /* Object used to lock page 1 */ |
| #endif |
| }; |
| |
| /* |
| ** Btree.inTrans may take one of the following values. |
| ** |
| ** If the shared-data extension is enabled, there may be multiple users |
| ** of the Btree structure. At most one of these may open a write transaction, |
| ** but any number may have active read transactions. |
| */ |
| #define TRANS_NONE 0 |
| #define TRANS_READ 1 |
| #define TRANS_WRITE 2 |
| |
| /* |
| ** An instance of this object represents a single database file. |
| ** |
| ** A single database file can be in use as the same time by two |
| ** or more database connections. When two or more connections are |
| ** sharing the same database file, each connection has it own |
| ** private Btree object for the file and each of those Btrees points |
| ** to this one BtShared object. BtShared.nRef is the number of |
| ** connections currently sharing this database file. |
| ** |
| ** Fields in this structure are accessed under the BtShared.mutex |
| ** mutex, except for nRef and pNext which are accessed under the |
| ** global SQLITE_MUTEX_STATIC_MASTER mutex. The pPager field |
| ** may not be modified once it is initially set as long as nRef>0. |
| ** The pSchema field may be set once under BtShared.mutex and |
| ** thereafter is unchanged as long as nRef>0. |
| ** |
| ** isPending: |
| ** |
| ** If a BtShared client fails to obtain a write-lock on a database |
| ** table (because there exists one or more read-locks on the table), |
| ** the shared-cache enters 'pending-lock' state and isPending is |
| ** set to true. |
| ** |
| ** The shared-cache leaves the 'pending lock' state when either of |
| ** the following occur: |
| ** |
| ** 1) The current writer (BtShared.pWriter) concludes its transaction, OR |
| ** 2) The number of locks held by other connections drops to zero. |
| ** |
| ** while in the 'pending-lock' state, no connection may start a new |
| ** transaction. |
| ** |
| ** This feature is included to help prevent writer-starvation. |
| */ |
| struct BtShared { |
| Pager *pPager; /* The page cache */ |
| sqlite3 *db; /* Database connection currently using this Btree */ |
| BtCursor *pCursor; /* A list of all open cursors */ |
| MemPage *pPage1; /* First page of the database */ |
| u8 readOnly; /* True if the underlying file is readonly */ |
| u8 pageSizeFixed; /* True if the page size can no longer be changed */ |
| u8 secureDelete; /* True if secure_delete is enabled */ |
| u8 initiallyEmpty; /* Database is empty at start of transaction */ |
| u8 openFlags; /* Flags to sqlite3BtreeOpen() */ |
| #ifndef SQLITE_OMIT_AUTOVACUUM |
| u8 autoVacuum; /* True if auto-vacuum is enabled */ |
| u8 incrVacuum; /* True if incr-vacuum is enabled */ |
| #endif |
| u8 inTransaction; /* Transaction state */ |
| u8 doNotUseWAL; /* If true, do not open write-ahead-log file */ |
| u16 maxLocal; /* Maximum local payload in non-LEAFDATA tables */ |
| u16 minLocal; /* Minimum local payload in non-LEAFDATA tables */ |
| u16 maxLeaf; /* Maximum local payload in a LEAFDATA table */ |
| u16 minLeaf; /* Minimum local payload in a LEAFDATA table */ |
| u32 pageSize; /* Total number of bytes on a page */ |
| u32 usableSize; /* Number of usable bytes on each page */ |
| int nTransaction; /* Number of open transactions (read + write) */ |
| u32 nPage; /* Number of pages in the database */ |
| void *pSchema; /* Pointer to space allocated by sqlite3BtreeSchema() */ |
| void (*xFreeSchema)(void*); /* Destructor for BtShared.pSchema */ |
| sqlite3_mutex *mutex; /* Non-recursive mutex required to access this object */ |
| Bitvec *pHasContent; /* Set of pages moved to free-list this transaction */ |
| #ifndef SQLITE_OMIT_SHARED_CACHE |
| int nRef; /* Number of references to this structure */ |
| BtShared *pNext; /* Next on a list of sharable BtShared structs */ |
| BtLock *pLock; /* List of locks held on this shared-btree struct */ |
| Btree *pWriter; /* Btree with currently open write transaction */ |
| u8 isExclusive; /* True if pWriter has an EXCLUSIVE lock on the db */ |
| u8 isPending; /* If waiting for read-locks to clear */ |
| #endif |
| u8 *pTmpSpace; /* BtShared.pageSize bytes of space for tmp use */ |
| }; |
| |
| /* |
| ** An instance of the following structure is used to hold information |
| ** about a cell. The parseCellPtr() function fills in this structure |
| ** based on information extract from the raw disk page. |
| */ |
| typedef struct CellInfo CellInfo; |
| struct CellInfo { |
| i64 nKey; /* The key for INTKEY tables, or number of bytes in key */ |
| u8 *pCell; /* Pointer to the start of cell content */ |
| u32 nData; /* Number of bytes of data */ |
| u32 nPayload; /* Total amount of payload */ |
| u16 nHeader; /* Size of the cell content header in bytes */ |
| u16 nLocal; /* Amount of payload held locally */ |
| u16 iOverflow; /* Offset to overflow page number. Zero if no overflow */ |
| u16 nSize; /* Size of the cell content on the main b-tree page */ |
| }; |
| |
| /* |
| ** Maximum depth of an SQLite B-Tree structure. Any B-Tree deeper than |
| ** this will be declared corrupt. This value is calculated based on a |
| ** maximum database size of 2^31 pages a minimum fanout of 2 for a |
| ** root-node and 3 for all other internal nodes. |
| ** |
| ** If a tree that appears to be taller than this is encountered, it is |
| ** assumed that the database is corrupt. |
| */ |
| #define BTCURSOR_MAX_DEPTH 20 |
| |
| /* |
| ** A cursor is a pointer to a particular entry within a particular |
| ** b-tree within a database file. |
| ** |
| ** The entry is identified by its MemPage and the index in |
| ** MemPage.aCell[] of the entry. |
| ** |
| ** A single database file can shared by two more database connections, |
| ** but cursors cannot be shared. Each cursor is associated with a |
| ** particular database connection identified BtCursor.pBtree.db. |
| ** |
| ** Fields in this structure are accessed under the BtShared.mutex |
| ** found at self->pBt->mutex. |
| */ |
| struct BtCursor { |
| Btree *pBtree; /* The Btree to which this cursor belongs */ |
| BtShared *pBt; /* The BtShared this cursor points to */ |
| BtCursor *pNext, *pPrev; /* Forms a linked list of all cursors */ |
| struct KeyInfo *pKeyInfo; /* Argument passed to comparison function */ |
| Pgno pgnoRoot; /* The root page of this tree */ |
| sqlite3_int64 cachedRowid; /* Next rowid cache. 0 means not valid */ |
| CellInfo info; /* A parse of the cell we are pointing at */ |
| i64 nKey; /* Size of pKey, or last integer key */ |
| void *pKey; /* Saved key that was cursor's last known position */ |
| int skipNext; /* Prev() is noop if negative. Next() is noop if positive */ |
| u8 wrFlag; /* True if writable */ |
| u8 atLast; /* Cursor pointing to the last entry */ |
| u8 validNKey; /* True if info.nKey is valid */ |
| u8 eState; /* One of the CURSOR_XXX constants (see below) */ |
| #ifndef SQLITE_OMIT_INCRBLOB |
| Pgno *aOverflow; /* Cache of overflow page locations */ |
| u8 isIncrblobHandle; /* True if this cursor is an incr. io handle */ |
| #endif |
| i16 iPage; /* Index of current page in apPage */ |
| u16 aiIdx[BTCURSOR_MAX_DEPTH]; /* Current index in apPage[i] */ |
| MemPage *apPage[BTCURSOR_MAX_DEPTH]; /* Pages from root to current page */ |
| }; |
| |
| /* |
| ** Potential values for BtCursor.eState. |
| ** |
| ** CURSOR_VALID: |
| ** Cursor points to a valid entry. getPayload() etc. may be called. |
| ** |
| ** CURSOR_INVALID: |
| ** Cursor does not point to a valid entry. This can happen (for example) |
| ** because the table is empty or because BtreeCursorFirst() has not been |
| ** called. |
| ** |
| ** CURSOR_REQUIRESEEK: |
| ** The table that this cursor was opened on still exists, but has been |
| ** modified since the cursor was last used. The cursor position is saved |
| ** in variables BtCursor.pKey and BtCursor.nKey. When a cursor is in |
| ** this state, restoreCursorPosition() can be called to attempt to |
| ** seek the cursor to the saved position. |
| ** |
| ** CURSOR_FAULT: |
| ** A unrecoverable error (an I/O error or a malloc failure) has occurred |
| ** on a different connection that shares the BtShared cache with this |
| ** cursor. The error has left the cache in an inconsistent state. |
| ** Do nothing else with this cursor. Any attempt to use the cursor |
| ** should return the error code stored in BtCursor.skip |
| */ |
| #define CURSOR_INVALID 0 |
| #define CURSOR_VALID 1 |
| #define CURSOR_REQUIRESEEK 2 |
| #define CURSOR_FAULT 3 |
| |
| /* |
| ** The database page the PENDING_BYTE occupies. This page is never used. |
| */ |
| # define PENDING_BYTE_PAGE(pBt) PAGER_MJ_PGNO(pBt) |
| |
| /* |
| ** These macros define the location of the pointer-map entry for a |
| ** database page. The first argument to each is the number of usable |
| ** bytes on each page of the database (often 1024). The second is the |
| ** page number to look up in the pointer map. |
| ** |
| ** PTRMAP_PAGENO returns the database page number of the pointer-map |
| ** page that stores the required pointer. PTRMAP_PTROFFSET returns |
| ** the offset of the requested map entry. |
| ** |
| ** If the pgno argument passed to PTRMAP_PAGENO is a pointer-map page, |
| ** then pgno is returned. So (pgno==PTRMAP_PAGENO(pgsz, pgno)) can be |
| ** used to test if pgno is a pointer-map page. PTRMAP_ISPAGE implements |
| ** this test. |
| */ |
| #define PTRMAP_PAGENO(pBt, pgno) ptrmapPageno(pBt, pgno) |
| #define PTRMAP_PTROFFSET(pgptrmap, pgno) (5*(pgno-pgptrmap-1)) |
| #define PTRMAP_ISPAGE(pBt, pgno) (PTRMAP_PAGENO((pBt),(pgno))==(pgno)) |
| |
| /* |
| ** The pointer map is a lookup table that identifies the parent page for |
| ** each child page in the database file. The parent page is the page that |
| ** contains a pointer to the child. Every page in the database contains |
| ** 0 or 1 parent pages. (In this context 'database page' refers |
| ** to any page that is not part of the pointer map itself.) Each pointer map |
| ** entry consists of a single byte 'type' and a 4 byte parent page number. |
| ** The PTRMAP_XXX identifiers below are the valid types. |
| ** |
| ** The purpose of the pointer map is to facility moving pages from one |
| ** position in the file to another as part of autovacuum. When a page |
| ** is moved, the pointer in its parent must be updated to point to the |
| ** new location. The pointer map is used to locate the parent page quickly. |
| ** |
| ** PTRMAP_ROOTPAGE: The database page is a root-page. The page-number is not |
| ** used in this case. |
| ** |
| ** PTRMAP_FREEPAGE: The database page is an unused (free) page. The page-number |
| ** is not used in this case. |
| ** |
| ** PTRMAP_OVERFLOW1: The database page is the first page in a list of |
| ** overflow pages. The page number identifies the page that |
| ** contains the cell with a pointer to this overflow page. |
| ** |
| ** PTRMAP_OVERFLOW2: The database page is the second or later page in a list of |
| ** overflow pages. The page-number identifies the previous |
| ** page in the overflow page list. |
| ** |
| ** PTRMAP_BTREE: The database page is a non-root btree page. The page number |
| ** identifies the parent page in the btree. |
| */ |
| #define PTRMAP_ROOTPAGE 1 |
| #define PTRMAP_FREEPAGE 2 |
| #define PTRMAP_OVERFLOW1 3 |
| #define PTRMAP_OVERFLOW2 4 |
| #define PTRMAP_BTREE 5 |
| |
| /* A bunch of assert() statements to check the transaction state variables |
| ** of handle p (type Btree*) are internally consistent. |
| */ |
| #define btreeIntegrity(p) \ |
| assert( p->pBt->inTransaction!=TRANS_NONE || p->pBt->nTransaction==0 ); \ |
| assert( p->pBt->inTransaction>=p->inTrans ); |
| |
| |
| /* |
| ** The ISAUTOVACUUM macro is used within balance_nonroot() to determine |
| ** if the database supports auto-vacuum or not. Because it is used |
| ** within an expression that is an argument to another macro |
| ** (sqliteMallocRaw), it is not possible to use conditional compilation. |
| ** So, this macro is defined instead. |
| */ |
| #ifndef SQLITE_OMIT_AUTOVACUUM |
| #define ISAUTOVACUUM (pBt->autoVacuum) |
| #else |
| #define ISAUTOVACUUM 0 |
| #endif |
| |
| |
| /* |
| ** This structure is passed around through all the sanity checking routines |
| ** in order to keep track of some global state information. |
| */ |
| typedef struct IntegrityCk IntegrityCk; |
| struct IntegrityCk { |
| BtShared *pBt; /* The tree being checked out */ |
| Pager *pPager; /* The associated pager. Also accessible by pBt->pPager */ |
| Pgno nPage; /* Number of pages in the database */ |
| int *anRef; /* Number of times each page is referenced */ |
| int mxErr; /* Stop accumulating errors when this reaches zero */ |
| int nErr; /* Number of messages written to zErrMsg so far */ |
| int mallocFailed; /* A memory allocation error has occurred */ |
| StrAccum errMsg; /* Accumulate the error message text here */ |
| }; |
| |
| /* |
| ** Read or write a two- and four-byte big-endian integer values. |
| */ |
| #define get2byte(x) ((x)[0]<<8 | (x)[1]) |
| #define put2byte(p,v) ((p)[0] = (u8)((v)>>8), (p)[1] = (u8)(v)) |
| #define get4byte sqlite3Get4byte |
| #define put4byte sqlite3Put4byte |