"flat_key","key","int_value","string_value"
"chrome_hashed_performance_mark.mark","chrome_hashed_performance_mark.mark","[NULL]","mark2"
"chrome_hashed_performance_mark.mark_hash","chrome_hashed_performance_mark.mark_hash",20,"[NULL]"
"chrome_hashed_performance_mark.site","chrome_hashed_performance_mark.site","[NULL]","site1"
"chrome_hashed_performance_mark.site_hash","chrome_hashed_performance_mark.site_hash",10,"[NULL]"
"event.category","event.category","[NULL]","cat1"
"event.name","event.name","[NULL]","slice1"
"is_root_in_scope","is_root_in_scope",1,"[NULL]"
"source","source","[NULL]","descriptor"
"source_id","source_id",12345,"[NULL]"