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Improve GIN indexscan cost estimation.

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The better estimate requires more statistics than we previously stored:
in particular, counts of "entry" versus "data" pages within the index,
as well as knowledge of the number of distinct key values.  We collect
this information during initial index build and update it during VACUUM,
storing the info in new fields on the index metapage.  No initdb is
required because these fields will read as zeroes in a pre-existing
index, and the new gincostestimate code is coded to behave (reasonably)
sanely if they are zeroes.

Teodor Sigaev, reviewed by Jan Urbanski, Tom Lane, and Itagaki Takahiro.
This commit is contained in:
Tom Lane
2010-10-17 20:52:32 -04:00
parent cd0e825321
commit 48c7d9f6ff
10 changed files with 561 additions and 42 deletions
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36
src/include/access/gin.h
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@@ -79,6 +79,14 @@ typedef struct GinMetaPageData
*/
BlockNumber nPendingPages;
int64 nPendingHeapTuples;
/*
* Statistics for planner use (accurate as of last VACUUM)
*/
BlockNumber nTotalPages;
BlockNumber nEntryPages;
BlockNumber nDataPages;
int64 nEntries;
} GinMetaPageData;
#define GinPageGetMeta(p) \
@@ -94,6 +102,8 @@ typedef struct GinMetaPageData
#define GinPageSetNonLeaf(page) ( GinPageGetOpaque(page)->flags &= ~GIN_LEAF )
#define GinPageIsData(page) ( GinPageGetOpaque(page)->flags & GIN_DATA )
#define GinPageSetData(page) ( GinPageGetOpaque(page)->flags |= GIN_DATA )
#define GinPageIsList(page) ( GinPageGetOpaque(page)->flags & GIN_LIST )
#define GinPageSetList(page) ( GinPageGetOpaque(page)->flags |= GIN_LIST )
#define GinPageHasFullRow(page) ( GinPageGetOpaque(page)->flags & GIN_LIST_FULLROW )
#define GinPageSetFullRow(page) ( GinPageGetOpaque(page)->flags |= GIN_LIST_FULLROW )
@@ -362,13 +372,28 @@ extern Datum *extractEntriesSU(GinState *ginstate, OffsetNumber attnum, Datum va
extern Datum gin_index_getattr(GinState *ginstate, IndexTuple tuple);
extern OffsetNumber gintuple_get_attrnum(GinState *ginstate, IndexTuple tuple);
/*
* GinStatsData represents stats data for planner use
*/
typedef struct GinStatsData
{
BlockNumber nPendingPages;
BlockNumber nTotalPages;
BlockNumber nEntryPages;
BlockNumber nDataPages;
int64 nEntries;
} GinStatsData;
extern void ginGetStats(Relation index, GinStatsData *stats);
extern void ginUpdateStats(Relation index, const GinStatsData *stats);
/* gininsert.c */
extern Datum ginbuild(PG_FUNCTION_ARGS);
extern Datum gininsert(PG_FUNCTION_ARGS);
extern void ginEntryInsert(Relation index, GinState *ginstate,
OffsetNumber attnum, Datum value,
ItemPointerData *items, uint32 nitem,
bool isBuild);
GinStatsData *buildStats);
/* ginxlog.c */
extern void gin_redo(XLogRecPtr lsn, XLogRecord *record);
@@ -406,6 +431,7 @@ typedef struct GinBtreeData
Page (*splitPage) (GinBtree, Buffer, Buffer, OffsetNumber, XLogRecData **);
void (*fillRoot) (GinBtree, Buffer, Buffer, Buffer);
bool isData;
bool searchMode;
Relation index;
@@ -432,7 +458,8 @@ typedef struct GinBtreeData
extern GinBtreeStack *ginPrepareFindLeafPage(GinBtree btree, BlockNumber blkno);
extern GinBtreeStack *ginFindLeafPage(GinBtree btree, GinBtreeStack *stack);
extern void freeGinBtreeStack(GinBtreeStack *stack);
extern void ginInsertValue(GinBtree btree, GinBtreeStack *stack);
extern void ginInsertValue(GinBtree btree, GinBtreeStack *stack,
GinStatsData *buildStats);
extern void findParents(GinBtree btree, GinBtreeStack *stack, BlockNumber rootBlkno);
/* ginentrypage.c */
@@ -462,8 +489,9 @@ typedef struct
extern GinPostingTreeScan *prepareScanPostingTree(Relation index,
BlockNumber rootBlkno, bool searchMode);
extern void insertItemPointer(GinPostingTreeScan *gdi,
ItemPointerData *items, uint32 nitem);
extern void ginInsertItemPointer(GinPostingTreeScan *gdi,
ItemPointerData *items, uint32 nitem,
GinStatsData *buildStats);
extern Buffer scanBeginPostingTree(GinPostingTreeScan *gdi);
extern void dataFillRoot(GinBtree btree, Buffer root, Buffer lbuf, Buffer rbuf);
extern void prepareDataScan(GinBtree btree, Relation index);