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First attempt to use Bloom filters to optimize star-schema queries.

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FossilOrigin-Name: 28161fba9bcde5ae4b36b22d766c881b795af111a3a323c90f6149d0fea9297d
This commit is contained in:
drh
2021-12-04 13:43:57 +00:00
parent 7439d3580c
commit fa35f5c5a7
4 changed files with 126 additions and 13 deletions
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122
src/where.c
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@@ -750,7 +750,7 @@ static int termCanDriveIndex(
** and to set up the WhereLevel object pLevel so that the code generator
** makes use of the automatic index.
*/
static void constructAutomaticIndex(
static SQLITE_NOINLINE void constructAutomaticIndex(
Parse *pParse, /* The parsing context */
WhereClause *pWC, /* The WHERE clause */
SrcItem *pSrc, /* The FROM clause term to get the next index */
@@ -965,6 +965,62 @@ end_auto_index_create:
}
#endif /* SQLITE_OMIT_AUTOMATIC_INDEX */
/*
** Create a Bloom filter for the WhereLevel in the parameter.
*/
static SQLITE_NOINLINE void constructBloomFilter(
WhereInfo *pWInfo, /* The WHERE clause */
WhereLevel *pLevel /* Make a Bloom filter for this FROM term */
){
int addrTop;
int addrCont;
WhereTerm *pTerm;
WhereTerm *pWCEnd;
Parse *pParse = pWInfo->pParse;
Vdbe *v = pParse->pVdbe;
WhereLoop *pLoop = pLevel->pWLoop;
int iCur;
assert( pLoop!=0 );
assert( v!=0 );
iCur = pLevel->iTabCur;
addrCont = sqlite3VdbeMakeLabel(pParse);
addrTop = sqlite3VdbeAddOp0(v, OP_Once);
pLevel->regFilter = ++pParse->nMem;
sqlite3VdbeAddOp1(v, OP_FilterInit, pLevel->regFilter);
sqlite3VdbeAddOp1(v, OP_Rewind, iCur);
pWCEnd = &pWInfo->sWC.a[pWInfo->sWC.nTerm];
for(pTerm=pWInfo->sWC.a; pTerm<pWCEnd; pTerm++){
Expr *pExpr = pTerm->pExpr;
if( (pTerm->wtFlags & TERM_VIRTUAL)==0
&& sqlite3ExprIsTableConstant(pExpr, iCur)
){
sqlite3ExprIfFalse(pParse, pTerm->pExpr, addrCont, SQLITE_JUMPIFNULL);
}
}
if( pLoop->wsFlags & WHERE_IPK ){
int r1 = sqlite3GetTempReg(pParse);
sqlite3VdbeAddOp2(v, OP_Rowid, iCur, r1);
sqlite3VdbeAddOp4Int(v, OP_FilterAdd, pLevel->regFilter, 0, r1, 1);
}else{
Index *pIdx = pLoop->u.btree.pIndex;
int r1 = sqlite3GetTempRange(pParse, pIdx->nKeyCol);
int n = pIdx->nKeyCol;
int jj;
for(jj=0; jj<n; jj++){
int iCol = pIdx->aiColumn[jj];
sqlite3ExprCodeGetColumnOfTable(v, pIdx->pTable, iCur, iCol,r1+jj);
}
sqlite3VdbeAddOp4Int(v, OP_FilterAdd, pLevel->regFilter, 0, r1, n);
}
sqlite3VdbeResolveLabel(v, addrCont);
sqlite3VdbeAddOp2(v, OP_Next, pLevel->iTabCur, addrTop+3);
sqlite3VdbeJumpHere(v, addrTop);
sqlite3VdbeJumpHere(v, addrTop+2);
}
#ifndef SQLITE_OMIT_VIRTUALTABLE
/*
** Allocate and populate an sqlite3_index_info structure. It is the
@@ -4841,6 +4897,49 @@ static SQLITE_NOINLINE Bitmask whereOmitNoopJoin(
return notReady;
}
/*
** Check to see if there are any SEARCH loops that might benefit from
** using a Bloom filter. Consider a Bloom filter if:
**
** (1) The SEARCH happens more than N times where N is the number
** of rows in the table that is being considered for the Bloom
** filter. (TO DO: Make this condition more precise.)
** (2) Most searches are expected to find zero rows
** (3) The table being searched is not the right table of a LEFT JOIN
** (4) Bloom-filter processing is not disabled
**
** This block of code merely checks to see if a Bloom filter would be
** appropriate, and if so sets the WHERE_BLOOMFILTER flag on the
** WhereLoop. The implementation of the Bloom filter comes further
** down where the code for each WhereLoop is generated.
*/
static SQLITE_NOINLINE void whereCheckIfBloomFilterIsUseful(
WhereInfo *pWInfo,
sqlite3 *db
){
int i;
LogEst nSearch;
SrcItem *pItem;
assert( pWInfo->nLevel>=2 );
assert( OptimizationEnabled(db, SQLITE_BloomFilter) );
nSearch = pWInfo->a[0].pWLoop->nOut;
for(i=1; i<pWInfo->nLevel; i++){
WhereLoop *pLoop = pWInfo->a[i].pWLoop;
if( (pLoop->wsFlags & (WHERE_IPK|WHERE_INDEXED))!=0
&& (pLoop->wsFlags & WHERE_COLUMN_EQ)!=0
&& pLoop->nOut<0
&& nSearch > (pItem = &pWInfo->pTabList->a[pLoop->iTab])->pTab->nRowLogEst
&& (pItem->fg.jointype & JT_LEFT)==0
){
pLoop->wsFlags |= WHERE_BLOOMFILTER;
pLoop->wsFlags &= ~WHERE_IDX_ONLY;
WHERETRACE(0xffff, ("-> use Bloom-filter on loop %c\n", pLoop->cId));
}
nSearch += pLoop->nOut;
}
}
/*
** Generate the beginning of the loop used for WHERE clause processing.
** The return value is a pointer to an opaque structure that contains
@@ -5230,6 +5329,15 @@ WhereInfo *sqlite3WhereBegin(
assert( nTabList>0 );
}
/* Check to see if there are any SEARCH loops that might benefit from
** using a Bloom filter.
*/
if( pWInfo->nLevel>=2
&& OptimizationEnabled(db, SQLITE_BloomFilter)
){
whereCheckIfBloomFilterIsUseful(pWInfo, db);
}
#if defined(WHERETRACE_ENABLED)
if( sqlite3WhereTrace & 0x100 ){ /* Display all terms of the WHERE clause */
sqlite3DebugPrintf("---- WHERE clause at end of analysis:\n");
@@ -5418,13 +5526,17 @@ WhereInfo *sqlite3WhereBegin(
if( pParse->nErr ) goto whereBeginError;
pLevel = &pWInfo->a[ii];
wsFlags = pLevel->pWLoop->wsFlags;
if( (wsFlags & (WHERE_AUTO_INDEX|WHERE_BLOOMFILTER))!=0 ){
if( (wsFlags & WHERE_AUTO_INDEX)!=0 ){
#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
if( (pLevel->pWLoop->wsFlags & WHERE_AUTO_INDEX)!=0 ){
constructAutomaticIndex(pParse, &pWInfo->sWC,
&pTabList->a[pLevel->iFrom], notReady, pLevel);
constructAutomaticIndex(pParse, &pWInfo->sWC,
&pTabList->a[pLevel->iFrom], notReady, pLevel);
#endif
}else{
constructBloomFilter(pWInfo, pLevel);
}
if( db->mallocFailed ) goto whereBeginError;
}
#endif
addrExplain = sqlite3WhereExplainOneScan(
pParse, pTabList, pLevel, wctrlFlags
);