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Enhance the query planner so that it looks at multiple solutions to OR

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expressions in the WHERE clause.

FossilOrigin-Name: 5e19d054105fb16ff52d265d48cc87a418603f6f
This commit is contained in:
drh
2013-07-16 21:31:23 +00:00
parent 425e27db12
commit aa32e3c60a
5 changed files with 148 additions and 65 deletions
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179
src/where.c
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@@ -45,6 +45,8 @@ typedef struct WherePath WherePath;
typedef struct WhereTerm WhereTerm;
typedef struct WhereLoopBuilder WhereLoopBuilder;
typedef struct WhereScan WhereScan;
typedef struct WhereOrCost WhereOrCost;
typedef struct WhereOrSet WhereOrSet;
/*
** Cost X is tracked as 10*log2(X) stored in a 16-bit integer. The
@@ -152,6 +154,27 @@ struct WhereLoop {
WhereTerm *aLTermSpace[4]; /* Initial aLTerm[] space */
};
/* This object holds the prerequisites and the cost of running a
** subquery on one operand of an OR operator in the WHERE clause.
** See WhereOrSet for additional information
*/
struct WhereOrCost {
Bitmask prereq; /* Prerequisites */
WhereCost rRun; /* Cost of running this subquery */
WhereCost nOut; /* Number of outputs for this subquery */
};
/* The WhereOrSet object holds a set of possible WhereOrCosts that
** correspond to the subquery(s) of OR-clause processing. At most
** favorable N_OR_COST elements are retained.
*/
#define N_OR_COST 3
struct WhereOrSet {
u16 n; /* Number of valid a[] entries */
WhereOrCost a[N_OR_COST]; /* Set of best costs */
};
/* Forward declaration of methods */
static int whereLoopResize(sqlite3*, WhereLoop*, int);
@@ -366,7 +389,7 @@ struct WhereLoopBuilder {
WhereClause *pWC; /* WHERE clause terms */
ExprList *pOrderBy; /* ORDER BY clause */
WhereLoop *pNew; /* Template WhereLoop */
WhereLoop *pBest; /* If non-NULL, store single best loop here */
WhereOrSet *pOrSet; /* Record best loops here, if not NULL */
};
/*
@@ -509,6 +532,54 @@ int sqlite3WhereOkOnePass(WhereInfo *pWInfo){
return pWInfo->okOnePass;
}
/*
** Move the content of pSrc into pDest
*/
static void whereOrMove(WhereOrSet *pDest, WhereOrSet *pSrc){
pDest->n = pSrc->n;
memcpy(pDest->a, pSrc->a, pDest->n*sizeof(pDest->a[0]));
}
/*
** Try to insert a new prerequisite/cost entry into the WhereOrSet pSet.
**
** The new entry might overwrite an existing entry, or it might be
** appended, or it might be discarded. Do whatever is the right thing
** so that pSet keeps the N_OR_COST best entries seen so far.
*/
static int whereOrInsert(
WhereOrSet *pSet, /* The WhereOrSet to be updated */
Bitmask prereq, /* Prerequisites of the new entry */
WhereCost rRun, /* Run-cost of the new entry */
WhereCost nOut /* Number of outputs for the new entry */
){
u16 i;
WhereOrCost *p;
for(i=pSet->n, p=pSet->a; i>0; i--, p++){
if( rRun<=p->rRun && (prereq & p->prereq)==prereq ){
goto whereOrInsert_done;
}
if( p->rRun<=rRun && (p->prereq & prereq)==p->prereq ){
return 0;
}
}
if( pSet->n<N_OR_COST ){
p = &pSet->a[pSet->n++];
p->nOut = nOut;
}else{
p = pSet->a;
for(i=1; i<pSet->n; i++){
if( p->rRun>pSet->a[i].rRun ) p = pSet->a + i;
}
if( p->rRun<=rRun ) return 0;
}
whereOrInsert_done:
p->prereq = prereq;
p->rRun = rRun;
if( p->nOut>nOut ) p->nOut = nOut;
return 1;
}
/*
** Initialize a preallocated WhereClause structure.
*/
@@ -3743,8 +3814,9 @@ static Bitmask codeOneLoopStart(
int iTerm;
for(iTerm=0; iTerm<pWC->nTerm; iTerm++){
Expr *pExpr = pWC->a[iTerm].pExpr;
if( &pWC->a[iTerm] == pTerm ) continue;
if( ExprHasProperty(pExpr, EP_FromJoin) ) continue;
if( pWC->a[iTerm].wtFlags & (TERM_VIRTUAL|TERM_ORINFO) ) continue;
if( pWC->a[iTerm].wtFlags & (TERM_ORINFO) ) continue;
if( (pWC->a[iTerm].eOperator & WO_ALL)==0 ) continue;
pExpr = sqlite3ExprDup(pParse->db, pExpr, 0);
pAndExpr = sqlite3ExprAnd(pParse->db, pAndExpr, pExpr);
@@ -4072,12 +4144,12 @@ static void whereInfoFree(sqlite3 *db, WhereInfo *pWInfo){
** fewer dependencies than the template. Otherwise a new WhereLoop is
** added based on the template.
**
** If pBuilder->pBest is not NULL then we only care about the very
** best template and that template should be stored in pBuilder->pBest.
** If pBuilder->pBest is NULL then a list of the best templates are stored
** in pBuilder->pWInfo->pLoops.
** If pBuilder->pOrSet is not NULL then we only care about only the
** prerequisites and rRun and nOut costs of the N best loops. That
** information is gathered in the pBuilder->pOrSet object. This special
** processing mode is used only for OR clause processing.
**
** When accumulating multiple loops (when pBuilder->pBest is NULL) we
** When accumulating multiple loops (when pBuilder->pOrSet is NULL) we
** still might overwrite similar loops with the new template if the
** template is better. Loops may be overwritten if the following
** conditions are met:
@@ -4094,30 +4166,22 @@ static int whereLoopInsert(WhereLoopBuilder *pBuilder, WhereLoop *pTemplate){
WhereInfo *pWInfo = pBuilder->pWInfo;
sqlite3 *db = pWInfo->pParse->db;
/* If pBuilder->pBest is defined, then only keep track of the single
** best WhereLoop. pBuilder->pBest->maskSelf==0 indicates that no
** prior WhereLoops have been evaluated and that the current pTemplate
** is therefore the first and hence the best and should be retained.
/* If pBuilder->pOrSet is defined, then only keep track of the costs
** and prereqs.
*/
if( (p = pBuilder->pBest)!=0 ){
if( p->maskSelf!=0 ){
WhereCost rCost = whereCostAdd(p->rRun,p->rSetup);
WhereCost rTemplate = whereCostAdd(pTemplate->rRun,pTemplate->rSetup);
if( rCost < rTemplate ){
testcase( rCost==rTemplate-1 );
goto whereLoopInsert_noop;
}
if( rCost==rTemplate && (p->prereq & pTemplate->prereq)==p->prereq ){
goto whereLoopInsert_noop;
}
}
if( pBuilder->pOrSet!=0 ){
#if WHERETRACE_ENABLED
u16 n = pBuilder->pOrSet->n;
int x =
#endif
whereOrInsert(pBuilder->pOrSet, pTemplate->prereq, pTemplate->rRun,
pTemplate->nOut);
#if WHERETRACE_ENABLED
if( sqlite3WhereTrace & 0x8 ){
sqlite3DebugPrintf(p->maskSelf==0 ? "ins-init: " : "ins-best: ");
sqlite3DebugPrintf(x?" or-%d: ":" or-X: ", n);
whereLoopPrint(pTemplate, pWInfo->pTabList);
}
#endif
whereLoopXfer(db, p, pTemplate);
return SQLITE_OK;
}
@@ -4211,7 +4275,7 @@ static int whereLoopInsert(WhereLoopBuilder *pBuilder, WhereLoop *pTemplate){
whereLoopInsert_noop:
#if WHERETRACE_ENABLED
if( sqlite3WhereTrace & 0x8 ){
sqlite3DebugPrintf(pBuilder->pBest ? "ins-skip: " : "ins-noop: ");
sqlite3DebugPrintf("ins-noop: ");
whereLoopPrint(pTemplate, pWInfo->pTabList);
}
#endif
@@ -4493,7 +4557,7 @@ static int whereLoopAddBtree(
rLogSize = estLog(rSize);
/* Automatic indexes */
if( !pBuilder->pBest
if( !pBuilder->pOrSet
&& (pWInfo->pParse->db->flags & SQLITE_AutoIndex)!=0
&& pSrc->pIndex==0
&& !pSrc->viaCoroutine
@@ -4779,7 +4843,7 @@ static int whereLoopAddOr(WhereLoopBuilder *pBuilder, Bitmask mExtra){
int iCur;
WhereClause tempWC;
WhereLoopBuilder sSubBuild;
WhereLoop sBest;
WhereOrSet sSum, sCur, sPrev;
struct SrcList_item *pItem;
pWC = pBuilder->pWC;
@@ -4794,16 +4858,14 @@ static int whereLoopAddOr(WhereLoopBuilder *pBuilder, Bitmask mExtra){
WhereClause * const pOrWC = &pTerm->u.pOrInfo->wc;
WhereTerm * const pOrWCEnd = &pOrWC->a[pOrWC->nTerm];
WhereTerm *pOrTerm;
WhereCost rTotal = 0;
WhereCost nRow = 0;
Bitmask prereq = mExtra;
int once = 1;
int i, j;
whereLoopInit(&sBest);
pItem = pWInfo->pTabList->a + pNew->iTab;
iCur = pItem->iCursor;
sSubBuild = *pBuilder;
sSubBuild.pOrderBy = 0;
sSubBuild.pBest = &sBest;
sSubBuild.pOrSet = &sCur;
for(pOrTerm=pOrWC->a; pOrTerm<pOrWCEnd; pOrTerm++){
if( (pOrTerm->eOperator & WO_AND)!=0 ){
@@ -4818,39 +4880,48 @@ static int whereLoopAddOr(WhereLoopBuilder *pBuilder, Bitmask mExtra){
}else{
continue;
}
sBest.maskSelf = 0;
sBest.rSetup = 0;
sBest.rRun = 0;
sCur.n = 0;
#ifndef SQLITE_OMIT_VIRTUALTABLE
if( IsVirtual(pItem->pTab) ){
rc = whereLoopAddVirtual(&sSubBuild);
for(i=0; i<sCur.n; i++) sCur.a[i].prereq |= mExtra;
}else
#endif
{
rc = whereLoopAddBtree(&sSubBuild, mExtra);
}
/* sBest.maskSelf is always zero if an error occurs */
assert( rc==SQLITE_OK || sBest.maskSelf==0 );
if( sBest.maskSelf==0 ) break;
assert( sBest.rSetup==0 );
rTotal = whereCostAdd(rTotal, sBest.rRun);
nRow = whereCostAdd(nRow, sBest.nOut);
prereq |= sBest.prereq;
assert( rc==SQLITE_OK || sCur.n==0 );
if( sCur.n==0 ){
sSum.n = 0;
break;
}else if( once ){
whereOrMove(&sSum, &sCur);
once = 0;
}else{
whereOrMove(&sPrev, &sSum);
sSum.n = 0;
for(i=0; i<sPrev.n; i++){
for(j=0; j<sCur.n; j++){
whereOrInsert(&sSum, sPrev.a[i].prereq | sCur.a[j].prereq,
whereCostAdd(sPrev.a[i].rRun, sCur.a[j].rRun),
whereCostAdd(sPrev.a[i].nOut, sCur.a[j].nOut));
}
}
}
}
assert( pNew->nLSlot>=1 );
if( sBest.maskSelf ){
pNew->nLTerm = 1;
pNew->aLTerm[0] = pTerm;
pNew->wsFlags = WHERE_MULTI_OR;
pNew->rSetup = 0;
pNew->nLTerm = 1;
pNew->aLTerm[0] = pTerm;
pNew->wsFlags = WHERE_MULTI_OR;
pNew->rSetup = 0;
pNew->iSortIdx = 0;
memset(&pNew->u, 0, sizeof(pNew->u));
for(i=0; rc==SQLITE_OK && i<sSum.n; i++){
/* TUNING: Multiple by 3.5 for the secondary table lookup */
pNew->rRun = rTotal + 18; assert( 18==whereCost(7)-whereCost(2) );
pNew->nOut = nRow;
pNew->prereq = prereq;
memset(&pNew->u, 0, sizeof(pNew->u));
pNew->rRun = sSum.a[i].rRun + 18;
pNew->nOut = sSum.a[i].nOut;
pNew->prereq = sSum.a[i].prereq;
rc = whereLoopInsert(pBuilder, pNew);
}
whereLoopClear(pWInfo->pParse->db, &sBest);
}
}
return rc;