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When optimizing out an ORDER BY clause due to uniqueness constraints, make

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sure unused terms to the right in the ORDER BY clause to not reference other
tables in a join.  Ticket #2211.  Additional test cases needed before
closing this ticket. (CVS 3629)

FossilOrigin-Name: 912faf18d86416b1a36660851f8a4554e6746875
This commit is contained in:
drh
2007-02-06 13:26:32 +00:00
parent 8ebf6707cf
commit 7b4fc6a8cb
4 changed files with 137 additions and 35 deletions
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83
src/where.c
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@@ -16,7 +16,7 @@
** so is applicable. Because this module is responsible for selecting
** indices, you might also think of this module as the "query optimizer".
**
** $Id: where.c,v 1.236 2007/01/25 16:56:07 drh Exp $
** $Id: where.c,v 1.237 2007/02/06 13:26:33 drh Exp $
*/
#include "sqliteInt.h"
@@ -43,6 +43,7 @@ int sqlite3_where_trace = 0;
/* Forward reference
*/
typedef struct WhereClause WhereClause;
typedef struct ExprMaskSet ExprMaskSet;
/*
** The query generator uses an array of instances of this structure to
@@ -106,6 +107,7 @@ struct WhereTerm {
*/
struct WhereClause {
Parse *pParse; /* The parser context */
ExprMaskSet *pMaskSet; /* Mapping of table indices to bitmasks */
int nTerm; /* Number of terms */
int nSlot; /* Number of entries in a[] */
WhereTerm *a; /* Each a[] describes a term of the WHERE cluase */
@@ -138,7 +140,6 @@ struct WhereClause {
** numbers all get mapped into bit numbers that begin with 0 and contain
** no gaps.
*/
typedef struct ExprMaskSet ExprMaskSet;
struct ExprMaskSet {
int n; /* Number of assigned cursor values */
int ix[sizeof(Bitmask)*8]; /* Cursor assigned to each bit */
@@ -186,8 +187,13 @@ struct ExprMaskSet {
/*
** Initialize a preallocated WhereClause structure.
*/
static void whereClauseInit(WhereClause *pWC, Parse *pParse){
static void whereClauseInit(
WhereClause *pWC, /* The WhereClause to be initialized */
Parse *pParse, /* The parsing context */
ExprMaskSet *pMaskSet /* Mapping from table indices to bitmasks */
){
pWC->pParse = pParse;
pWC->pMaskSet = pMaskSet;
pWC->nTerm = 0;
pWC->nSlot = ARRAYSIZE(pWC->aStatic);
pWC->a = pWC->aStatic;
@@ -463,7 +469,7 @@ static WhereTerm *findTerm(
}
/* Forward reference */
static void exprAnalyze(SrcList*, ExprMaskSet*, WhereClause*, int);
static void exprAnalyze(SrcList*, WhereClause*, int);
/*
** Call exprAnalyze on all terms in a WHERE clause.
@@ -472,12 +478,11 @@ static void exprAnalyze(SrcList*, ExprMaskSet*, WhereClause*, int);
*/
static void exprAnalyzeAll(
SrcList *pTabList, /* the FROM clause */
ExprMaskSet *pMaskSet, /* table masks */
WhereClause *pWC /* the WHERE clause to be analyzed */
){
int i;
for(i=pWC->nTerm-1; i>=0; i--){
exprAnalyze(pTabList, pMaskSet, pWC, i);
exprAnalyze(pTabList, pWC, i);
}
}
@@ -592,11 +597,11 @@ static void transferJoinMarkings(Expr *pDerived, Expr *pBase){
*/
static void exprAnalyze(
SrcList *pSrc, /* the FROM clause */
ExprMaskSet *pMaskSet, /* table masks */
WhereClause *pWC, /* the WHERE clause */
int idxTerm /* Index of the term to be analyzed */
){
WhereTerm *pTerm = &pWC->a[idxTerm];
ExprMaskSet *pMaskSet = pWC->pMaskSet;
Expr *pExpr = pTerm->pExpr;
Bitmask prereqLeft;
Bitmask prereqAll;
@@ -679,7 +684,7 @@ static void exprAnalyze(
pNewExpr = sqlite3Expr(ops[i], sqlite3ExprDup(pExpr->pLeft),
sqlite3ExprDup(pList->a[i].pExpr), 0);
idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC);
exprAnalyze(pSrc, pMaskSet, pWC, idxNew);
exprAnalyze(pSrc, pWC, idxNew);
pTerm = &pWC->a[idxTerm];
pWC->a[idxNew].iParent = idxTerm;
}
@@ -708,9 +713,9 @@ static void exprAnalyze(
WhereTerm *pOrTerm;
assert( (pTerm->flags & TERM_DYNAMIC)==0 );
whereClauseInit(&sOr, pWC->pParse);
whereClauseInit(&sOr, pWC->pParse, pMaskSet);
whereSplit(&sOr, pExpr, TK_OR);
exprAnalyzeAll(pSrc, pMaskSet, &sOr);
exprAnalyzeAll(pSrc, &sOr);
assert( sOr.nTerm>0 );
j = 0;
do{
@@ -750,7 +755,7 @@ static void exprAnalyze(
transferJoinMarkings(pNew, pExpr);
pNew->pList = pList;
idxNew = whereClauseInsert(pWC, pNew, TERM_VIRTUAL|TERM_DYNAMIC);
exprAnalyze(pSrc, pMaskSet, pWC, idxNew);
exprAnalyze(pSrc, pWC, idxNew);
pTerm = &pWC->a[idxTerm];
pWC->a[idxNew].iParent = idxTerm;
pTerm->nChild = 1;
@@ -787,10 +792,10 @@ or_not_possible:
}
pNewExpr1 = sqlite3Expr(TK_GE, sqlite3ExprDup(pLeft), pStr1, 0);
idxNew1 = whereClauseInsert(pWC, pNewExpr1, TERM_VIRTUAL|TERM_DYNAMIC);
exprAnalyze(pSrc, pMaskSet, pWC, idxNew1);
exprAnalyze(pSrc, pWC, idxNew1);
pNewExpr2 = sqlite3Expr(TK_LT, sqlite3ExprDup(pLeft), pStr2, 0);
idxNew2 = whereClauseInsert(pWC, pNewExpr2, TERM_VIRTUAL|TERM_DYNAMIC);
exprAnalyze(pSrc, pMaskSet, pWC, idxNew2);
exprAnalyze(pSrc, pWC, idxNew2);
pTerm = &pWC->a[idxTerm];
if( isComplete ){
pWC->a[idxNew1].iParent = idxTerm;
@@ -836,6 +841,25 @@ or_not_possible:
#endif /* SQLITE_OMIT_VIRTUALTABLE */
}
/*
** Return TRUE if any of the expressions in pList->a[iFirst...] contain
** a reference to any table other than the iBase table.
*/
static int referencesOtherTables(
ExprList *pList, /* Search expressions in ths list */
ExprMaskSet *pMaskSet, /* Mapping from tables to bitmaps */
int iFirst, /* Be searching with the iFirst-th expression */
int iBase /* Ignore references to this table */
){
Bitmask allowed = ~getMask(pMaskSet, iBase);
while( iFirst<pList->nExpr ){
if( (exprTableUsage(pMaskSet, pList->a[iFirst++].pExpr)&allowed)!=0 ){
return 1;
}
}
return 0;
}
/*
** This routine decides if pIdx can be used to satisfy the ORDER BY
@@ -858,6 +882,7 @@ or_not_possible:
*/
static int isSortingIndex(
Parse *pParse, /* Parsing context */
ExprMaskSet *pMaskSet, /* Mapping from table indices to bitmaps */
Index *pIdx, /* The index we are testing */
int base, /* Cursor number for the table to be sorted */
ExprList *pOrderBy, /* The ORDER BY clause */
@@ -894,7 +919,7 @@ static int isSortingIndex(
if( pExpr->op!=TK_COLUMN || pExpr->iTable!=base ){
/* Can not use an index sort on anything that is not a column in the
** left-most table of the FROM clause */
return 0;
break;
}
pColl = sqlite3ExprCollSeq(pParse, pExpr);
if( !pColl ){
@@ -941,11 +966,12 @@ static int isSortingIndex(
}
j++;
pTerm++;
if( iColumn<0 ){
if( iColumn<0 && !referencesOtherTables(pOrderBy, pMaskSet, j, base) ){
/* If the indexed column is the primary key and everything matches
** so far, then we are assured that the index can be used to sort
** because the primary key is unique and so none of the other columns
** will make any difference
** so far and none of the ORDER BY terms to the right reference other
** tables in the join, then we are assured that the index can be used
** to sort because the primary key is unique and so none of the other
** columns will make any difference
*/
j = nTerm;
}
@@ -957,9 +983,12 @@ static int isSortingIndex(
** this index can be used for sorting. */
return 1;
}
if( j==pIdx->nColumn && pIdx->onError!=OE_None ){
if( pIdx->onError!=OE_None && i==pIdx->nColumn
&& !referencesOtherTables(pOrderBy, pMaskSet, j, base) ){
/* All terms of this index match some prefix of the ORDER BY clause
** and this index is UNIQUE, so this index can be used for sorting. */
** and the index is UNIQUE and no terms on the tail of the ORDER BY
** clause reference other tables in a join. If this is all true then
** the order by clause is superfluous. */
return 1;
}
return 0;
@@ -973,6 +1002,7 @@ static int isSortingIndex(
static int sortableByRowid(
int base, /* Cursor number for table to be sorted */
ExprList *pOrderBy, /* The ORDER BY clause */
ExprMaskSet *pMaskSet, /* Mapping from tables to bitmaps */
int *pbRev /* Set to 1 if ORDER BY is DESC */
){
Expr *p;
@@ -980,7 +1010,8 @@ static int sortableByRowid(
assert( pOrderBy!=0 );
assert( pOrderBy->nExpr>0 );
p = pOrderBy->a[0].pExpr;
if( p->op==TK_COLUMN && p->iTable==base && p->iColumn==-1 ){
if( p->op==TK_COLUMN && p->iTable==base && p->iColumn==-1
&& !referencesOtherTables(pOrderBy, pMaskSet, 1, base) ){
*pbRev = pOrderBy->a[0].sortOrder;
return 1;
}
@@ -1298,7 +1329,7 @@ static double bestIndex(
*/
if( pProbe==0 &&
findTerm(pWC, iCur, -1, 0, WO_EQ|WO_IN|WO_LT|WO_LE|WO_GT|WO_GE,0)==0 &&
(pOrderBy==0 || !sortableByRowid(iCur, pOrderBy, &rev)) ){
(pOrderBy==0 || !sortableByRowid(iCur, pOrderBy, pWC->pMaskSet, &rev)) ){
*pFlags = 0;
*ppIndex = 0;
*pnEq = 0;
@@ -1360,7 +1391,7 @@ static double bestIndex(
/* If the table scan does not satisfy the ORDER BY clause, increase
** the cost by NlogN to cover the expense of sorting. */
if( pOrderBy ){
if( sortableByRowid(iCur, pOrderBy, &rev) ){
if( sortableByRowid(iCur, pOrderBy, pWC->pMaskSet, &rev) ){
flags |= WHERE_ORDERBY|WHERE_ROWID_RANGE;
if( rev ){
flags |= WHERE_REVERSE;
@@ -1444,7 +1475,7 @@ static double bestIndex(
*/
if( pOrderBy ){
if( (flags & WHERE_COLUMN_IN)==0 &&
isSortingIndex(pParse,pProbe,iCur,pOrderBy,nEq,&rev) ){
isSortingIndex(pParse,pWC->pMaskSet,pProbe,iCur,pOrderBy,nEq,&rev) ){
if( flags==0 ){
flags = WHERE_COLUMN_RANGE;
}
@@ -1832,7 +1863,7 @@ WhereInfo *sqlite3WhereBegin(
** subexpression is separated by an AND operator.
*/
initMaskSet(&maskSet);
whereClauseInit(&wc, pParse);
whereClauseInit(&wc, pParse, &maskSet);
whereSplit(&wc, pWhere, TK_AND);
/* Allocate and initialize the WhereInfo structure that will become the
@@ -1863,7 +1894,7 @@ WhereInfo *sqlite3WhereBegin(
for(i=0; i<pTabList->nSrc; i++){
createMask(&maskSet, pTabList->a[i].iCursor);
}
exprAnalyzeAll(pTabList, &maskSet, &wc);
exprAnalyzeAll(pTabList, &wc);
if( sqlite3MallocFailed() ){
goto whereBeginNoMem;
}