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Avoid generating hints using constraints that are also used to initialize the

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cursor, since presumably the cursor already knows about those constraints.

FossilOrigin-Name: 142b048ac778620dd4e448c2e969982eb8188501
This commit is contained in:
drh
2015-08-17 17:19:28 +00:00
parent a67a31624d
commit b413a5467a
4 changed files with 68 additions and 21 deletions
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31
src/wherecode.c
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@@ -669,8 +669,9 @@ static int codeCursorHintFixExpr(Walker *pWalker, Expr *pExpr){
** Insert an OP_CursorHint instruction if it is appropriate to do so.
*/
static void codeCursorHint(
WhereInfo *pWInfo,
WhereLevel *pLevel
WhereInfo *pWInfo, /* The where clause */
WhereLevel *pLevel, /* Which loop to provide hints for */
WhereTerm *pEndRange /* Hint this end-of-scan boundary term if not NULL */
){
Parse *pParse = pWInfo->pParse;
sqlite3 *db = pParse->db;
@@ -680,7 +681,8 @@ static void codeCursorHint(
int iCur;
WhereClause *pWC;
WhereTerm *pTerm;
int i;
WhereLoop *pWLoop;
int i, j;
struct CCurHint sHint;
Walker sWalker;
@@ -694,18 +696,33 @@ static void codeCursorHint(
sWalker.pParse = pParse;
sWalker.u.pCCurHint = &sHint;
pWC = &pWInfo->sWC;
pWLoop = pLevel->pWLoop;
for(i=0; i<pWC->nTerm; i++){
pTerm = &pWC->a[i];
if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
if( pTerm->prereqAll & pLevel->notReady ) continue;
if( ExprHasProperty(pTerm->pExpr, EP_FromJoin) ) continue;
/* All terms in pWLoop->aLTerm[] except pEndRange are used to initialize
** the cursor. No need to hint initialization terms. */
if( pTerm!=pEndRange ){
for(j=0; j<pWLoop->nLTerm && pWLoop->aLTerm[j]!=pTerm; j++){}
if( j<pWLoop->nLTerm ) continue;
}
/* No subqueries or non-deterministic functions allowed */
if( sqlite3ExprContainsSubquery(pTerm->pExpr) ) continue;
/* For an index scan, make sure referenced columns are actually in
** the index. */
if( sHint.pIdx!=0 ){
sWalker.eCode = 0;
sWalker.xExprCallback = codeCursorHintCheckExpr;
sqlite3WalkExpr(&sWalker, pTerm->pExpr);
if( sWalker.eCode ) continue;
}
/* If we survive all prior tests, that means this term is worth hinting */
pExpr = sqlite3ExprAnd(db, pExpr, sqlite3ExprDup(db, pTerm->pExpr, 0));
}
if( pExpr!=0 ){
@@ -717,7 +734,7 @@ static void codeCursorHint(
}
}
#else
# define codeCursorHint(A,B) /* No-op */
# define codeCursorHint(A,B,C) /* No-op */
#endif /* SQLITE_ENABLE_CURSOR_HINTS */
/*
@@ -883,7 +900,7 @@ Bitmask sqlite3WhereCodeOneLoopStart(
pStart = pEnd;
pEnd = pTerm;
}
codeCursorHint(pWInfo, pLevel);
codeCursorHint(pWInfo, pLevel, pEnd);
if( pStart ){
Expr *pX; /* The expression that defines the start bound */
int r1, rTemp; /* Registers for holding the start boundary */
@@ -1106,7 +1123,7 @@ Bitmask sqlite3WhereCodeOneLoopStart(
start_constraints = pRangeStart || nEq>0;
/* Seek the index cursor to the start of the range. */
codeCursorHint(pWInfo, pLevel);
codeCursorHint(pWInfo, pLevel, pRangeEnd);
nConstraint = nEq;
if( pRangeStart ){
Expr *pRight = pRangeStart->pExpr->pRight;
@@ -1534,7 +1551,7 @@ Bitmask sqlite3WhereCodeOneLoopStart(
** a pseudo-cursor. No need to Rewind or Next such cursors. */
pLevel->op = OP_Noop;
}else{
codeCursorHint(pWInfo, pLevel);
codeCursorHint(pWInfo, pLevel, 0);
pLevel->op = aStep[bRev];
pLevel->p1 = iCur;
pLevel->p2 = 1 + sqlite3VdbeAddOp2(v, aStart[bRev], iCur, addrBrk);