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Fix the cursor hint mechanism so that it does the right thing for indexed

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lookups.

FossilOrigin-Name: 581e3d4988e98975fea5daaeb9f854c54a4976b7
This commit is contained in:
drh
2015-08-14 18:50:04 +00:00
parent 0df57012da
commit 2f2b02785a
6 changed files with 91 additions and 34 deletions
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97
src/wherecode.c
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@@ -588,28 +588,70 @@ static void whereLikeOptimizationStringFixup(
}
#ifdef SQLITE_ENABLE_CURSOR_HINTS
/*
** Information is passed from codeCursorHint() down to individual nodes of
** the expression tree (by sqlite3WalkExpr()) using an instance of this
** structure.
*/
struct CCurHint {
int iTabCur; /* Cursor for the main table */
int iIdxCur; /* Cursor for the index, if pIdx!=0. Unused otherwise */
Index *pIdx; /* The index used to access the table */
};
/*
** This function is called for every node of an expression that is a candidate
** for a cursor hint on an index cursor. For TK_COLUMN nodes that reference
** the table CCurHint.iTabCur, verify that the same column can be
** accessed through the index. If it cannot, then set pWalker->eCode to 1.
*/
static int codeCursorHintCheckExpr(Walker *pWalker, Expr *pExpr){
struct CCurHint *pHint = pWalker->u.pCCurHint;
assert( pHint->pIdx!=0 );
if( pExpr->op==TK_COLUMN
&& pExpr->iTable==pHint->iTabCur
&& sqlite3ColumnOfIndex(pHint->pIdx, pExpr->iColumn)<0
){
pWalker->eCode = 1;
}
return WRC_Continue;
}
/*
** This function is called on every node of an expression tree used as an
** argument to the OP_CursorHint instruction. If the node is a TK_COLUMN
** that accesses any cursor other than (pWalker->u.n), do the following:
** that accesses any table other than the one identified by
** CCurHint.iTabCur, then do the following:
**
** 1) allocate a register and code an OP_Column instruction to read
** the specified column into the new register, and
**
** 2) transform the expression node to a TK_REGISTER node that reads
** from the newly populated register.
**
** Also, if the node is a TK_COLUMN that does access the table idenified
** by pCCurHint.iTabCur, and an index is being used (which we will
** know because CCurHint.pIdx!=0) then transform the TK_COLUMN into
** an access of the index rather than the original table.
*/
static int codeCursorHintFixExpr(Walker *pWalker, Expr *pExpr){
int rc = WRC_Continue;
if( pExpr->op==TK_COLUMN && pExpr->iTable!=pWalker->u.n ){
Vdbe *v = pWalker->pParse->pVdbe;
int reg = ++pWalker->pParse->nMem; /* Register for column value */
sqlite3ExprCodeGetColumnOfTable(
v, pExpr->pTab, pExpr->iTable, pExpr->iColumn, reg
);
pExpr->op = TK_REGISTER;
pExpr->iTable = reg;
struct CCurHint *pHint = pWalker->u.pCCurHint;
if( pExpr->op==TK_COLUMN ){
if( pExpr->iTable!=pHint->iTabCur ){
Vdbe *v = pWalker->pParse->pVdbe;
int reg = ++pWalker->pParse->nMem; /* Register for column value */
sqlite3ExprCodeGetColumnOfTable(
v, pExpr->pTab, pExpr->iTable, pExpr->iColumn, reg
);
pExpr->op = TK_REGISTER;
pExpr->iTable = reg;
}else if( pHint->pIdx!=0 ){
pExpr->iTable = pHint->iIdxCur;
pExpr->iColumn = sqlite3ColumnOfIndex(pHint->pIdx, pExpr->iColumn);
assert( pExpr->iColumn>=0 );
}
}else if( pExpr->op==TK_AGG_FUNCTION ){
/* An aggregate function in the WHERE clause of a query means this must
** be a correlated sub-query, and expression pExpr is an aggregate from
@@ -628,21 +670,29 @@ static int codeCursorHintFixExpr(Walker *pWalker, Expr *pExpr){
*/
static void codeCursorHint(
WhereInfo *pWInfo,
int iLevel
WhereLevel *pLevel
){
Parse *pParse = pWInfo->pParse;
sqlite3 *db = pParse->db;
Vdbe *v = pParse->pVdbe;
WhereLevel *pLevel;
Expr *pExpr = 0;
WhereLoop *pLoop = pLevel->pWLoop;
int iCur;
WhereClause *pWC;
WhereTerm *pTerm;
int i;
struct CCurHint sHint;
Walker sWalker;
if( OptimizationDisabled(db, SQLITE_CursorHints) ) return;
pLevel = &pWInfo->a[iLevel];
iCur = pWInfo->pTabList->a[pLevel->iFrom].iCursor;
iCur = pLevel->iTabCur;
assert( iCur==pWInfo->pTabList->a[pLevel->iFrom].iCursor );
sHint.iTabCur = iCur;
sHint.iIdxCur = pLevel->iIdxCur;
sHint.pIdx = pLoop->u.btree.pIndex;
memset(&sWalker, 0, sizeof(sWalker));
sWalker.pParse = pParse;
sWalker.u.pCCurHint = &sHint;
pWC = &pWInfo->sWC;
for(i=0; i<pWC->nTerm; i++){
pTerm = &pWC->a[i];
@@ -650,17 +700,20 @@ static void codeCursorHint(
if( pTerm->prereqAll & pLevel->notReady ) continue;
if( ExprHasProperty(pTerm->pExpr, EP_FromJoin) ) continue;
if( sqlite3ExprContainsSubquery(pTerm->pExpr) ) continue;
if( sHint.pIdx!=0 ){
sWalker.eCode = 0;
sWalker.xExprCallback = codeCursorHintCheckExpr;
sqlite3WalkExpr(&sWalker, pTerm->pExpr);
if( sWalker.eCode ) continue;
}
pExpr = sqlite3ExprAnd(db, pExpr, sqlite3ExprDup(db, pTerm->pExpr, 0));
}
if( pExpr!=0 ){
const char *a = (const char*)pExpr;
Walker sWalker;
memset(&sWalker, 0, sizeof(sWalker));
sWalker.xExprCallback = codeCursorHintFixExpr;
sWalker.pParse = pParse;
sWalker.u.n = pLevel->iTabCur;
sqlite3WalkExpr(&sWalker, pExpr);
sqlite3VdbeAddOp4(v, OP_CursorHint, pLevel->iTabCur, iCur, 0, a, P4_EXPR);
sqlite3VdbeAddOp4(v, OP_CursorHint,
(sHint.pIdx ? sHint.iIdxCur : sHint.iTabCur), 0, 0,
(const char*)pExpr, P4_EXPR);
}
}
#else
@@ -830,7 +883,7 @@ Bitmask sqlite3WhereCodeOneLoopStart(
pStart = pEnd;
pEnd = pTerm;
}
codeCursorHint(pWInfo, iLevel);
codeCursorHint(pWInfo, pLevel);
if( pStart ){
Expr *pX; /* The expression that defines the start bound */
int r1, rTemp; /* Registers for holding the start boundary */
@@ -1053,7 +1106,7 @@ Bitmask sqlite3WhereCodeOneLoopStart(
start_constraints = pRangeStart || nEq>0;
/* Seek the index cursor to the start of the range. */
codeCursorHint(pWInfo, iLevel);
codeCursorHint(pWInfo, pLevel);
nConstraint = nEq;
if( pRangeStart ){
Expr *pRight = pRangeStart->pExpr->pRight;
@@ -1481,7 +1534,7 @@ Bitmask sqlite3WhereCodeOneLoopStart(
** a pseudo-cursor. No need to Rewind or Next such cursors. */
pLevel->op = OP_Noop;
}else{
codeCursorHint(pWInfo, iLevel);
codeCursorHint(pWInfo, pLevel);
pLevel->op = aStep[bRev];
pLevel->p1 = iCur;
pLevel->p2 = 1 + sqlite3VdbeAddOp2(v, aStart[bRev], iCur, addrBrk);