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Initial implementation of the unlikely() SQL function used as a hint to

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the query planner.

FossilOrigin-Name: 036fc37a034093a4c6fc190633bd41c2b7230d77
This commit is contained in:
drh
2013-09-06 15:23:29 +00:00
parent d36e104112
commit cca9f3d291
8 changed files with 118 additions and 31 deletions
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20
src/expr.c
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@@ -89,8 +89,16 @@ Expr *sqlite3ExprAddCollateString(Parse *pParse, Expr *pExpr, const char *zC){
** an expression.
*/
Expr *sqlite3ExprSkipCollate(Expr *pExpr){
while( pExpr && (pExpr->op==TK_COLLATE || pExpr->op==TK_AS) ){
pExpr = pExpr->pLeft;
while( pExpr ){
if( pExpr->op==TK_COLLATE || pExpr->op==TK_AS ){
pExpr = pExpr->pLeft;
}else if( ExprHasAnyProperty(pExpr, EP_Hint) ){
assert( !ExprHasProperty(pExpr, EP_xIsSelect) );
assert( pExpr->x.pList->nExpr>0 );
pExpr = pExpr->x.pList->a[0].pExpr;
}else{
break;
}
}
return pExpr;
}
@@ -2649,6 +2657,14 @@ int sqlite3ExprCodeTarget(Parse *pParse, Expr *pExpr, int target){
break;
}
/* The UNLIKELY() function is a no-op. The result is the value
** of the first argument.
*/
if( pDef->funcFlags & SQLITE_FUNC_UNLIKELY ){
assert( nFarg>=1 );
sqlite3ExprCode(pParse, pFarg->a[0].pExpr, target);
break;
}
if( pFarg ){
r1 = sqlite3GetTempRange(pParse, nFarg);