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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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25
src/resolve.c
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@@ -570,6 +570,18 @@ static void notValidCheckConstraint(
# define notValidCheckConstraint(P,N,M)
#endif
/*
** Expression p should encode a floating point value between 1.0 and 0.0.
** Return 1024 times this value. Or return -1 if p is not a floating point
** value between 1.0 and 0.0.
*/
static int exprProbability(Expr *p){
double r = -1.0;
if( p->op!=TK_FLOAT ) return -1;
sqlite3AtoF(p->u.zToken, &r, sqlite3Strlen30(p->u.zToken), SQLITE_UTF8);
if( r<0.0 || r>1.0 ) return -1;
return (int)(r*1000.0);
}
/*
** This routine is callback for sqlite3WalkExpr().
@@ -683,6 +695,19 @@ static int resolveExprStep(Walker *pWalker, Expr *pExpr){
}
}else{
is_agg = pDef->xFunc==0;
if( pDef->funcFlags & SQLITE_FUNC_UNLIKELY ){
ExprSetProperty(pExpr, EP_Hint);
if( n==2 ){
pExpr->iTable = exprProbability(pList->a[1].pExpr);
if( pExpr->iTable<0 ){
sqlite3ErrorMsg(pParse, "second parameter to unlikely() must be "
"between 0.0 and 1.0");
pNC->nErr++;
}
}else{
pExpr->iTable = 100;
}
}
}
#ifndef SQLITE_OMIT_AUTHORIZATION
if( pDef ){