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Remove an incorrect NEVER() reported at

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[forum:/forumpost/5bbabfb7ce|forum post 5bbabfb7ce].  Also use this
opportunity to improve the isSimpleCount() function with better formatting,
an expanded header comment, and some extra assert() and textcase() macros.

FossilOrigin-Name: 2927185be81a5aa0dce70dd06040d05c2816a4d18b5094a6f709732cfd6968dc
This commit is contained in:
drh
2021-11-05 11:52:33 +00:00
parent 11e29677a2
commit a1c4c3c187
3 changed files with 27 additions and 15 deletions
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26
src/select.c
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@@ -4948,7 +4948,13 @@ static u8 minMaxQuery(sqlite3 *db, Expr *pFunc, ExprList **ppMinMax){
**
** where table is a database table, not a sub-select or view. If the query
** does match this pattern, then a pointer to the Table object representing
** <tbl> is returned. Otherwise, 0 is returned.
** <tbl> is returned. Otherwise, NULL is returned.
**
** This routine a condition for the count optimization. A correct answer
** is obtained (though perhaps more slowly) if this routine returns NULL when
** it could have returned a table pointer. But returning the pointer when
** NULL should have been returned can result in incorrect answers and/or
** crashes. So, when in doubt, return NULL.
*/
static Table *isSimpleCount(Select *p, AggInfo *pAggInfo){
Table *pTab;
@@ -4956,19 +4962,25 @@ static Table *isSimpleCount(Select *p, AggInfo *pAggInfo){
assert( !p->pGroupBy );
if( p->pWhere || p->pEList->nExpr!=1
|| p->pSrc->nSrc!=1 || p->pSrc->a[0].pSelect
if( p->pWhere
|| p->pEList->nExpr!=1
|| p->pSrc->nSrc!=1
|| p->pSrc->a[0].pSelect
|| pAggInfo->nFunc!=1
){
return 0;
}
pTab = p->pSrc->a[0].pTab;
assert( pTab!=0 );
assert( !IsView(pTab) );
if( !IsOrdinaryTable(pTab) ) return 0;
pExpr = p->pEList->a[0].pExpr;
assert( pTab && !IsView(pTab) && pExpr );
if( IsVirtual(pTab) ) return 0;
assert( pExpr!=0 );
if( pExpr->op!=TK_AGG_FUNCTION ) return 0;
if( NEVER(pAggInfo->nFunc==0) ) return 0;
if( (pAggInfo->aFunc[0].pFunc->funcFlags&SQLITE_FUNC_COUNT)==0 ) return 0;
assert( pAggInfo->aFunc[0].pFExpr==pExpr );
testcase( ExprHasProperty(pExpr, EP_Distinct) );
testcase( ExprHasProperty(pExpr, EP_WinFunc) );
if( ExprHasProperty(pExpr, EP_Distinct|EP_WinFunc) ) return 0;
return pTab;