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Make sure the ORDER BY collating sequences are compatible with the

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comparison collations before using the merge algorithm for compound
SELECT statements.  Candidate fix for ticket [6709574d2a8d8].

FossilOrigin-Name: fc3630cdef6e2cdbfb4e7b373d1a094753e55016
This commit is contained in:
drh
2013-05-07 17:49:08 +00:00
parent e8dee7d1ed
commit c01b7306ae
5 changed files with 184 additions and 20 deletions
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67
src/select.c
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@@ -3260,6 +3260,69 @@ int sqlite3IndexedByLookup(Parse *pParse, struct SrcList_item *pFrom){
}
return SQLITE_OK;
}
/*
** Detect compound SELECT statements that use an ORDER BY clause with
** an alternative collating sequence.
**
** SELECT ... FROM t1 EXCEPT SELECT ... FROM t2 ORDER BY .. COLLATE ...
**
** These are rewritten as a subquery:
**
** SELECT * FROM (SELECT ... FROM t1 EXCEPT SELECT ... FROM t2)
** ORDER BY ... COLLATE ...
**
** This transformation is necessary because the multiSelectOrderBy() routine
** above that generates the code for a compound SELECT with an ORDER BY clause
** uses a merge algorithm that requires the same collating sequence on the
** result columns as on the ORDER BY clause. See ticket
** http://www.sqlite.org/src/info/6709574d2a
**
** This transformation is only needed for EXCEPT, INTERSECT, and UNION.
** The UNION ALL operator works fine with multiSelectOrderBy() even when
** there are COLLATE terms in the ORDER BY.
*/
static int convertCompoundSelectToSubquery(Walker *pWalker, Select *p){
int i;
Select *pNew;
Select *pX;
sqlite3 *db;
struct ExprList_item *a;
SrcList *pNewSrc;
Parse *pParse;
Token dummy;
if( p->pPrior==0 ) return WRC_Continue;
if( p->pOrderBy==0 ) return WRC_Continue;
for(pX=p; pX && (pX->op==TK_ALL || pX->op==TK_SELECT); pX=pX->pPrior){}
if( pX==0 ) return WRC_Continue;
a = p->pOrderBy->a;
for(i=p->pOrderBy->nExpr-1; i>=0; i--){
if( a[i].pExpr->flags & EP_Collate ) break;
}
if( i<0 ) return WRC_Continue;
/* If we reach this point, that means the transformation is required. */
pParse = pWalker->pParse;
db = pParse->db;
pNew = sqlite3DbMallocZero(db, sizeof(*pNew) );
if( pNew==0 ) return WRC_Abort;
memset(&dummy, 0, sizeof(dummy));
pNewSrc = sqlite3SrcListAppendFromTerm(pParse,0,0,0,&dummy,pNew,0,0);
if( pNewSrc==0 ) return WRC_Abort;
*pNew = *p;
p->pSrc = pNewSrc;
p->pEList = sqlite3ExprListAppend(pParse, 0, sqlite3Expr(db, TK_ALL, 0));
p->op = TK_SELECT;
p->pWhere = 0;
pNew->pGroupBy = 0;
pNew->pHaving = 0;
pNew->pOrderBy = 0;
p->pPrior = 0;
pNew->pLimit = 0;
pNew->pOffset = 0;
return WRC_Continue;
}
/*
** This routine is a Walker callback for "expanding" a SELECT statement.
@@ -3577,10 +3640,12 @@ static int exprWalkNoop(Walker *NotUsed, Expr *NotUsed2){
static void sqlite3SelectExpand(Parse *pParse, Select *pSelect){
Walker w;
memset(&w, 0, sizeof(w));
w.xSelectCallback = selectExpander;
w.xSelectCallback = convertCompoundSelectToSubquery;
w.xExprCallback = exprWalkNoop;
w.pParse = pParse;
sqlite3WalkSelect(&w, pSelect);
w.xSelectCallback = selectExpander;
sqlite3WalkSelect(&w, pSelect);
}