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When flattening UNION ALL subqueries into a join query, ensure that separate cursor numbers are used for each segment of the newly flattened query.

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FossilOrigin-Name: c510377b0b052e400f2ee4f20220b61cdf74ee44b9bb9e6490787c88dd4c55aa
This commit is contained in:
dan
2020-12-18 16:13:39 +00:00
parent 9353beaff1
commit 964fa26e0c
5 changed files with 135 additions and 15 deletions
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97
src/select.c
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@@ -3649,6 +3649,86 @@ static void recomputeColumnsUsed(
}
#endif /* !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW) */
#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
/*
** Assign new cursor numbers to each of the items in pSrc. For each
** new cursor number assigned, set an entry in the aCsrMap[] array
** to map the old cursor number to the new:
**
** aCsrMap[iOld] = iNew;
**
** The array is guaranteed by the caller to be large enough for all
** existing cursor numbers in pSrc.
**
** If pSrc contains any sub-selects, call this routine recursively
** on the FROM clause of each such sub-select, with iExcept set to -1.
*/
static void srclistRenumberCursors(
Parse *pParse, /* Parse context */
int *aCsrMap, /* Array to store cursor mappings in */
SrcList *pSrc, /* FROM clause to renumber */
int iExcept /* FROM clause item to skip */
){
int i;
struct SrcList_item *pItem;
for(i=0, pItem=pSrc->a; i<pSrc->nSrc; i++, pItem++){
if( i!=iExcept ){
int iNew = pParse->nTab++;
aCsrMap[pItem->iCursor] = iNew;
pItem->iCursor = iNew;
if( pItem->pSelect ){
srclistRenumberCursors(pParse, aCsrMap, pItem->pSelect->pSrc, -1);
}
}
}
}
/*
** Expression walker callback used by renumberCursors() to update
** Expr objects to match newly assigned cursor numbers.
*/
static int renumberCursorsCb(Walker *pWalker, Expr *pExpr){
int *aCsrMap = pWalker->u.aiCol;
if( pExpr->op==TK_COLUMN && aCsrMap[pExpr->iTable] ){
pExpr->iTable = aCsrMap[pExpr->iTable];
}
return WRC_Continue;
}
/*
** Assign a new cursor number to each cursor in the FROM clause (Select.pSrc)
** of the SELECT statement passed as the second argument, and to each
** cursor in the FROM clause of any FROM clause sub-selects, recursively.
** Except, do not assign a new cursor number to the iExcept'th element in
** the FROM clause of (*p). Update all expressions and other references
** to refer to the new cursor numbers.
**
** Argument aCsrMap is an array that may be used for temporary working
** space. Two guarantees are made by the caller:
**
** * the array is larger than the largest cursor number used within the
** select statement passed as an argument, and
**
** * the array entries for all cursor numbers that do *not* appear in
** FROM clauses of the select statement as described above are
** initialized to zero.
*/
static void renumberCursors(
Parse *pParse, /* Parse context */
Select *p, /* Select to renumber cursors within */
int iExcept, /* FROM clause item to skip */
int *aCsrMap /* Working space */
){
Walker w;
srclistRenumberCursors(pParse, aCsrMap, p->pSrc, iExcept);
memset(&w, 0, sizeof(w));
w.u.aiCol = aCsrMap;
w.xExprCallback = renumberCursorsCb;
w.xSelectCallback = sqlite3SelectWalkNoop;
sqlite3WalkSelect(&w, p);
}
#endif /* !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW) */
#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
/*
** This routine attempts to flatten subqueries as a performance optimization.
@@ -3824,6 +3904,7 @@ static int flattenSubquery(
struct SrcList_item *pSubitem; /* The subquery */
sqlite3 *db = pParse->db;
Walker w; /* Walker to persist agginfo data */
int *aCsrMap = 0;
/* Check to see if flattening is permitted. Return 0 if not.
*/
@@ -3950,6 +4031,10 @@ static int flattenSubquery(
/* Restriction (23) */
if( (p->selFlags & SF_Recursive) ) return 0;
if( pSrc->nSrc>1 ){
aCsrMap = sqlite3DbMallocZero(db, pParse->nTab*sizeof(int));
}
}
/***** If we reach this point, flattening is permitted. *****/
@@ -4024,6 +4109,9 @@ static int flattenSubquery(
if( pNew==0 ){
p->pPrior = pPrior;
}else{
if( aCsrMap && db->mallocFailed==0 ){
renumberCursors(pParse, pNew, iFrom, aCsrMap);
}
pNew->pPrior = pPrior;
if( pPrior ) pPrior->pNext = pNew;
pNew->pNext = p;
@@ -4032,10 +4120,11 @@ static int flattenSubquery(
" creates %u as peer\n",pNew->selId));
}
assert( pSubitem->pSelect==0 );
if( db->mallocFailed ){
pSubitem->pSelect = pSub1;
return 1;
}
}
sqlite3DbFree(db, aCsrMap);
if( db->mallocFailed ){
pSubitem->pSelect = pSub1;
return 1;
}
/* Defer deleting the Table object associated with the