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Allow only a single recursive reference in a recursive CTE. Also require that this reference is not part of a sub-query.

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FossilOrigin-Name: a296b73360d34c9364eceb2cc09a9a92adc4abb8
This commit is contained in:
dan
2014-01-16 18:34:33 +00:00
parent 8290c2ad5a
commit eae73fbfb9
7 changed files with 62 additions and 85 deletions
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88
src/select.c
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@@ -1744,7 +1744,7 @@ static int multiSelect(
** the last (right-most) SELECT in the series may have an ORDER BY or LIMIT.
*/
assert( p && p->pPrior ); /* Calling function guarantees this much */
assert( p->pRecurse==0 || p->op==TK_ALL || p->op==TK_UNION );
assert( (p->selFlags & SF_Recursive)==0 || p->op==TK_ALL || p->op==TK_UNION );
db = pParse->db;
pPrior = p->pPrior;
assert( pPrior->pRightmost!=pPrior );
@@ -1794,27 +1794,36 @@ static int multiSelect(
/* If this is a recursive query, check that there is no ORDER BY or
** LIMIT clause. Neither of these are supported. */
assert( p->pOffset==0 || p->pLimit );
if( p->pRecurse && (p->pOrderBy || p->pLimit) ){
if( (p->selFlags & SF_Recursive) && (p->pOrderBy || p->pLimit) ){
sqlite3ErrorMsg(pParse, "%s in a recursive query is not allowed",
p->pOrderBy ? "ORDER BY" : "LIMIT"
);
goto multi_select_end;
}
if( p->pRecurse ){
if( p->selFlags & SF_Recursive ){
SrcList *pSrc = p->pSrc;
int nCol = p->pEList->nExpr;
int addrNext;
int addrSwap;
int iCont, iBreak;
int tmp1, tmp2; /* Cursors used to access temporary tables */
int tmp1; /* Intermediate table */
int tmp2; /* Next intermediate table */
int tmp3 = 0; /* To ensure unique results if UNION */
int eDest = SRT_Table;
SelectDest tmp2dest;
int i;
iBreak = sqlite3VdbeMakeLabel(v);
iCont = sqlite3VdbeMakeLabel(v);
tmp1 = pParse->nTab++;
for(i=0; ALWAYS(i<pSrc->nSrc); i++){
if( pSrc->a[i].isRecursive ){
tmp1 = pSrc->a[i].iCursor;
break;
}
}
tmp2 = pParse->nTab++;
if( p->op==TK_UNION ){
eDest = SRT_DistTable;
@@ -1848,11 +1857,7 @@ static int multiSelect(
** SELECT is running, the contents of tmp1 are read by recursive
** references to the current CTE. */
p->pPrior = 0;
p->pRecurse->tnum = tmp1;
assert( (p->pRecurse->tabFlags & TF_Recursive)==0 );
p->pRecurse->tabFlags |= TF_Recursive;
rc = sqlite3Select(pParse, p, &tmp2dest);
p->pRecurse->tabFlags &= ~TF_Recursive;
assert( p->pPrior==0 );
p->pPrior = pPrior;
if( rc ) goto multi_select_end;
@@ -3009,8 +3014,8 @@ static int flattenSubquery(
if( pSub->pLimit && (p->selFlags & SF_Distinct)!=0 ){
return 0; /* Restriction (21) */
}
if( pSub->pRecurse ) return 0; /* Restriction (22) */
if( p->pRecurse && pSub->pPrior ) return 0; /* Restriction (23) */
if( pSub->selFlags & SF_Recursive ) return 0; /* Restriction (22) */
if( (p->selFlags & SF_Recursive) && pSub->pPrior ) return 0; /* (23) */
/* OBSOLETE COMMENT 1:
** Restriction 3: If the subquery is a join, make sure the subquery is
@@ -3593,19 +3598,10 @@ static int withExpand(
assert( pFrom->pTab==0 );
pCte = searchWith(pParse->pWith, pFrom);
if( pCte==0 ){
/* no-op */
}else if( pCte==pParse->pCte && (pTab = pCte->pTab) ){
/* This is the recursive part of a recursive CTE */
assert( pFrom->pTab==0 && pFrom->isRecursive==0 && pFrom->pSelect==0 );
pFrom->pTab = pTab;
pFrom->isRecursive = 1;
pTab->nRef++;
}else{
if( pCte ){
ExprList *pEList;
Select *pSel;
Select *pLeft; /* Left-most SELECT statement */
int bRecursive;
pFrom->pTab = pTab = sqlite3DbMallocZero(db, sizeof(Table));
if( pTab==0 ) return WRC_Abort;
@@ -3618,16 +3614,37 @@ static int withExpand(
if( db->mallocFailed ) return SQLITE_NOMEM;
assert( pFrom->pSelect );
if( ctePush(pParse, pCte) ) return WRC_Abort;
/* Check if this is a recursive CTE. */
pSel = pFrom->pSelect;
bRecursive = (pSel->op==TK_ALL || pSel->op==TK_UNION);
if( bRecursive ){
assert( pSel->pPrior );
sqlite3WalkSelect(pWalker, pSel->pPrior);
}else{
sqlite3WalkSelect(pWalker, pSel);
if( pSel->op==TK_ALL || pSel->op==TK_UNION ){
int i;
SrcList *pSrc = pFrom->pSelect->pSrc;
for(i=0; i<pSrc->nSrc; i++){
struct SrcList_item *pItem = &pSrc->a[i];
if( pItem->zDatabase==0
&& pItem->zName!=0
&& 0==sqlite3StrICmp(pItem->zName, pCte->zName)
){
pItem->pTab = pTab;
pItem->isRecursive = 1;
pTab->nRef++;
pSel->selFlags |= SF_Recursive;
}
}
}
/* Only one recursive reference is permitted. */
if( pTab->nRef>2 ){
sqlite3ErrorMsg(
pParse, "multiple recursive references in cte: %s", pCte->zName
);
return WRC_Abort;
}
assert( pTab->nRef==1 || ((pSel->selFlags&SF_Recursive) && pTab->nRef==2 ));
if( ctePush(pParse, pCte) ) return WRC_Abort;
sqlite3WalkSelect(pWalker, pTab->nRef==2 ? pSel->pPrior : pSel);
for(pLeft=pSel; pLeft->pPrior; pLeft=pLeft->pPrior);
pEList = pLeft->pEList;
if( pCte->pCols ){
@@ -3639,20 +3656,9 @@ static int withExpand(
}
pEList = pCte->pCols;
}
selectColumnsFromExprList(pParse, pEList, &pTab->nCol, &pTab->aCol);
if( bRecursive ){
int nRef = pTab->nRef;
pCte->pTab = pTab;
sqlite3WalkSelect(pWalker, pSel);
pCte->pTab = 0;
if( pTab->nRef > nRef){
pSel->pRecurse = pTab;
assert( pTab->tnum==0 );
}
}
if( pSel->selFlags & SF_Recursive ) sqlite3WalkSelect(pWalker, pSel);
ctePop(pParse, pCte);
}
@@ -3715,6 +3721,8 @@ static int selectExpander(Walker *pWalker, Select *p){
*/
for(i=0, pFrom=pTabList->a; i<pTabList->nSrc; i++, pFrom++){
Table *pTab;
assert( pFrom->isRecursive==0 || pFrom->pTab );
if( pFrom->isRecursive ) continue;
if( pFrom->pTab!=0 ){
/* This statement has already been prepared. There is no need
** to go further. */