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Allow sub-queries that use UNION ALL to be flattened, even if the parent query is a join. Still some problems on this branch.

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FossilOrigin-Name: 00e4bf74d3dfb87666a2266905f7d1a2afc6eb088d22cfd4f38f048733d6b936
This commit is contained in:
dan
2020-12-16 20:00:46 +00:00
parent e5baf5c283
commit de9ed6293d
7 changed files with 146 additions and 58 deletions
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64
src/select.c
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@@ -3920,7 +3920,7 @@ static int flattenSubquery(
if( pSub->pOrderBy ){
return 0; /* Restriction (20) */
}
if( isAgg || (p->selFlags & SF_Distinct)!=0 || pSrc->nSrc!=1 ){
if( isAgg || (p->selFlags & SF_Distinct)!=0 || isLeftJoin>0 ){
return 0; /* (17d1), (17d2), or (17d3) */
}
for(pSub1=pSub; pSub1; pSub1=pSub1->pPrior){
@@ -3947,15 +3947,10 @@ static int flattenSubquery(
if( p->pOrderBy->a[ii].u.x.iOrderByCol==0 ) return 0;
}
}
}
/* Ex-restriction (23):
** The only way that the recursive part of a CTE can contain a compound
** subquery is for the subquery to be one term of a join. But if the
** subquery is a join, then the flattening has already been stopped by
** restriction (17d3)
*/
assert( (p->selFlags & SF_Recursive)==0 || pSub->pPrior==0 );
/* Restriction (23) */
if( (p->selFlags & SF_Recursive) ) return 0;
}
/***** If we reach this point, flattening is permitted. *****/
SELECTTRACE(1,pParse,p,("flatten %u.%p from term %d\n",
@@ -3967,6 +3962,17 @@ static int flattenSubquery(
testcase( i==SQLITE_DENY );
pParse->zAuthContext = zSavedAuthContext;
/* Delete the transient structures associated with thesubquery */
pSub1 = pSubitem->pSelect;
sqlite3DbFree(db, pSubitem->zDatabase);
sqlite3DbFree(db, pSubitem->zName);
sqlite3DbFree(db, pSubitem->zAlias);
pSubitem->zDatabase = 0;
pSubitem->zName = 0;
pSubitem->zAlias = 0;
pSubitem->pSelect = 0;
assert( pSubitem->pOn==0 );
/* If the sub-query is a compound SELECT statement, then (by restrictions
** 17 and 18 above) it must be a UNION ALL and the parent query must
** be of the form:
@@ -4005,15 +4011,16 @@ static int flattenSubquery(
ExprList *pOrderBy = p->pOrderBy;
Expr *pLimit = p->pLimit;
Select *pPrior = p->pPrior;
Table *pItemTab = pSubitem->pTab;
pSubitem->pTab = 0;
p->pOrderBy = 0;
p->pSrc = 0;
p->pPrior = 0;
p->pLimit = 0;
pNew = sqlite3SelectDup(db, p, 0);
p->pLimit = pLimit;
p->pOrderBy = pOrderBy;
p->pSrc = pSrc;
p->op = TK_ALL;
pSubitem->pTab = pItemTab;
if( pNew==0 ){
p->pPrior = pPrior;
}else{
@@ -4024,25 +4031,13 @@ static int flattenSubquery(
SELECTTRACE(2,pParse,p,("compound-subquery flattener"
" creates %u as peer\n",pNew->selId));
}
if( db->mallocFailed ) return 1;
assert( pSubitem->pSelect==0 );
if( db->mallocFailed ){
pSubitem->pSelect = pSub1;
return 1;
}
}
/* Begin flattening the iFrom-th entry of the FROM clause
** in the outer query.
*/
pSub = pSub1 = pSubitem->pSelect;
/* Delete the transient table structure associated with the
** subquery
*/
sqlite3DbFree(db, pSubitem->zDatabase);
sqlite3DbFree(db, pSubitem->zName);
sqlite3DbFree(db, pSubitem->zAlias);
pSubitem->zDatabase = 0;
pSubitem->zName = 0;
pSubitem->zAlias = 0;
pSubitem->pSelect = 0;
/* Defer deleting the Table object associated with the
** subquery until code generation is
** complete, since there may still exist Expr.pTab entries that
@@ -4075,6 +4070,7 @@ static int flattenSubquery(
** those references with expressions that resolve to the subquery FROM
** elements we are now copying in.
*/
pSub = pSub1;
for(pParent=p; pParent; pParent=pParent->pPrior, pSub=pSub->pPrior){
int nSubSrc;
u8 jointype = 0;
@@ -4083,16 +4079,10 @@ static int flattenSubquery(
nSubSrc = pSubSrc->nSrc; /* Number of terms in subquery FROM clause */
pSrc = pParent->pSrc; /* FROM clause of the outer query */
if( pSrc ){
assert( pParent==p ); /* First time through the loop */
jointype = pSubitem->fg.jointype;
}else{
assert( pParent!=p ); /* 2nd and subsequent times through the loop */
pSrc = sqlite3SrcListAppend(pParse, 0, 0, 0);
if( pSrc==0 ) break;
pParent->pSrc = pSrc;
if( pParent==p ){
jointype = pSubitem->fg.jointype; /* First time through the loop */
}
/* The subquery uses a single slot of the FROM clause of the outer
** query. If the subquery has more than one element in its FROM clause,
** then expand the outer query to make space for it to hold all elements