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Remove a redundant restriction from the query flattener.

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FossilOrigin-Name: 66629b2a0997ceedcfb38553f2200466b6c4e352ea00f8a0a7cb67a660c19523
This commit is contained in:
drh
2017-10-04 05:59:54 +00:00
parent e76acc654f
commit cdb2f60743
3 changed files with 18 additions and 12 deletions
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16
src/select.c
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@@ -3393,8 +3393,9 @@ static void substSelect(
**
** (22) The subquery may not be a recursive CTE.
**
** (23) If the outer query is a recursive CTE, then the sub-query may not be
** a compound query. This restriction is because transforming the
** (**) Subsumed into restriction (17d3). Was: If the outer query is
** a recursive CTE, then the sub-query may not be a compound query.
** This restriction is because transforming the
** parent to a compound query confuses the code that handles
** recursive queries in multiSelect().
**
@@ -3475,9 +3476,6 @@ static int flattenSubquery(
if( pSub->selFlags & (SF_Recursive) ){
return 0; /* Restrictions (22) */
}
if( (p->selFlags & SF_Recursive) && pSub->pPrior ){
return 0; /* Restriction (23) */
}
/*
** If the subquery is the right operand of a LEFT JOIN, then the
@@ -3551,6 +3549,14 @@ static int flattenSubquery(
}
}
/* 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 );
/***** If we reach this point, flattening is permitted. *****/
SELECTTRACE(1,pParse,p,("flatten %s.%p from term %d\n",
pSub->zSelName, pSub, iFrom));