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Improve generated column names for cases involving sub-SELECTs.

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We'll now use "exists" for EXISTS(SELECT ...), "array" for ARRAY(SELECT
...), or the sub-select's own result column name for a simple expression
sub-select.  Previously, you usually got "?column?" in such cases.

Marti Raudsepp, reviewed by Kyotaro Horiugchi
This commit is contained in:
Tom Lane
2011-10-01 14:01:46 -04:00
parent 878b74e094
commit 5ec6b7f1b8
6 changed files with 59 additions and 16 deletions
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42
src/backend/parser/parse_target.c
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@ -1610,6 +1610,48 @@ FigureColnameInternal(Node *node, char **name)
break;
case T_CollateClause:
return FigureColnameInternal(((CollateClause *) node)->arg, name);
case T_SubLink:
switch (((SubLink *) node)->subLinkType)
{
case EXISTS_SUBLINK:
*name = "exists";
return 2;
case ARRAY_SUBLINK:
*name = "array";
return 2;
case EXPR_SUBLINK:
{
/* Get column name of the subquery's single target */
SubLink *sublink = (SubLink *) node;
Query *query = (Query *) sublink->subselect;
/*
* The subquery has probably already been transformed,
* but let's be careful and check that. (The reason
* we can see a transformed subquery here is that
* transformSubLink is lazy and modifies the SubLink
* node in-place.)
*/
if (IsA(query, Query))
{
TargetEntry *te = (TargetEntry *) linitial(query->targetList);
if (te->resname)
{
*name = te->resname;
return 2;
}
}
}
break;
/* As with other operator-like nodes, these have no names */
case ALL_SUBLINK:
case ANY_SUBLINK:
case ROWCOMPARE_SUBLINK:
case CTE_SUBLINK:
break;
}
break;
case T_CaseExpr:
strength = FigureColnameInternal((Node *) ((CaseExpr *) node)->defresult,
name);