Commitf67b8ae

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Fix crash in assign_collations_walker for EXISTS with empty SELECT list.

We (I think I, actually) forgot about this corner case while codingcollation resolution. Per bug #8648 from Arjen Nienhuis.

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Lines changed: 8 additions & 2 deletions

Original file line number	Diff line number	Diff line change
`@@ -564,16 +564,22 @@ assign_collations_walker(Node node, assign_collations_context context)`
`564`	`564`	`* SubLink. Act as though the Query returns its first output`
`565`	`565`	`* column, which indeed is what it does for EXPR_SUBLINK and`
`566`	`566`	`* ARRAY_SUBLINK cases. In the cases where the SubLink`
`567`		`- * returns boolean, this info will be ignored.`
	`567`	`+ * returns boolean, this info will be ignored.Special case:`
	`568`	`+ * in EXISTS, the Query might return no columns, in which case`
	`569`	`+ * we need do nothing.`
`568`	`570`	`*`
`569`	`571`	`* We needn't recurse, since the Query is already processed.`
`570`	`572`	`*/`
`571`	`573`	`Queryqtree= (Query)node;`
`572`	`574`	`TargetEntry*tent;`
`573`	`575`
	`576`	`+if (qtree->targetList==NIL)`
	`577`	`+return false;`
`574`	`578`	`tent= (TargetEntry*)linitial(qtree->targetList);`
`575`	`579`	`Assert(IsA(tent,TargetEntry));`
`576`		`-Assert(!tent->resjunk);`
	`580`	`+if (tent->resjunk)`
	`581`	`+return false;`
	`582`	`+`
`577`	`583`	`collation=exprCollation((Node*)tent->expr);`
`578`	`584`	`/* collation doesn't change if it's converted to array */`
`579`	`585`	`strength=COLLATE_IMPLICIT;`

Lines changed: 10 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -703,3 +703,13 @@ explain (verbose, costs off)`
`703`	`703`	`One-Time Filter: ("VALUES".column1 = "VALUES".column1)`
`704`	`704`	`(8 rows)`
`705`	`705`
	`706`	`+--`
	`707`	`+-- Check we behave sanely in corner case of empty SELECT list (bug #8648)`
	`708`	`+--`
	`709`	`+create temp table nocolumns();`
	`710`	`+select exists(select * from nocolumns);`
	`711`	`+ ?column?`
	`712`	`+----------`
	`713`	`+ f`
	`714`	`+(1 row)`
	`715`	`+`

Lines changed: 6 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -405,3 +405,9 @@ explain (verbose, costs off)`
`405`	`405`	`explain (verbose, costs off)`
`406`	`406`	`select x, xfrom`
`407`	`407`	`(select (select random()where y=y)as xfrom (values(1),(2)) v(y)) ss;`
	`408`	`+`
	`409`	`+--`
	`410`	`+-- Check we behave sanely in corner case of empty SELECT list (bug #8648)`
	`411`	`+--`
	`412`	`+create temp table nocolumns();`
	`413`	`+select exists(select*from nocolumns);`

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