From 44d5be0e5308e951c0c5dc522b4bcacf2bcbc476 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sat, 4 Oct 2008 21:56:55 +0000
Subject: Implement SQL-standard WITH clauses, including WITH RECURSIVE.

There are some unimplemented aspects: recursive queries must use UNION ALL
(should allow UNION too), and we don't have SEARCH or CYCLE clauses.
These might or might not get done for 8.4, but even without them it's a
pretty useful feature.

There are also a couple of small loose ends and definitional quibbles,
which I'll send a memo about to pgsql-hackers shortly.  But let's land
the patch now so we can get on with other development.

Yoshiyuki Asaba, with lots of help from Tatsuo Ishii and Tom Lane
---
 src/backend/parser/parse_agg.c | 42 +++++++++++++++++++++++++++---------------
 1 file changed, 27 insertions(+), 15 deletions(-)

(limited to 'src/backend/parser/parse_agg.c')

diff --git a/src/backend/parser/parse_agg.c b/src/backend/parser/parse_agg.c
index d85f64c7abc..e2645462d57 100644
--- a/src/backend/parser/parse_agg.c
+++ b/src/backend/parser/parse_agg.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/parser/parse_agg.c,v 1.83 2008/09/01 20:42:44 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/parser/parse_agg.c,v 1.84 2008/10/04 21:56:54 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -102,12 +102,28 @@ parseCheckAggregates(ParseState *pstate, Query *qry)
 	bool		have_non_var_grouping;
 	ListCell   *l;
 	bool		hasJoinRTEs;
+	bool		hasSelfRefRTEs;
 	PlannerInfo *root;
 	Node	   *clause;
 
 	/* This should only be called if we found aggregates or grouping */
 	Assert(pstate->p_hasAggs || qry->groupClause || qry->havingQual);
 
+	/*
+	 * Scan the range table to see if there are JOIN or self-reference CTE
+	 * entries.  We'll need this info below.
+	 */
+	hasJoinRTEs = hasSelfRefRTEs = false;
+	foreach(l, pstate->p_rtable)
+	{
+		RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
+
+		if (rte->rtekind == RTE_JOIN)
+			hasJoinRTEs = true;
+		else if (rte->rtekind == RTE_CTE && rte->self_reference)
+			hasSelfRefRTEs = true;
+	}
+
 	/*
 	 * Aggregates must never appear in WHERE or JOIN/ON clauses.
 	 *
@@ -157,20 +173,6 @@ parseCheckAggregates(ParseState *pstate, Query *qry)
 	 * underlying vars, so that aliased and unaliased vars will be correctly
 	 * taken as equal.	We can skip the expense of doing this if no rangetable
 	 * entries are RTE_JOIN kind.
-	 */
-	hasJoinRTEs = false;
-	foreach(l, pstate->p_rtable)
-	{
-		RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
-
-		if (rte->rtekind == RTE_JOIN)
-		{
-			hasJoinRTEs = true;
-			break;
-		}
-	}
-
-	/*
 	 * We use the planner's flatten_join_alias_vars routine to do the
 	 * flattening; it wants a PlannerInfo root node, which fortunately can be
 	 * mostly dummy.
@@ -217,6 +219,16 @@ parseCheckAggregates(ParseState *pstate, Query *qry)
 		clause = flatten_join_alias_vars(root, clause);
 	check_ungrouped_columns(clause, pstate,
 							groupClauses, have_non_var_grouping);
+
+	/*
+	 * Per spec, aggregates can't appear in a recursive term.
+	 */
+	if (pstate->p_hasAggs && hasSelfRefRTEs)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_RECURSION),
+				 errmsg("aggregates not allowed in a recursive query's recursive term"),
+				 parser_errposition(pstate,
+									locate_agg_of_level((Node *) qry, 0))));
 }
 
 
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