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

1 files changed, 27 insertions, 15 deletions

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 $
  *
  *-------------------------------------------------------------------------
  */
@@ -102,6 +102,7 @@ parseCheckAggregates(ParseState *pstate, Query *qry)
 	bool		have_non_var_grouping;
 	ListCell   *l;
 	bool		hasJoinRTEs;
+	bool		hasSelfRefRTEs;
 	PlannerInfo *root;
 	Node	   *clause;
 
@@ -109,6 +110,21 @@ parseCheckAggregates(ParseState *pstate, Query *qry)
 	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.
 	 *
 	 * (Note this check should appear first to deliver an appropriate error
@@ -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))));
 }