Support data-modifying commands (INSERT/UPDATE/DELETE) in WITH.

This patch implements data-modifying WITH queries according to the
semantics that the updates all happen with the same command counter value,
and in an unspecified order.  Therefore one WITH clause can't see the
effects of another, nor can the outer query see the effects other than
through the RETURNING values.  And attempts to do conflicting updates will
have unpredictable results.  We'll need to document all that.

This commit just fixes the code; documentation updates are waiting on
author.

Marko Tiikkaja and Hitoshi Harada

1 files changed, 20 insertions, 1 deletions

diff --git a/src/backend/parser/parse_relation.c b/src/backend/parser/parse_relation.c
index 033ed411fde..c7000b99153 100644
--- a/src/backend/parser/parse_relation.c
+++ b/src/backend/parser/parse_relation.c
@@ -1363,10 +1363,11 @@ RangeTblEntry *
 addRangeTableEntryForCTE(ParseState *pstate,
 						 CommonTableExpr *cte,
 						 Index levelsup,
-						 Alias *alias,
+						 RangeVar *rv,
 						 bool inFromCl)
 {
 	RangeTblEntry *rte = makeNode(RangeTblEntry);
+	Alias	   *alias = rv->alias;
 	char	   *refname = alias ? alias->aliasname : cte->ctename;
 	Alias	   *eref;
 	int			numaliases;
@@ -1384,6 +1385,24 @@ addRangeTableEntryForCTE(ParseState *pstate,
 	if (!rte->self_reference)
 		cte->cterefcount++;
 
+	/*
+	 * We throw error if the CTE is INSERT/UPDATE/DELETE without RETURNING.
+	 * This won't get checked in case of a self-reference, but that's OK
+	 * because data-modifying CTEs aren't allowed to be recursive anyhow.
+	 */
+	if (IsA(cte->ctequery, Query))
+	{
+		Query  *ctequery = (Query *) cte->ctequery;
+
+		if (ctequery->commandType != CMD_SELECT &&
+			ctequery->returningList == NIL)
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("WITH query \"%s\" does not have a RETURNING clause",
+							cte->ctename),
+					 parser_errposition(pstate, rv->location)));
+	}
+
 	rte->ctecoltypes = cte->ctecoltypes;
 	rte->ctecoltypmods = cte->ctecoltypmods;
 	rte->ctecolcollations = cte->ctecolcollations;