Make SELECT FOR UPDATE/SHARE work on inheritance trees, by having the plan

return the tableoid as well as the ctid for any FOR UPDATE targets that
have child tables.  All child tables are listed in the ExecRowMark list,
but the executor just skips the ones that didn't produce the current row.

Curiously, this longstanding restriction doesn't seem to have been documented
anywhere; so no doc changes.

1 files changed, 33 insertions, 6 deletions

diff --git a/src/backend/optimizer/prep/prepunion.c b/src/backend/optimizer/prep/prepunion.c
index c2113cb2669..bd7c05cc53d 100644
--- a/src/backend/optimizer/prep/prepunion.c
+++ b/src/backend/optimizer/prep/prepunion.c
@@ -22,7 +22,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/prepunion.c,v 1.161 2008/11/11 18:13:32 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/prep/prepunion.c,v 1.162 2008/11/15 19:43:46 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1169,6 +1169,7 @@ expand_inherited_rtentry(PlannerInfo *root, RangeTblEntry *rte, Index rti)
 {
 	Query	   *parse = root->parse;
 	Oid			parentOID;
+	RowMarkClause *oldrc;
 	Relation	oldrelation;
 	LOCKMODE	lockmode;
 	List	   *inhOIDs;
@@ -1209,6 +1210,15 @@ expand_inherited_rtentry(PlannerInfo *root, RangeTblEntry *rte, Index rti)
 	}
 
 	/*
+	 * Find out if parent relation is selected FOR UPDATE/SHARE.  If so,
+	 * we need to mark its RowMarkClause as isParent = true, and generate
+	 * a new RowMarkClause for each child.
+	 */
+	oldrc = get_rowmark(parse, rti);
+	if (oldrc)
+		oldrc->isParent = true;
+
+	/*
 	 * Must open the parent relation to examine its tupdesc.  We need not lock
 	 * it since the rewriter already obtained at least AccessShareLock on each
 	 * relation used in the query.
@@ -1221,14 +1231,15 @@ expand_inherited_rtentry(PlannerInfo *root, RangeTblEntry *rte, Index rti)
 	 * in the parse/rewrite/plan pipeline.
 	 *
 	 * If the parent relation is the query's result relation, then we need
-	 * RowExclusiveLock.  Otherwise, check to see if the relation is accessed
-	 * FOR UPDATE/SHARE or not.  We can't just grab AccessShareLock because
-	 * then the executor would be trying to upgrade the lock, leading to
-	 * possible deadlocks.	(This code should match the parser and rewriter.)
+	 * RowExclusiveLock.  Otherwise, if it's accessed FOR UPDATE/SHARE, we
+	 * need RowShareLock; otherwise AccessShareLock.  We can't just grab
+	 * AccessShareLock because then the executor would be trying to upgrade
+	 * the lock, leading to possible deadlocks.  (This code should match the
+	 * parser and rewriter.)
 	 */
 	if (rti == parse->resultRelation)
 		lockmode = RowExclusiveLock;
-	else if (get_rowmark(parse, rti))
+	else if (oldrc)
 		lockmode = RowShareLock;
 	else
 		lockmode = AccessShareLock;
@@ -1283,6 +1294,22 @@ expand_inherited_rtentry(PlannerInfo *root, RangeTblEntry *rte, Index rti)
 		appinfo->parent_reloid = parentOID;
 		appinfos = lappend(appinfos, appinfo);
 
+		/*
+		 * Build a RowMarkClause if parent is marked FOR UPDATE/SHARE.
+		 */
+		if (oldrc)
+		{
+			RowMarkClause *newrc = makeNode(RowMarkClause);
+
+			newrc->rti = childRTindex;
+			newrc->prti = rti;
+			newrc->forUpdate = oldrc->forUpdate;
+			newrc->noWait = oldrc->noWait;
+			newrc->isParent = false;
+
+			parse->rowMarks = lappend(parse->rowMarks, newrc);
+		}
+
 		/* Close child relations, but keep locks */
 		if (childOID != parentOID)
 			heap_close(newrelation, NoLock);