From 0656ed3daa29b00c7c41ad44b407a7165f83d453 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sat, 15 Nov 2008 19:43:47 +0000
Subject: 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.
---
 src/backend/optimizer/prep/prepunion.c | 39 ++++++++++++++++++++++++++++------
 1 file changed, 33 insertions(+), 6 deletions(-)

(limited to 'src/backend/optimizer/prep/prepunion.c')

diff --git a/src/backend/optimizer/prep/prepunion.c b/src/backend/optimizer/prep/prepunion.c
index c2113cb266..bd7c05cc53 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;
@@ -1208,6 +1209,15 @@ expand_inherited_rtentry(PlannerInfo *root, RangeTblEntry *rte, Index rti)
 		return;
 	}
 
+	/*
+	 * 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
@@ -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);
-- 
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