From 889592344c48d3965567f331b4ea89dfe6447bce Mon Sep 17 00:00:00 2001
From: Tom Lane
Date: Wed, 2 Jun 2021 14:38:14 -0400
Subject: Fix planner's row-mark code for inheritance from a foreign table.

Commit 428b260f8 broke planning of cases where row marks are needed
(SELECT FOR UPDATE, etc) and one of the query's tables is a foreign
table that has regular table(s) as inheritance children.  We got the
reverse case right, but apparently were thinking that foreign tables
couldn't be inheritance parents.  Not so; so we need to be able to
add a CTID junk column while adding a new child, not only a wholerow
junk column.

Back-patch to v12 where the faulty code came in.

Amit Langote

Discussion: https://postgr.es/m/CA+HiwqEmo3FV1LAQ4TVyS2h1WM=kMkZUmbNuZSCnfHvMcUcPeA@mail.gmail.com
---
 src/backend/optimizer/util/inherit.c | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

(limited to 'src')

diff --git a/src/backend/optimizer/util/inherit.c b/src/backend/optimizer/util/inherit.c
index 13f67ab7449..992ef87b9da 100644
--- a/src/backend/optimizer/util/inherit.c
+++ b/src/backend/optimizer/util/inherit.c
@@ -232,8 +232,25 @@ expand_inherited_rtentry(PlannerInfo *root, RelOptInfo *rel,
 		char		resname[32];
 		List	   *newvars = NIL;
 
-		/* The old PlanRowMark should already have necessitated adding TID */
-		Assert(old_allMarkTypes & ~(1 << ROW_MARK_COPY));
+		/* Add TID junk Var if needed, unless we had it already */
+		if (new_allMarkTypes & ~(1 << ROW_MARK_COPY) &&
+			!(old_allMarkTypes & ~(1 << ROW_MARK_COPY)))
+		{
+			/* Need to fetch TID */
+			var = makeVar(oldrc->rti,
+						  SelfItemPointerAttributeNumber,
+						  TIDOID,
+						  -1,
+						  InvalidOid,
+						  0);
+			snprintf(resname, sizeof(resname), "ctid%u", oldrc->rowmarkId);
+			tle = makeTargetEntry((Expr *) var,
+								  list_length(root->processed_tlist) + 1,
+								  pstrdup(resname),
+								  true);
+			root->processed_tlist = lappend(root->processed_tlist, tle);
+			newvars = lappend(newvars, var);
+		}
 
 		/* Add whole-row junk Var if needed, unless we had it already */
 		if ((new_allMarkTypes & (1 << ROW_MARK_COPY)) &&
-- 
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