From 1a3d9f62c1d158585266200b8bbb2d7d757c4eae Mon Sep 17 00:00:00 2001
From: Etsuro Fujita <efujita@postgresql.org>
Date: Thu, 13 Jun 2019 17:59:17 +0900
Subject: [PATCH] postgres_fdw: Account for triggers in non-direct remote
UPDATE planning.
Previously, in postgresPlanForeignModify, we planned an UPDATE operation
on a foreign table so that we transmit only columns that were explicitly
targets of the UPDATE, so as to avoid unnecessary data transmission, but
if there were BEFORE ROW UPDATE triggers on the foreign table, those
triggers might change values for non-target columns, in which case we
would miss sending changed values for those columns. Prevent optimizing
away transmitting all columns if there are BEFORE ROW UPDATE triggers on
the foreign table.
This is an oversight in commit 7cbe57c34 which added triggers on foreign
tables, so apply the patch all the way back to 9.4 where that came in.
Author: Shohei Mochizuki
Reviewed-by: Amit Langote
Discussion: https://postgr.es/m/201905270152.x4R1q3qi014550@toshiba.co.jp
---
.../postgres_fdw/expected/postgres_fdw.out | 21 ++++++++++++++++++-
contrib/postgres_fdw/postgres_fdw.c | 19 +++++++++++------
contrib/postgres_fdw/sql/postgres_fdw.sql | 5 +++++
3 files changed, 38 insertions(+), 7 deletions(-)
diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 20b627b74ce..c87a33d5da7 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -3063,6 +3063,25 @@ SELECT * from loc1;
2 | skidoo triggered !
(2 rows)
+EXPLAIN (verbose, costs off)
+UPDATE rem1 set f1 = 10; -- all columns should be transmitted
+ QUERY PLAN
+-----------------------------------------------------------------------
+ Update on public.rem1
+ Remote SQL: UPDATE public.loc1 SET f1 = $2, f2 = $3 WHERE ctid = $1
+ -> Foreign Scan on public.rem1
+ Output: 10, f2, ctid, rem1.*
+ Remote SQL: SELECT f1, f2, ctid FROM public.loc1 FOR UPDATE
+(5 rows)
+
+UPDATE rem1 set f1 = 10;
+SELECT * from loc1;
+ f1 | f2
+----+--------------------------------
+ 10 | skidoo triggered ! triggered !
+ 10 | skidoo triggered ! triggered !
+(2 rows)
+
DELETE FROM rem1;
-- Add a second trigger, to check that the changes are propagated correctly
-- from trigger to trigger
@@ -3175,6 +3194,6 @@ NOTICE: trig_row_after(23, skidoo) AFTER ROW INSERT ON rem1
NOTICE: NEW: (13,"test triggered !")
ctid
--------
- (0,27)
+ (0,29)
(1 row)
diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
index c5d9ee43dd9..597b825ac89 100644
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -1176,12 +1176,19 @@ postgresPlanForeignModify(PlannerInfo *root,
/*
* In an INSERT, we transmit all columns that are defined in the foreign
- * table. In an UPDATE, we transmit only columns that were explicitly
- * targets of the UPDATE, so as to avoid unnecessary data transmission.
- * (We can't do that for INSERT since we would miss sending default values
- * for columns not listed in the source statement.)
- */
- if (operation == CMD_INSERT)
+ * table. In an UPDATE, if there are BEFORE ROW UPDATE triggers on the
+ * foreign table, we transmit all columns like INSERT; else we transmit
+ * only columns that were explicitly targets of the UPDATE, so as to avoid
+ * unnecessary data transmission. (We can't do that for INSERT since we
+ * would miss sending default values for columns not listed in the source
+ * statement, and for UPDATE if there are BEFORE ROW UPDATE triggers since
+ * those triggers might change values for non-target columns, in which
+ * case we would miss sending changed values for those columns.)
+ */
+ if (operation == CMD_INSERT ||
+ (operation == CMD_UPDATE &&
+ rel->trigdesc &&
+ rel->trigdesc->trig_update_before_row))
{
TupleDesc tupdesc = RelationGetDescr(rel);
int attnum;
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index 440e69099d7..b93b9d27e40 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -638,6 +638,11 @@ SELECT * from loc1;
UPDATE rem1 set f2 = 'skidoo' RETURNING f2;
SELECT * from loc1;
+EXPLAIN (verbose, costs off)
+UPDATE rem1 set f1 = 10; -- all columns should be transmitted
+UPDATE rem1 set f1 = 10;
+SELECT * from loc1;
+
DELETE FROM rem1;
-- Add a second trigger, to check that the changes are propagated correctly
--
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