From 4bea91f21f61d01bd40a4191a4a8c82d0959fffe Mon Sep 17 00:00:00 2001
From: Masahiko Sawada
Date: Mon, 20 Oct 2025 10:38:52 -0700
Subject: Support COPY TO for partitioned tables.

Previously, COPY TO command didn't support directly specifying
partitioned tables so users had to use COPY (SELECT ...) TO variant.

This commit adds direct COPY TO support for partitioned
tables, improving both usability and performance. Performance tests
show it's faster than the COPY (SELECT ...) TO variant as it avoids
the overheads of query processing and sending results to the COPY TO
command.

When used with partitioned tables, COPY TO copies the same rows as
SELECT * FROM table. Row-level security policies of the partitioned
table are applied in the same way as when executing COPY TO on a plain
table.

Author: jian he <jian.universality@gmail.com>
Reviewed-by: vignesh C <vignesh21@gmail.com>
Reviewed-by: David Rowley <dgrowleyml@gmail.com>
Reviewed-by: Melih Mutlu <m.melihmutlu@gmail.com>
Reviewed-by: Kirill Reshke <reshkekirill@gmail.com>
Reviewed-by: Atsushi Torikoshi <torikoshia@oss.nttdata.com>
Reviewed-by: Álvaro Herrera <alvherre@kurilemu.de>
Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Discussion: https://postgr.es/m/CACJufxEZt%2BG19Ors3bQUq-42-61__C%3Dy5k2wk%3DsHEFRusu7%3DiQ%40mail.gmail.com
---
 contrib/postgres_fdw/sql/postgres_fdw.sql | 3 +++
 1 file changed, 3 insertions(+)

(limited to 'contrib/postgres_fdw/sql/postgres_fdw.sql')

diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index 3b7da128519..9a8f9e28135 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -3941,6 +3941,9 @@ INSERT INTO result_tbl SELECT * FROM async_pt WHERE b === 505;
 SELECT * FROM result_tbl ORDER BY a;
 DELETE FROM result_tbl;
 
+-- Test COPY TO when foreign table is partition
+COPY async_pt TO stdout; --error
+
 DROP FOREIGN TABLE async_p3;
 DROP TABLE base_tbl3;
 
-- 
cgit v1.2.3

