From 481d7d1c01c6335661dd2ccf505298e4b91ee12a Mon Sep 17 00:00:00 2001
From: Heikki Linnakangas <heikki.linnakangas@iki.fi>
Date: Thu, 23 Nov 2023 13:30:13 +0200
Subject: Fix resource leak when a FDW's ForeignAsyncRequest function fails

If an error is thrown after calling CreateWaitEventSet(), the memory
of a WaitEventSet is free'd as it's allocated in the short-lived
memory context, but the file descriptor (on epoll- or kqueue-based
systems) or handles (on Windows) that it contains are leaked.

Use PG_TRY-FINALLY to ensure it gets freed. (On master, I will apply a
better fix, using ResourceOwners to track the WaitEventSet, but that's
not backpatchable.)

The added test doesn't check for leaking resources, so it passed even
before this commit. But at least it covers the code path.

In the passing, fix misleading comment on what the 'nevents' argument
to WaitEventSetWait means.

Report by Alexander Lakhin, analysis and suggestion for the fix by Tom
Lane. Fixes bug #17828. Backpatch to v14 where async execution was
introduced, but master gets a different fix.

Discussion: https://www.postgresql.org/message-id/17828-122da8cba23236be@postgresql.org
Discussion: https://www.postgresql.org/message-id/472235.1678387869@sss.pgh.pa.us
---
 contrib/postgres_fdw/sql/postgres_fdw.sql | 6 ++++++
 1 file changed, 6 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 f40972916a9..80aa7fb56d8 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -3404,6 +3404,12 @@ INSERT INTO result_tbl SELECT a, b, 'AAA' || c FROM async_pt WHERE b === 505;
 SELECT * FROM result_tbl ORDER BY a;
 DELETE FROM result_tbl;
 
+-- Test error handling, if accessing one of the foreign partitions errors out
+CREATE FOREIGN TABLE async_p_broken PARTITION OF async_pt FOR VALUES FROM (10000) TO (10001)
+  SERVER loopback OPTIONS (table_name 'non_existent_table');
+SELECT * FROM async_pt;
+DROP FOREIGN TABLE async_p_broken;
+
 -- Check case where multiple partitions use the same connection
 CREATE TABLE base_tbl3 (a int, b int, c text);
 CREATE FOREIGN TABLE async_p3 PARTITION OF async_pt FOR VALUES FROM (3000) TO (4000)
-- 
cgit v1.2.3

