postgres_fdw: Fix crash when estimating joins with functions
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docker run --rm -p 5432:5432 ghcr.io/hackorum-dev/postgres-patch:t253729psql -h localhost -U postgresBuilt from patchset v1 (message #1), September 09, 2026 at 02:16 PM.
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git fetch hackorum t253729_1 && git checkout t253729_1Patchset v1 (message #1) is on t253729_1
Hi,
On master, I found that the following causes a segmentation fault:
CREATE EXTENSION postgres_fdw;
CREATE SERVER loopback FOREIGN DATA WRAPPER postgres_fdw;
CREATE USER MAPPING FOR PUBLIC SERVER loopback;
CREATE TABLE t (i int);
CREATE FOREIGN TABLE ft (i int) SERVER loopback
OPTIONS (table_name 't', use_remote_estimate 'true');
EXPLAIN SELECT * FROM generate_series(1, 3) g JOIN ft ON ft.i = g;
This crash seems to occur because init_func_stub_fpinfo() forgets to copy
the user mapping to the function-side stub, leaving it NULL. The NULL
mapping is then passed to GetConnection() when requesting a remote
estimate, causing the segmentation fault.
This seems to have been introduced by commit 0ee83dd4a99.
The attached patch fixes this by also copying the user mapping from the
foreign side.
Regards,
--
Fujii Masao
Fujii Masao писал(а) 2026-09-09 17:02:
Hi,
On master, I found that the following causes a segmentation fault:
CREATE EXTENSION postgres_fdw;
CREATE SERVER loopback FOREIGN DATA WRAPPER postgres_fdw;
CREATE USER MAPPING FOR PUBLIC SERVER loopback;
CREATE TABLE t (i int);
CREATE FOREIGN TABLE ft (i int) SERVER loopback
OPTIONS (table_name 't', use_remote_estimate 'true');
EXPLAIN SELECT * FROM generate_series(1, 3) g JOIN ft ON ft.i = g;This crash seems to occur because init_func_stub_fpinfo() forgets to
copy
the user mapping to the function-side stub, leaving it NULL. The NULL
mapping is then passed to GetConnection() when requesting a remote
estimate, causing the segmentation fault.This seems to have been introduced by commit 0ee83dd4a99.
The attached patch fixes this by also copying the user mapping from the
foreign side.Regards,
Hi. Thanks. Looks good to me.
--
Best regards,
Alexander Pyhalov,
Postgres Professional