BUG #18852: Unexpected expression in subquery output

The following bug has been logged on the website:

Bug reference: 18852
Logged by: Robins Tharakan
Email address: tharakan(at)gmail(dot)com
PostgreSQL version: Unsupported/Unknown
Operating system: Ubuntu
Description:

Hi,

The following SQL returns this error:

$ psql -f repro.sql >/dev/null
psql:repro.sql:11: ERROR: unexpected expression in subquery output

$ cat repro.sql
CREATE SCHEMA a;
CREATE SCHEMA b;
CREATE EXTENSION postgres_fdw ;
CREATE SERVER d FOREIGN DATA WRAPPER postgres_fdw;
CREATE FOREIGN TABLE a.e () SERVER d;
CREATE FOREIGN TABLE a.f (g text) SERVER d;
CREATE FOREIGN TABLE b.h () SERVER d;
SELECT FROM a.f RIGHT JOIN b.h ON EXISTS (SELECT FROM a.e WHERE (SELECT
NULL) > g) LIMIT 9;

- The issue surfaced after commit 824dbea3e41efa3b35094163c834988dea7eb139
[1]
Testing for start crashing
Checking (682c5be25c2~0) - 682c5be25c - fail
Checking (682c5be25c2~10) - 2b73a8cd33 - fail
Checking (682c5be25c2~30) - 3691edfab9 - fail
.
.
Checking (682c5be25c2~3470) - 278eb13c48 - pass
Checking (682c5be25c2~3450) - 7db01fbcef - fail
Checking (682c5be25c2~3460) - 719b342d36 - fail
Checking (682c5be25c2~3465) - c2a465b2c9 - fail
Checking (682c5be25c2~3467) - 7636725b92 - fail
Checking (682c5be25c2~3468) - bfc677c3bc - fail
Checking (682c5be25c2~3469) - 824dbea3e4 - fail
Surfacing Commit is 824dbea3e41efa3b35094163c834988dea7eb139

-
robins

Reference:
1.
https://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=824dbea3e41efa3b35094163c834988dea7eb139