Bug reference: 19046 Logged by: Runyuan He Email address: runyuan@berkeley.edu PostgreSQL version: 18rc1 Operating system: Linux (x86) Description:
Bug Description: When using json_array() function with a column reference from table t inside a subquery, and then performing a RIGHT JOIN with condition FALSE, the result incorrectly returns [3, 2] instead of the expected NULL value.
Reproducible Example: CREATE TABLE t(c INT); INSERT INTO t VALUES (1);
SELECT sub.c FROM (SELECT json_array(3, 2, t.c) AS c FROM t) AS sub RIGHT JOIN t ON FALSE; -- PostgreSQL 16.x: Returns NULL (CORRECT) -- PostgreSQL 17.6, 17.rc1: Returns [3, 2] (INCORRECT) -- PostgreSQL 18rc1: Returns [3, 2] (INCORRECT)
SELECT sub.c FROM (SELECT json_array(3, 2, t.c) AS c FROM t) AS sub; -- Returns [3, 2, 1] (CORRECT)
SELECT sub.c FROM (SELECT json_array(3, 2, 1) AS c FROM t) AS sub RIGHT JOIN t ON FALSE; -- Returns Null (CORRECT)
I can reproduce this on HEAD. The following commit introduced this incorrect result:
commit cb8e50a4a09fe541e32cd54ea90a97f2924121a1 Author: Tom Lane <tgl@sss.pgh.pa.us> Date: Fri Aug 30 12:42:12 2024 -0400
Avoid inserting PlaceHolderVars in cases where pre-v16 PG did not.
