Horton

BUG #19435: Error: "No relation entry for relid 2" Triggered by Complex Join with Self-Referencing Tables

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From: PG Bug reporting form <noreply@postgresql.org>
To: pgsql-bugs@lists.postgresql.org
Cc: ammmkilo@163.com
Date: 2026-03-16T15:51:30Z
Lists: pgsql-bugs 
The following bug has been logged on the website:

Bug reference:      19435
Logged by:          Hang ammmkilo
Email address:      ammmkilo@163.com
PostgreSQL version: 18.3
Operating system:   Ubuntu 22.04
Description:        

A user encountered an error when attempting to execute a query involving
multiple RIGHT JOIN operations and a NATURAL JOIN on the same table
(pg_table_a). The error message returned was:
[XX000]ERROR: no relation entry for relid 2
This error seems to be an internal one and should not be triggered by users.
It might be a bug.
```sql
DROP TABLE IF EXISTS pg_table_a;

CREATE TABLE pg_table_a (
    id INTEGER PRIMARY KEY,
    col_bool BOOLEAN
);

INSERT INTO pg_table_a (id, col_bool)
VALUES (5, TRUE);

SELECT  1 AS c1
FROM (
    pg_table_a AS tom0
    RIGHT JOIN (
        (pg_table_a AS tom1 NATURAL JOIN pg_table_a AS tom2)
        RIGHT JOIN pg_table_a AS tom3
        ON tom1.col_bool IS NOT NULL
    )
    ON tom1.col_bool
);
```

Commits

  1. Further improve commentary about ChangeVarNodesWalkExpression()

  2. Improve commentary about ChangeVarNodesWalkExpression().

  3. Fix self-join removal to update bare Var references in join clauses

  4. Implement Self-Join Elimination