Horton

bug: ALTER TABLE ADD VIRTUAL GENERATED COLUMN with table rewrite

jian he <jian.universality@gmail.com>

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From: jian he <jian.universality@gmail.com>
To: PostgreSQL-development <pgsql-hackers@postgresql.org>
Cc: Peter <peter@eisentraut.org>
Date: 2025-02-27T15:00:51Z
Lists: pgsql-hackers

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hi.


bug demo:
CREATE TABLE gtest20a (a int PRIMARY KEY, b int GENERATED ALWAYS AS (a
* 2) VIRTUAL);
ALTER TABLE gtest20a ADD COLUMN c float8 DEFAULT RANDOM() CHECK (b < 60);
ERROR:  no generation expression found for column number 2 of table
"pg_temp_17306"

issue is that
in ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap)
we need use existing (tab->relid) relation get the generated
expression, not use OIDNewHeap,
since we don't populate OIDNewHeap related generated expressions.

The attached patch fixes this issue.

Commits

  1. Fix ALTER TABLE ADD VIRTUAL GENERATED COLUMN when table rewrite