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" In ATRewriteTable, the variable OIDNewHeap (if valid) corresponding pg_attrdef default expression entry was not populated. So OIDNewHeap cannot be used to call expand_generated_columns_in_expr or build_generation_expression. Therefore in ATRewriteTable, we can only use the existing relation to expand the generated expression. Author: jian he <jian.universality@gmail.com> Reviewed-by: Srinath Reddy <srinath2133@gmail.com> Discussion: https://www.postgresql.org/message-id/flat/CACJufxEJ%3DFoajabWXjszo_yrQeKSxdZ87KJqBW373rSbajKGAA%40mail.gmail.com
PostgreSQL Database Management System
This directory contains the source code distribution of the PostgreSQL database management system.
PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings.
Copyright and license information can be found in the file COPYRIGHT.
General documentation about this version of PostgreSQL can be found at https://www.postgresql.org/docs/devel/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/devel/installation.html.
The latest version of this software, and related software, may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.