Feedback-ID: ia2694551:Fastmail
Date: Thu, 11 Jul 2024 15:05:09 +0200
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Ron Johnson <ronljohnsonjr@gmail.com>
Cc: pgsql-general <pgsql-general@lists.postgresql.org>
Subject: Re: Dropping column from big table
Message-ID: <202407111305.swxs3no6pmhy@alvherre.pgsql>
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On 2024-Jul-11, Ron Johnson wrote:

> Anyway, DROP is the easy part; it's ADD COLUMN that can take a lot of time
> (depending on whether or not you populate the column with a default value).

Actually, ADD COLUMN with a default does not rewrite the entire table
either, starting from pg11.

"Major enhancements in PostgreSQL 11 include:
[...]
* Many other useful performance improvements, including the ability to
  avoid a table rewrite for ALTER TABLE ... ADD COLUMN with a non-null
  column default."

https://www.postgresql.org/docs/11/release-11.html

-- 
Álvaro Herrera               48°01'N 7°57'E  —  https://www.EnterpriseDB.com/