From: | Andrew Dunstan <andrew(at)dunslane(dot)net> |
---|---|
To: | James Coleman <jtc331(at)gmail(dot)com> |
Cc: | "Bossart, Nathan" <bossartn(at)amazon(dot)com>, "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Document atthasmissing default optimization avoids verification table scan |
Date: | 2022-01-21 21:08:35 |
Message-ID: | c29fe365-4f11-bd0f-083b-8820712927a0@dunslane.net |
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Lists: | pgsql-hackers |
On 1/21/22 13:55, James Coleman wrote:
> On Thu, Jan 20, 2022 at 3:43 PM James Coleman <jtc331(at)gmail(dot)com> wrote:
>> As noted earlier I expect to be posting an updated patch soon.
> Here's the updated series. In 0001 I've moved the documentation tweak
> into the ALTER TABLE notes section. In 0002 I've taken David J's
> suggestion of shortening the "Tip" on the DDL page and mostly using it
> to point people to the Notes section on the ALTER TABLE page.
I don't really like the first part of patch 1, but as it gets removed by
patch 2 we can move past that.
+ Before <productname>PostgreSQL</productname> 11, adding a new
column to a
+ table required rewriting that table, making it a very slow operation.
+ More recent versions can sometimes optimize away this rewrite and
related
+ validation scans. See the notes in <command>ALTER TABLE</command>
for details.
I know what it's replacing refers to release 11, but let's stop doing
that. How about something like this?
Adding a new column can sometimes require rewriting the table,
making it a very slow operation. However in many cases this rewrite
and related verification scans can be optimized away by using an
appropriate default value. See the notes in <command>ALTER
TABLE</command> for details.
cheers
andrew
--
Andrew Dunstan
EDB: https://www.enterprisedb.com
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