Horton

Re: [Proposal] Fully WAL logged CREATE DATABASE - No Checkpoints

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Julien Rouhaud <rjuju123@gmail.com>, Bruce Momjian <bruce@momjian.us>, Ashutosh Sharma <ashu.coek88@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>, Greg Nancarrow <gregn4422@gmail.com>, Heikki Linnakangas <hlinnaka@iki.fi>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2022-02-10T23:10:48Z
Lists: pgsql-hackers 
Hi,

On 2022-02-10 10:32:42 -0500, Robert Haas wrote:
> I won't really be surprised if we hear that someone has a 10GB
> template database and likes to make a ton of copies and only change
> 500 rows in each one while replicating the whole thing over a slow
> WAN. That can definitely happen, and I'm sure whoever is doing that
> has reasons for it which they consider good and sufficient. However, I
> don't think there are likely to be a ton of people doing stuff like
> that - just a few.

Yea. I would be a bit more concerned if we made creating template databases
very cheap, e.g. by using file copy-on-write functionality like we have for
pg_upgrade.  But right now it's a fairly hefty operation anyway.

Greetings,

Andres Freund

Commits

  1. When using the WAL-logged CREATE DATABASE strategy, bulk extend.

  2. Avoid using a fake relcache entry to own an SmgrRelation.

  3. Fix data-corruption hazard in WAL-logged CREATE DATABASE.

  4. initdb: When running CREATE DATABASE, use STRATEGY = WAL_COPY.

  5. Simplify a needlessly-complicated regular expression.

  6. In 020_createdb.pl, change order of command-line arguments.

  7. Add new block-by-block strategy for CREATE DATABASE.

  8. Fix replay of create database records on standby

  9. Refactor code for reading and writing relation map files.

  10. Replace RelationOpenSmgr() with RelationGetSmgr().

  11. Refactor the fsync queue for wider use.