Horton

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

Andrew Dunstan <andrew@dunslane.net>

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From: Andrew Dunstan <andrew@dunslane.net>
To: Heikki Linnakangas <hlinnaka@iki.fi>, Dilip Kumar <dilipbalaut@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2021-06-15T13:31:22Z
Lists: pgsql-hackers 
On 6/15/21 8:04 AM, Heikki Linnakangas wrote:
>
> Yeah, WAL-logging the contents of the source database would certainly
> be less weird than the current system. As Julien also pointed out, the
> question is, are there people using on "CREATE DATABASE foo TEMPLATE
> bar" to copy a large source database, on the premise that it's fast
> because it skips WAL-logging?


I'm 100% certain there are. It's not even a niche case.


>
> In principle, we could have both mechanisms, and use the new
> WAL-logged system if the database is small, and the old system with
> checkpoints if it's large. But I don't like idea of having to maintain
> both.
>
>

Rather than use size, I'd be inclined to say use this if the source
database is marked as a template, and use the copydir approach for
anything that isn't.


cheers


andrew


--
Andrew Dunstan
EDB: https://www.enterprisedb.com

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.