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: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Dilip Kumar <dilipbalaut@gmail.com>, Justin Pryzby <pryzby@telsasoft.com>, Robert Haas <robertmhaas@gmail.com>, Ashutosh Sharma <ashu.coek88@gmail.com>, Maciek Sakrejda <m.sakrejda@gmail.com>, Bruce Momjian <bruce@momjian.us>, Alvaro Herrera <alvherre@alvh.no-ip.org>, Andrew Dunstan <andrew@dunslane.net>, Heikki Linnakangas <hlinnaka@iki.fi>, pgsql-hackers@lists.postgresql.org
Date: 2022-08-04T22:51:47Z
Lists: pgsql-hackers 
Hi,

On 2022-08-04 18:05:25 -0400, Tom Lane wrote:
> Andres Freund <andres@anarazel.de> writes:
> > Yea. I think at the very least we need to start holding interrupts before the
> > DropDatabaseBuffers() and do so until commit. That's probably best done by
> > doing the transaction commit inside dropdb.
> 
> We've talked before about ignoring interrupts across commit, but
> I find the idea a bit scary.

I'm not actually suggesting to do so across commit, just until the
commit. Maintaining that seems easiest if dropdb() does the commit internally.


> In any case, DROP DATABASE is far from the only place with a problem.

What other place has a database corrupting potential of this magnitude just
because interrupts are accepted?  We throw valid s_b contents away and then
accept interrupts before committing - with predictable results. We also accept
interrupts as part of deleting the db data dir (due to catalog access).

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.