Horton

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

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Dilip Kumar <dilipbalaut@gmail.com>
Cc: 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>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2022-03-23T12:24:02Z
Lists: pgsql-hackers 
On Wed, Mar 23, 2022 at 4:42 AM Dilip Kumar <dilipbalaut@gmail.com> wrote:
> Okay this is an interesting point.  So one option is that in case of
> failure while using the wal log strategy we do not remove the database
> directory, because an abort transaction will take care of removing the
> relation file.  But then in failure case we will leave the orphaned
> database directory with version file and the relmap file.  Another
> option is to do the redundant cleanup as we are doing now.  Any other
> options?

I think our overriding goal should be to get everything using one
mechanism. It doesn't look straightforward to get everything to go
through the PendingRelDelete mechanism, because as you say, it can't
handle non-relation files or directories. However, what if we opt out
of that mechanism? We could do that either by not using
RelationCreateStorage() in the first place and directly calling
smgrcreate(), or by using RelationPreserveStorage() afterwards to yank
the file back out of the list.

-- 
Robert Haas
EDB: http://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.