Horton

Re: [HACKERS] AdvanceXLInsertBuffer vs. WAL segment compressibility

Chapman Flack <chap@anastigmatix.net>

View thread View on postgr.es
From: Chapman Flack <chap@anastigmatix.net>
To: Michael Paquier <michael@paquier.xyz>, Stephen Frost <sfrost@snowman.net>
Cc: Daniel Gustafsson <daniel@yesql.se>, Tom Lane <tgl@sss.pgh.pa.us>, Michael Paquier <michael.paquier@gmail.com>, Heikki Linnakangas <hlinnaka@iki.fi>, Robert Haas <robertmhaas@gmail.com>, Bruce Momjian <bruce@momjian.us>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2018-03-27T22:32:08Z
Lists: pgsql-hackers 
On 03/26/18 01:43, Michael Paquier wrote:

> Have a look at BKP_REMOVABLE then.  This was moved to page headers in
> 2dd9322, still it seems to me that the small benefits outlined on this
> thread don't justify breaking tools relying on this flag set, especially
> if there is no replacement for it.

Is 2dd9322 a commit? I'm having difficulty finding it:

https://git.postgresql.org/gitweb/?p=postgresql.git&a=search&h=HEAD&st=commit&s=2dd9322

Am I searching wrong?

I probably won't have more time to look at this tonight, but could
I ask in advance for examples of tools that would need this bit when
encountering unwritten pages at the end of a segment?

I don't mean that as snark; it's just nonobvious to me and I might need
a little nudge where to look.

-Chap

Commits

  1. Ensure that WAL pages skipped by a forced WAL switch are zero-filled.

  2. Improve scalability of WAL insertions.

  3. Move BKP_REMOVABLE bit from individual WAL records to WAL page headers.