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Re: increasing the default WAL segment size

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Bruce Momjian <bruce@momjian.us>
Cc: Andres Freund <andres@anarazel.de>, Tom Lane <tgl@sss.pgh.pa.us>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2016-08-25T15:01:40Z
Lists: pgsql-hackers 
On Thu, Aug 25, 2016 at 10:39 AM, Bruce Momjian <bruce@momjian.us> wrote:
> Another issue is that many users are coming from database products that
> have significant performance hits in switching WAL files so they might
> be tempted to set very high segment sizes in inappropriate cases.

Well, we have some hit there, too.  It may be smaller, but it's
certainly not zero.

I'm generally in favor of preventing people from setting ridiculous
values for settings; we shouldn't let somebody set the WAL segment
size to 8kB or something silly like that.  But it's more important to
enable legitimate uses than it is to prohibit inappropriate uses.  If
a particular value of a particular setting may be legitimately useful
to some users, we should allow it, even if some other user might
choose that value under false assumptions.

In short, let's eschew nannyism.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Make WAL segment size configurable at initdb time.

  2. Perform only one ReadControlFile() during startup.

  3. Introduce BYTES unit for GUCs.

  4. Remove useless duplicate inclusions of system header files.

  5. Refactor other replication commands to use DestRemoteSimple.

  6. Add a SHOW command to the replication command language.

  7. Add a new DestReceiver for printing tuples without catalog access.

  8. Support fls().

  9. Extend yesterday's patch making BLCKSZ and RELSEG_SIZE configurable to also

  10. Commit the reasonably uncontroversial parts of J.R. Nield's PITR patch, to

  11. XLOG (also known as WAL -:)) Bootstrap/Startup/Shutdown.

  12. Transaction log manager core code.