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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: Stephen Frost <sfrost@snowman.net>
Cc: David Steele <david@pgmasters.net>, Beena Emerson <memissemerson@gmail.com>, tushar <tushar.ahuja@enterprisedb.com>, Prabhat Sahu <prabhat.sahu@enterprisedb.com>, Ashutosh Sharma <ashu.coek88@gmail.com>, Jim Nasby <Jim.Nasby@bluetreble.com>, Kuntal Ghosh <kuntalghosh.2007@gmail.com>, Andres Freund <andres@anarazel.de>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2017-03-21T19:22:57Z
Lists: pgsql-hackers 
On Tue, Mar 21, 2017 at 9:04 AM, Stephen Frost <sfrost@snowman.net> wrote:
> In short, I'm also concerned about this change to make WAL file names no
> longer match up with LSNs and also about the odd stepping that you get
> as a result of this change when it comes to WAL file names.

OK, that's a bit surprising to me, but what do you want to do about
it?  If you take the approach that Beena did, then you lose the
correspondence with LSNs, which is admittedly not great but there are
already helper functions available to deal with LSN -> filename
mappings and I assume those will continue to work. If you take the
opposite approach, then WAL filenames stop being consecutive, which
seems to me to be far worse in terms of user and tool confusion.  Also
note that, both currently and with the patch, you can also reduce the
WAL segment size.  David's proposed naming scheme doesn't handle that
case, I think, and I think it would be all kinds of a bad idea to use
one file-naming approach for segments < 16MB and a separate approach
for segments > 16MB.  That's not making anything easier for users or
tool authors.

-- 
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.