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Re: increasing the default WAL segment size

Beena Emerson <memissemerson@gmail.com>

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From: Beena Emerson <memissemerson@gmail.com>
To: Ashutosh Sharma <ashu.coek88@gmail.com>
Cc: 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: 2017-03-10T05:53:57Z
Lists: pgsql-hackers

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Hello,

On Tue, Mar 7, 2017 at 10:46 AM, Ashutosh Sharma <ashu.coek88@gmail.com>
wrote:

> Hi,
>
> I took a look at this patch. Overall, the patch looks good to me.
> However, there are some review comments that I would like to share,
>
> 1. I think the macro 'PATH_MAX' used in pg_waldump.c file is specific
> to Linux. It needs to be changed to some constant value or may be
> MAXPGPATH inorder to make it platform independent.
>
> 2. As already mentioned by Jim and Kuntal upthread, you are trying to
> detect the configured WAL segment size in pg_waldump.c and
> pg_standby.c files based on the size of the random WAL file which
> doesn't look like a good idea. But, then I think the only option we
> have is to pass the location of pg_control file to pg_waldump module
> along with the start and end wal segments.
>
> 3. When trying to compile '02-initdb-walsegsize-v2.patch' on Windows,
> I got this warning message,
>
> Warning    1    warning C4005: 'DEFAULT_XLOG_SEG_SIZE' : macro
> redefinition
> c:\users\ashu\postgresql\src\include\pg_config_manual.h    20
>
> Apart from these, I am not having any comments as of now. I am still
> validating the patch on Windows. If I find any issues i will update
> it.
>
> Thank you for your reviews Kuntal, Jim, Ashutosh

Attached in an updated 02 patch which:

   1. Call RetrieveXLogSegSize(conn) in pg_receivewal.c
   2. Remove the warning in Windows
   3. Change PATH_MAX in pg_waldump with MAXPGPATH

Regarding the usage of the wal file size as the XLogSegSize, I agree with
what Robert has said. Generally, the wal size will be of the expected
wal_segment_size and to have it any other size, esspecially of a valid
power2 value is extremely rare and I feel it is not a major cause of
concern.

Thank you,

Beena Emerson
EnterpriseDB: http://www.enterprisedb.com

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.