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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: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
Cc: Robert Haas <robertmhaas@gmail.com>, Andres Freund <andres@anarazel.de>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2016-12-19T09:44:50Z
Lists: pgsql-hackers

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Hello all,

Please find attached a patch to make wal segment size initdb configurable.

The attached patch removes --with-wal-segsize configure option and adds a
new initdb option --wal-segsize. The module initdb passes the wal-segsize
value into an environment variable which is used to overwrite the guc value
wal_ segment_size and set the internal variables : XLogSegSize and
XLOG_SEG_SIZE (xlog_internal.h). The default wal_segment_size is not
changed but I have increased the maximum size to 1GB.

Since  XLOG_SEG_SIZE is now variable, it could not be used directly in
src/bin modules and few macros and few changes had to be made:
  -  in guc.c , remove GUC_UNIT_XSEGS which used XLOG_SEG_SIZE and
introduce show functions for the guc which used the unit (min_wal_size and
max_wal_size).
  -  For pg_basebackup, add new replication command SHOW_WAL_SEGSZ to fetch
the wal_segment_size in bytes.
  - pg_controldata, pg_resetxlog, pg_rewind, fetch the xlog_seg_size from
the ControlFile.
  - Since pg_xlogdump reads the wal files, it uses the file size to
determine the xlog_seg_size.
  - In pg_test_fsync, a buffer of size XLOG_SEG_SIZE was created, filled
with random data and written to a temporary file to check for any
write/fsync error before performing the tests. Since it does not affect the
actual performance results, the XLOG_SEG_SIZE in the module is replaced
with the default value (16MB).

Please note that the documents are not updated in this patch.

Feedback and suggestions are welcome.
--

Beena Emerson

Have a Great Day!

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.