Horton

Re: Move pg_attribute.attcompression to earlier in struct for reduced size?

Michael Paquier <michael@paquier.xyz>

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From: Michael Paquier <michael@paquier.xyz>
To: Andres Freund <andres@anarazel.de>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, pgsql-hackers@postgresql.org, Dilip Kumar <dilipbalaut@gmail.com>, Robert Haas <robertmhaas@gmail.com>
Date: 2021-05-24T04:09:18Z
Lists: pgsql-hackers

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On Fri, May 21, 2021 at 02:19:29PM -0700, Andres Freund wrote:
> During VACUUM FULL reform_and_rewrite_tuple() detoasts the old value if
> it was compressed with a different method, while in
> TopTransactionContext. There's nothing freeing that until
> TopTransactionContext ends - obviously not great for a large relation
> being VACUUM FULLed.

Yeah, that's not good.  The confusion comes from the fact that we'd
just overwrite the values without freeing them out if recompressed, so
something like the attached would be fine?
--
Michael

Commits

  1. Remove forced toast recompression in VACUUM FULL/CLUSTER

  2. Rethink definition of pg_attribute.attcompression.

  3. Fix memory leak when de-toasting compressed values in VACUUM FULL/CLUSTER

  4. Re-order pg_attribute columns to eliminate some padding space.

  5. Add more TAP tests for pg_dump with attribute compression