Horton

Re: Streaming read-ready sequential scan code

Thomas Munro <thomas.munro@gmail.com>

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From: Thomas Munro <thomas.munro@gmail.com>
To: Melanie Plageman <melanieplageman@gmail.com>
Cc: David Rowley <dgrowleyml@gmail.com>, Heikki Linnakangas <hlinnaka@iki.fi>, Pg Hackers <pgsql-hackers@postgresql.org>, Andres Freund <andres@anarazel.de>
Date: 2024-04-07T01:25:11Z
Lists: pgsql-hackers

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I found a bug in read_stream.c that could be hit with Melanie's
streaming seq scan patch with parallelism enabled and certain buffer
pool conditions.  Short version: there is an edge case where an "if"
needed to be a "while", or we could lose a few blocks.  Here's the fix
for that, longer explanation in commit message.

Commits

  1. Fix unfairness in all-cached parallel seq scan.

  2. Fix if/while thinko in read_stream.c edge case.

  3. Increase default vacuum_buffer_usage_limit to 2MB.

  4. Allow BufferAccessStrategy to limit pin count.

  5. Improve read_stream.c's fast path.

  6. Secondary refactor of heap scanning functions

  7. Preliminary refactor of heap scanning functions

  8. Add VACUUM/ANALYZE BUFFER_USAGE_LIMIT option