Horton

Re: refactoring relation extension and BufferAlloc(), faster COPY

David Rowley <dgrowleyml@gmail.com>

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From: David Rowley <dgrowleyml@gmail.com>
To: Andres Freund <andres@anarazel.de>
Cc: vignesh C <vignesh21@gmail.com>, pgsql-hackers@postgresql.org, Thomas Munro <thomas.munro@gmail.com>, Melanie Plageman <melanieplageman@gmail.com>, Yura Sokolov <y.sokolov@postgrespro.ru>, Robert Haas <robertmhaas@gmail.com>
Date: 2023-01-20T00:40:55Z
Lists: pgsql-hackers 
On Tue, 10 Jan 2023 at 15:08, Andres Freund <andres@anarazel.de> wrote:
> Thanks for letting me now. Updated version attached.

I'm not too sure I've qualified for giving a meaningful design review
here, but I have started looking at the patches and so far only made
it as far as 0006.

I noted down the following while reading:

v2-0001:

1. BufferCheckOneLocalPin needs a header comment

v2-0002:

2. The following comment and corresponding code to release the
extension lock has been moved now.

/*
* Release the file-extension lock; it's now OK for someone else to extend
* the relation some more.
*/

I think it's worth detailing out why it's fine to release the
extension lock in the new location. You've added detail to the commit
message but I think you need to do the same in the comments too.

v2-0003

3. FileFallocate() and FileZero() should likely document what they
return, i.e zero on success and non-zero on failure.

4. I'm not quite clear on why you've modified FileGetRawDesc() to call
FileAccess() twice.

v2-0004:

5. Is it worth having two versions of PinLocalBuffer() one to adjust
the usage count and one that does not? Couldn't the version that does
not adjust the count skip doing pg_atomic_read_u32()?

v2-0005
v2-0006

David

Commits

  1. lwlock: Fix quadratic behavior with very long wait lists

  2. Support RBM_ZERO_AND_CLEANUP_LOCK in ExtendBufferedRelTo(), add tests

  3. Use ExtendBufferedRelTo() in XLogReadBufferExtended()

  4. hio: Use ExtendBufferedRelBy() to extend tables more efficiently

  5. heapam: Pass number of required pages to RelationGetBufferForTuple()

  6. Convert many uses of ReadBuffer[Extended](P_NEW) to ExtendBufferedRel()

  7. Use ExtendBufferedRelTo() in {vm,fsm}_extend()

  8. bufmgr: Introduce infrastructure for faster relation extension

  9. bufmgr: Support multiple in-progress IOs by using resowner

  10. bufmgr: Acquire and clean victim buffer separately

  11. bufmgr: Add Pin/UnpinLocalBuffer()

  12. bufmgr: Add some more error checking [infrastructure] around pinning

  13. Add smgrzeroextend(), FileZero(), FileFallocate()

  14. Don't initialize page in {vm,fsm}_extend(), not needed

  15. bufmgr: Remove buffer-write-dirty tracepoints

  16. hio: Release extension lock before initializing page / pinning VM

  17. bufmgr: Fix undefined behaviour with, unrealistically, large temp_buffers

  18. Fix memory leak and inefficiency in CREATE DATABASE ... STRATEGY WAL_LOG

  19. pgstat: Track more detailed relation IO statistics

  20. Use unnamed POSIX semaphores on Cygwin.

  21. Include RelFileLocator fields individually in BufferTag.