Re: logtape.c stats don't account for unused "prefetched" block numbers

Jeff Davis <pgsql@j-davis.com>

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From: Jeff Davis <pgsql@j-davis.com>

To: Peter Geoghegan <pg@bowt.ie>, Alvaro Herrera <alvherre@2ndquadrant.com>

Cc: PostgreSQL Hackers <pgsql-hackers@postgresql.org>

Date: 2020-09-08T17:27:06Z

Lists: pgsql-hackers

Attachments

sort-no-prealloc.patch (text/x-patch) patch

On Sat, 2020-09-05 at 12:03 -0700, Peter Geoghegan wrote:
> We should totally disable the preallocation stuff for external sorts
> in any case. External sorts are naturally characterized by relatively
> large, distinct batching of reads and writes -- preallocation cannot
> help.

Patch attached to disable preallocation for Sort.

I'm still looking into the other concerns.

Regards,
	Jeff Davis

Commits

Change LogicalTapeSetBlocks() to use nBlocksWritten.
- 6e146a663536 13.0 landed
- c8aeaf3ab31e 14.0 landed
HashAgg: release write buffers sooner by rewinding tape.
- 42a46f5a76ec 13.0 landed
- 3bd35d4f516a 14.0 landed
logtape.c: do not preallocate for tapes when sorting
- 93106d71a18a 13.0 landed
- 075896496394 14.0 landed
Fix bogus MaxAllocSize check in logtape.c.
- 4a4f3bf983b4 13.0 landed
- 0852006a946a 14.0 landed
Avoid fragmentation of logical tapes when writing concurrently.
- 896ddf9b3cd7 13.0 cited
Logical Tape Set: use min heap for freelist.
- c02fdc922301 13.0 cited
Don't create "holes" in BufFiles, in the new logtape code.
- 7ac4a389a7db 10.0 cited