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

Peter Geoghegan <pg@bowt.ie>

From: Peter Geoghegan <pg@bowt.ie>

To: Alvaro Herrera <alvherre@2ndquadrant.com>

Cc: Jeff Davis <pgsql@j-davis.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>

Date: 2020-09-14T22:39:08Z

Lists: pgsql-hackers

On Mon, Sep 14, 2020 at 3:24 PM Alvaro Herrera <alvherre@2ndquadrant.com> wrote:
> I don't understand this patch.  Or maybe I should say I don't understand
> the code you're patching.  Why isn't the correct answer *always*
> nBlocksWritten?  The comment in LogicalTapeSet says:

I think that they are an exact match in practice (i.e. nBlocksWritten
== nBlocksAllocated), given when and how we call
LogicalTapeSetBlocks().

-- 
Peter Geoghegan

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