Horton

Re: Trouble with hashagg spill I/O pattern and costing

Jeff Davis <pgsql@j-davis.com>

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From: Jeff Davis <pgsql@j-davis.com>
To: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Cc: pgsql-hackers@postgresql.org
Date: 2020-05-21T19:40:23Z
Lists: pgsql-hackers 
On Thu, 2020-05-21 at 21:13 +0200, Tomas Vondra wrote:
> 1) Instead of assigning the pages one by one, we can easily extend
> the
> API to allow getting a range of blocks, so that we don't need to call
> ltsGetFreeBlock in a loop. Instead we could call ltsGetFreeBlockRange
> with the requested number of blocks.

ltsGetFreeBlock() just draws one element from a minheap. Is there some
more efficient way to get many elements from a minheap at once?

>  And we could keep just a min/max
> of free blocks, not an array with fixed number of elements.

I don't quite know what you mean. Can you elaborate?

Regards,
	Jeff Davis

Commits

  1. Use CP_SMALL_TLIST for hash aggregate

  2. Avoid fragmentation of logical tapes when writing concurrently.