Date: Thu, 21 May 2020 23:02:32 +0200
From: Tomas Vondra <tomas.vondra@2ndquadrant.com>
To: Jeff Davis <pgsql@j-davis.com>
Cc: pgsql-hackers@postgresql.org
Subject: Re: Trouble with hashagg spill I/O pattern and costing
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On Thu, May 21, 2020 at 12:40:23PM -0700, Jeff Davis wrote:
>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?
>

Ah, I forgot there's and internal minheap thing - I thought we're just
incrementing some internal counter or something like that, but with the
minheap we can't just get a range of blocks. So just disregard that,
you're right we need the array.


regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services