Re: Default setting for enable_hashagg_disk - Mailing list pgsql-hackers

From Jeff Davis
Subject Re: Default setting for enable_hashagg_disk
Date
Msg-id 9f2c09bafc1452f42b8c4131f4f63b8687bd8b3d.camel@j-davis.com
Whole thread Raw
In response to Re: Default setting for enable_hashagg_disk  (Peter Geoghegan <pg@bowt.ie>)
List pgsql-hackers
On Sat, 2020-07-25 at 17:52 -0700, Peter Geoghegan wrote:
> BTW, your HLL patch ameliorates the problem with my extreme "sorted
> vs
> random input" test case from this morning [1] (the thing that I just
> discussed with Tomas). Without the HLL patch the sorted case had 2424
> batches. With the HLL patch it has 20. That at least seems like a
> notable improvement.

Committed.

Though I did notice some overhead for spilled-but-still-in-memory cases
due to addHyperLogLog() itself. It seems that it can be mostly
eliminated with [1], though I'll wait to see if there's an objection
because that would affect other users of HLL.

Regards,
    Jeff Davis

[1] 
https://www.postgresql.org/message-id/17068336d300fab76dd6131cbe1996df450dde38.camel@j-davis.com





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