From: | Jeff Davis <pgsql(at)j-davis(dot)com> |
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To: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Memory-Bounded Hash Aggregation |
Date: | 2019-07-04 01:07:46 |
Message-ID: | f841a13aff32b0c2771e645e32a7a621d7efce42.camel@j-davis.com |
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Lists: | pgsql-hackers |
On Mon, 2019-07-01 at 12:13 -0700, Jeff Davis wrote:
> This is for design review. I have a patch (WIP) for Approach 1, and
> if
> this discussion starts to converge on that approach I will polish and
> post it.
WIP patch attached (based on 9a81c9fa); targeting September CF.
Not intended for detailed review yet, but it seems to work in enough
cases (including grouping sets and JIT) to be a good proof-of-concept
for the algorithm and its complexity.
Initial performance numbers put it at 2X slower than sort for grouping
10M distinct integers. There are quite a few optimizations I haven't
tried yet and quite a few tunables I haven't tuned yet, so hopefully I
can close the gap a bit for the small-groups case.
I will offer more details soon when I have more confidence in the
numbers.
It does not attempt to spill ARRAY_AGG at all yet.
Regards,
Jeff Davis
Attachment | Content-Type | Size |
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hashagg-20190703.patch | text/x-patch | 46.4 KB |
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