Re: Macro customizable hashtable / bitmapscan & aggregation perf

From: Andres Freund <andres(at)anarazel(dot)de>
To: Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Macro customizable hashtable / bitmapscan & aggregation perf
Date: 2016-10-11 00:46:22
Message-ID: 20161011004622.5kkvlwghm4yvg4id@alap3.anarazel.de
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Hi,

On 2016-10-11 02:38:26 +0200, Tomas Vondra wrote:
> Yes, I've done a bunch of TPC-H and TPC-DS tests on the patch, but it took
> quite a bit of time. These tests were done on a fairly small machine (the
> usual i5-2500k with 8GB of RAM), with only 1GB data sets for both
> benchmarks, to keep it completely in memory as I presume once we start
> hitting I/O, it becomes the dominant part.

Thanks!

> TPC-DS (tpcds.ods)
> ------------------
>
> In this case, I'd say the results are less convincing. There are quite a few
> queries that got slower by ~10%, which is well above - for example queries
> 22 and 67. There are of course queries that got ~10% faster, and in total
> the patched version executed more queries (so overall the result is slightly
> positive, but not significantly).

That's interesting. I wonder whether that's plan changes just due to the
changing memory estimates, or what's causing that. I'll look into it.

Greetings,

Andres Freund

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