From: | David Rowley <dgrowleyml(at)gmail(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Robert Haas <robertmhaas(at)gmail(dot)com>, Stephen Frost <sfrost(at)snowman(dot)net>, Andres Freund <andres(at)anarazel(dot)de>, Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com> |
Subject: | Re: Parallel Aggregates for string_agg and array_agg |
Date: | 2023-01-23 00:49:25 |
Message-ID: | CAApHDvq7ChY83NaCw9e8rP1jUd_hgVj=jespHFY56gA4TynnfA@mail.gmail.com |
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On Thu, 19 Jan 2023 at 20:44, David Rowley <dgrowleyml(at)gmail(dot)com> wrote:
> The attached agg_comparison_scalability.png shows the time it took to
> execute the query with 0 workers divided by the time for N workers,
> thus showing how many times the query was sped up with N workers. The
> scalability of the string_agg() appears slightly better than the sum()
> in this test due to the string_agg() query being slightly slower with
> 0 workers than the sum() version of the query. The sum query got 7.63x
> faster with 32 workers whereas the string_agg query beat that slightly
> with 7.67x faster than when the query was executed with parallelism
> disabled.
I was just looking at this again today and I noticed I messed up the
script and used the sum(b) query twice instead of the
string_agg(b::text, ',') query. oops.
I've attached the correct graphs this time. The scalability of
string_agg() is not quite as good as I reported before, but it's still
good. sum(b) with 32 workers with a new benchmark run I found to be
7.15x faster than with 0 parallel workers and string_agg(b::text, ',')
I found to be 6.49x faster with 32 workers than with 0 parallel
workers. This test showed that the string_agg query scaled better with
up to 6 workers before the scalability dropped below that of the
sum(b) query.
David
Attachment | Content-Type | Size |
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image/png | 71.3 KB | |
agg_comparison_scalability_v2.png | image/png | 77.8 KB |
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