From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
cc: pgsql-hackers@lists.postgresql.org,
        Thomas Munro <thomas.munro@enterprisedb.com>,
        Andrew Gierth <andrew@tao11.riddles.org.uk>,
        Alexander Kuzmenkov <a.kuzmenkov@postgrespro.ru>
Subject: Re: Performance improvements for src/port/snprintf.c
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Comments: In-reply-to Andres Freund <andres@anarazel.de>
	message dated "Wed, 03 Oct 2018 08:52:07 -0700"
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Date: Wed, 03 Oct 2018 12:07:32 -0400
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Andres Freund <andres@anarazel.de> writes:
> FWIW, it seems that using a local buffer and than pstrdup'ing that in
> float8out_internal is a bit faster, and would probably save a bit of
> memory on average:
> float8out using sprintf via pg_double_to_string, pstrdup:
> 15370.774
> float8out using strfromd via pg_double_to_string, pstrdup:
> 13498.331

[ scratches head ... ]  How would that work?  Seems like it necessarily
adds a strlen() call to whatever we'd be doing otherwise.  palloc isn't
going to be any faster just from asking it for slightly fewer bytes.
I think there might be something wrong with your test scenario ...
or there's more noise in the numbers than you thought.

			regards, tom lane