Re: patch: fix performance problems with repated decomprimation of varlena values in plpgsql

From: Andrew Dunstan <andrew(at)dunslane(dot)net>
To: Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
Cc: PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, Robert Haas <robertmhaas(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Subject: Re: patch: fix performance problems with repated decomprimation of varlena values in plpgsql
Date: 2010-11-22 12:55:54
Message-ID: 4CEA685A.6030203@dunslane.net
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On 11/22/2010 07:46 AM, Pavel Stehule wrote:
> Hello
>
> this patch remove a multiple detoasting of varlena values in plpgsql.
>
> It is usable mainly for iteration over longer array directly loaded
> from relation.
>
> It's doesn't have a impact on semantic or behave - it's just eliminate
> some performance trap.
>
> sample: table 10000 rows one column with array with 1000 string fields:
>
> patched pl time: 6 sec
> unpatched pl time: 170 sec
>

Since you haven't told us exactly how you tested this it's hard to gauge
the test results.

cheers

andrew

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