From: | Luis Vargas <Luis(dot)Vargas(at)cl(dot)cam(dot)ac(dot)uk> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Execution Plan Cost |
Date: | 2008-05-14 13:50:58 |
Message-ID: | Prayer.1.2.0pre.0805141450580.15929@hermes-1.csi.cam.ac.uk |
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Lists: | pgsql-hackers |
The read-only plan of the query (SELECT $1 > 5) is prepared, so there is
not parsing or planning. Any insight into what operations account for the
executor startup/shutdown time?
Thanks a lot,
Luis Vargas
On May 8 2008, Tom Lane wrote:
>Luis Vargas <Luis(dot)Vargas(at)cl(dot)cam(dot)ac(dot)uk> writes:
>> At the backend, I'm measuring the cost of executing (via
>> SPI_execute_plan) the read-only plan of a simple query with no reference
>> to tables. E.g. simpleplan(int) AS SELECT $1 > 5
>
>> Executing this plan via SPI_execute takes around 70% more time than
>> directly executing the relevant operator function (int4gt) and using
>> DatumGetBool.
>
>Only that much? I'd have expected it to be several hundred times
>slower, considering that int4gt is an utterly trivial function and
>executor startup/shutdown is a fairly heavyweight operation.
>
> regards, tom lane
>
--
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