Re: Execution Plan Cost

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.Vargas@cl.cam.ac.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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