Re: Partition insert trigger using C language

On 11.01.2013 12:36, Matheus de Oliveira wrote:
> On Fri, Jan 11, 2013 at 8:19 AM, Heikki Linnakangas<hlinnakangas(at)vmware(dot)com
>> wrote:
>
>> One thing that caught my eye:
>>
>> CREATE OR REPLACE FUNCTION partition_insert_trigger_spi()
>>> RETURNS trigger
>>> LANGUAGE C
>>> VOLATILE STRICT
>>> AS 'partition_insert_trigger_spi'**,'partition_insert_trigger_**spi'
>>> SET DateStyle TO 'ISO';
>>
>> Calling a function with SET options has a fair amount of overhead, to
>> set/restore the GUC on every invocation. That should be avoided in a
>> performance critical function like this.
>
> I (stupidly) used SPI_getvalue [1] and expected it to always return as
> YYYY-MM-DD, but them I remembered it would do that only with DateStyle=ISO.
>
> But the truth is that I couldn't see any overhead, because the function was
> without that on my first tests, and after that I saw no difference on the
> tests.

Oh, ok then. I would've expected it to make a measurable difference.

> I think I should use SPI_getbinvalue instead, but I don't know how
> to parse the result to get year and month, any help on that?

The fastest way is probably to use j2date like date_out does:

DateADT date = DatumGetDateADT(x)
int year, month, mday;

if (DATE_NOT_FINITE(date))
elog(ERROR, "date must be finite");
j2date(date + POSTGRES_EPOCH_JDATE, &year, &month, &mday);

- Heikki