Re: ANALYZE patch for review

Hi Tom,

Having been working with the PostGIS team to implement a custom analyze
routine for R-Tree selectivity, we have a question regarding the new
vacuum_delay_point() which is present in analyze.c. Is it the
responsibility of the programmers to remember to do a
vacuum_delay_point() before calling the fetch_func(), or would it be
better to move the vacuum_delay_point() into std_fetch_func()? It would
seem to make more sense that the throttling is done by PostgreSQL rather
than requiring programmers to have to remember to include the extra
function call before calling the fetch_func() themselves.

Many thanks,

Mark.

---

Mark Cave-Ayland
Webbased Ltd.
Tamar Science Park
Derriford
Plymouth
PL6 8BX
England

Tel: +44 (0)1752 764445
Fax: +44 (0)1752 764446

This email and any attachments are confidential to the intended
recipient and may also be privileged. If you are not the intended
recipient please delete it from your system and notify the sender. You
should not copy it or use it for any purpose nor disclose or distribute
its contents to any other person.

"Mark Cave-Ayland" <m(dot)cave-ayland(at)webbased(dot)co(dot)uk> writes:
> Having been working with the PostGIS team to implement a custom analyze
> routine for R-Tree selectivity, we have a question regarding the new
> vacuum_delay_point() which is present in analyze.c. Is it the
> responsibility of the programmers to remember to do a
> vacuum_delay_point() before calling the fetch_func(), or would it be
> better to move the vacuum_delay_point() into std_fetch_func()?

It's probably not really necessary to call vacuum_delay_point in the
analysis routine, unless you are contemplating extremely expensive
analysis. If you did have an expensive loop, would std_fetch_func
necessarily be called inside it? It seems inappropriate to me to put
vacuum_delay_point inside std_fetch_func --- it's the analysis
programmer's business to understand whether it must be called, and if
so where's an appropriate place.

regards, tom lane