Re: Pluggable Indexes

On Wed, 21 Jan 2009, Simon Riggs wrote:

>
> On Wed, 2009-01-21 at 21:45 +0200, Heikki Linnakangas wrote:
>> Ron Mayer wrote:
>>> Early (2005)
>>> GIST indexes were very painful in production environments because vacuuming
>>> them held locks for a *long* time (IIRC, an hour or so on my database) on
>>> the indexes locking out queries. Was that just a shortcoming of the
>>> implementation, or was it a side-effect of them not supporting recoverability.
>>
>> The former.
>
> In the current way of thinking early-GIST would never have been
> committed and as a result we would not have PostGIS. Yes, early index
> implementations can be bad and they scare the hell out of me. That's
> exactly why I want to keep them out of core, so they don't need to be
> perfect, they can come with all sorts of health warnings.

I'm rather keen on Pg extendability, which allowed me and Teodor to
work on many extensions. Yes, first GiST we inherited from early
academic research and was more like a toy. We still have several TODO
items about GiST interface (incorporate SP-GiST).
I'm not sure about specific patch Simon advocate, but as soon as it
doesnot introduces any threat to the whole database cluster health
(for example, WAL spamming) I think we can apply it.
Other question, why don't improve GiST to allow support of more indexes ?
bitmap indexes could be implemented usin g GiST.

Regards,
Oleg
_____________________________________________________________
Oleg Bartunov, Research Scientist, Head of AstroNet (www.astronet.ru)
Sternberg Astronomical Institute, Moscow University, Russia
Internet: oleg(at)sai(dot)msu(dot)su, http://www.sai.msu.su/~megera/
phone: +007(495)939-16-83, +007(495)939-23-83