Re: GIN, partial matches, lossy bitmaps

On Thu, 5 Mar 2009, Robert Haas wrote:

> On Thu, Mar 5, 2009 at 6:35 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Attached is the remainder of the patch with relatively minor fixes.
>> The main change I made is to get rid of the changes in gincostestimate;
>> I agree with Robert that it's probably inappropriate to consider the
>> current pending-list size during planning.  I haven't really reviewed
>> any of the rest of it; this is just to have a clean patch against HEAD.
>
> The changes to config.sgml are not good English and contain
> typographical errors. It could also be a bit more informatiave, maybe
> something like:
>
> This parameter also specifies the number of insert or updated tuples
> needed to trigger <command>VACUUM</> on a <acronym>GIN</acronym>
> index. <acronym>GIN</acronym> indexes require <command>VACUUM</>
> after insert or update operations because newly inserted tuples are
> initially stored in an unsorted pending list.

thanks, will update docs.

>
> I still think removing index scans entirely is short-sighted - but I
> may be outvoted (then again, no one other than Tom has really
> expressed an opinion one way or the other, and I initially agreed with
> him until I thought about the performance aspects some more).

I'm also wonder if we're on the right way, since the only serious
issue with indexscan was possible problem with slaves, but read-only slaves
delayed to 8.5, so this is not an issue now. In 8.5 development cycle we'll
certainly return to this issue, so why do we disable index scan for 8.4 ?

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