| From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
|---|---|
| To: | Hannu Krosing <hannu(at)tm(dot)ee> |
| Cc: | Eric Ridge <ebr(at)tcdi(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Postgres + Xapian (was Re: fulltext searching via a |
| Date: | 2004-01-12 23:47:36 |
| Message-ID: | 200401122347.i0CNla928182@candle.pha.pa.us |
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| Lists: | pgsql-general pgsql-hackers |
Hannu Krosing wrote:
> Eric Ridge kirjutas R, 09.01.2004 kell 01:16:
>
> > Forgetting about composite indexes for a moment, is postgres even
> > capable of doing 2 index scans in this situation? Does it know how do
> > take the intersection of two scans?
>
> Not currently, but it has been in TODO for quite some time:
>
> * Use bitmaps to fetch heap pages in sequential order [performance]
> * Use bitmaps to combine existing indexes [performance]
And this the foundation of bitmapped indexes, as I understand it, and is
used for "star" joins, popular with data warehousing.
Rather than use those terms, I spelled out the actual behavior we want.
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Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
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