| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Teodor Sigaev <teodor(at)sigaev(dot)ru> |
| Cc: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, Reid Thompson <Reid(dot)Thompson(at)ateb(dot)com>, pgsql-general(at)postgresql(dot)org |
| Subject: | Re: If an index is based on 3 columns will a query using two of the columns utilize the index? |
| Date: | 2005-09-12 16:39:49 |
| Message-ID: | 22924.1126543189@sss.pgh.pa.us |
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| Lists: | pgsql-general |
Teodor Sigaev <teodor(at)sigaev(dot)ru> writes:
> GiST may work with any subset of index columns too. Even in existing code I
> don't see any problem except NULL in a first column. GiST doesn't store tuples
> with leading NULL value (gist.c lines 174, 326), so index doesn't contained them.
Well, that's exactly the problem :-(. Or at least one of the problems;
the other being what you'd use as search key to find such tuples.
> After our work about WAL-lization GiST, it may work with "invalid"
> tuples (possibly occured after crash recovery), so itsn't a big deal
> to add support NULL in a first column. But freeze date is
> outdated... Should I add or leave it to 8.2?
Too late for 8.1 I'd say --- this definitely sounds like a new feature
rather than a bug fix.
regards, tom lane
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