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Re: 8.x index insert performance

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Merlin Moncure" <merlin(dot)moncure(at)rcsonline(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org,"Kelly Burkhart" <kelly(at)tradebotsystems(dot)com>
Subject: Re: 8.x index insert performance
Date: 2005-10-31 21:08:12
Message-ID: 18970.1130792892@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-performance
"Merlin Moncure" <merlin(dot)moncure(at)rcsonline(dot)com> writes:
>> You're mistaken, at least with regard to btree indexes.

> hmm. I tried several different ways to filter/extract null values from
> an indexed key and got a seq scan every time.

I said they were stored, not that you could query against them ;-)
IS NULL isn't considered an indexable operator, mainly because it's
not an operator at all in the strict sense of the word; and our index
access APIs only support querying on indexable operators.

The reason they're stored is that they have to be in order to make
multi-column indexes work right.  I suppose we could special-case
single-column indexes, but we don't.  In any case, it's more likely
that someone would one day get around to making IS NULL an indexable
operator than that we'd insert a special case like that.

			regards, tom lane

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