From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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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 |
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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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