| From: | "Merlin Moncure" <merlin(dot)moncure(at)rcsonline(dot)com> | 
|---|---|
| To: | "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> | 
| 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 21:01:34 | 
| Message-ID: | 6EE64EF3AB31D5448D0007DD34EEB3417DD731@Herge.rcsinc.local | 
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| Lists: | pgsql-performance | 
> mark(at)mark(dot)mielke(dot)cc writes:
> > I've been trying to figure out whether null values are indexed or
not
> from
> > the documentation. I was under the impression, that null values are
not
> > stored in the index.
> 
> 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.  The only way I could
query for/against null values was to convert to bool via function.
However I did a partial exclusion on a 1% non null value really big
table and index size dropped as expected.
Merlin
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