On Mon, May 11, 2020 at 09:15:43PM -0400, Bruce Momjian wrote:
> On Mon, May 11, 2020 at 05:33:40PM -0700, Peter Geoghegan wrote:
> > On Mon, May 11, 2020 at 5:14 PM Bruce Momjian <bruce@momjian.us> wrote:
> > > Agreed. How is this?
> > >
> > > This allows efficient btree indexing of low cardinality columns.
> > > Users upgrading with pg_upgrade will need to use REINDEX to make use of
> > > this feature.
> >
> > I still think that the release notes should say that the key is only
> > stored once, while TIDs that identify table rows are stored together
> > as an array. Everything that's helpful (or harmful) about the feature
> > happens as a consequence of that. This isn't hard to grasp
> > intuitively, and is totally in line with how things like Oracle bitmap
> > indexes are presented to ordinary users.
>
> I still don't think these details belong in the release notes.
OK, I was able to add some of it cleanly:
This allows efficient btree indexing of low cardinality columns by
storing duplicate keys only once. Users upgrading with pg_upgrade
will need to use REINDEX to make use of this feature.
--
Bruce Momjian <bruce@momjian.us> https://momjian.us
EnterpriseDB https://enterprisedb.com
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