On 21 December 2015 at 12:54, Robert Haas <robertmh...@gmail.com> wrote:

> On Thu, Jul 9, 2015 at 4:49 PM, Jeff Janes <jeff.ja...@gmail.com> wrote:
> > Is there anything in the below section which has been been implemented or
> > rendered irrelevant by BRIN indexes?
> >
> > https://wiki.postgresql.org/wiki/Todo#Indexes
> >
> > "Consider smaller indexes that record a range of values per heap page,
> > rather than having one index entry for every heap row"
> [ catching up on old threads ]
> BRIN is exactly this, isn't it?  Well, moreso: it's a range of values
> for a range of heap pages.

It's close, but not the same.

BRIN is a summary index and so could never support uniqueness.

It's also possible to have an index type that has a precise TID entry, yet
a more compact format, which would then allow unique values. This would be
similar to the way SQLServer compresses primary key indexes.

Simon Riggs                http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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