Re: pg_index.indislossy

From: Hannu Krosing <hannu(at)tm(dot)ee>
To: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: pg_index.indislossy
Date: 2001-05-15 04:28:08
Message-ID: 3B00B058.DC71B061@tm.ee
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Bruce Momjian wrote:
>
> > Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> > > Is lossy and partial indexes the same?
> >
> > No.
> >
> > > I can't see how they were
> > > supposed to be used. The _only_ mention of this field I see in
> > > indexcmd.c, around line 132.
> >
> > You missed a few then --- the most critical being in createplan.c.
> >
> > AFAIK this is a working feature, and I am going to insist that you
> > keep your hands off it ...
>
> Really, it actually works? What are they?

rom the readme of contrib/intarray/README.intarray

This is an implementation of RD-tree data structure using GiST interface
of PostgreSQL. It has built-in lossy compression - must be declared
in index creation - with (islossy). Current implementation provides
index
support for one-dimensional array of int4's - gist__int_ops, suitable
for
small and medium size of arrays (used on default), and gist__intbig_ops
for
indexing large arrays (we use superimposed signature with length of 4096
bits to represent sets).

-----------------------
Hannu

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