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Re: Reviewing new index types (was Re: [PATCHES] Updated bitmap indexpatch)

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Simon Riggs" <simon(at)2ndquadrant(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Reviewing new index types (was Re: [PATCHES] Updated bitmap indexpatch)
Date: 2007-07-23 21:19:28
Message-ID: 15822.1185225568@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
"Simon Riggs" <simon(at)2ndquadrant(dot)com> writes:
> ... BMI is not useful at all
> for PKs, whilst GIT is specifically designed to handle them.

This seems a strange statement, because GIT doesn't look particularly
efficient for unique indexes AFAICS.  In the worst case you'd have to
look individually at each tuple on a heap page to check for uniqueness
conflict (no binary search, because you couldn't assume they are
ordered).

> B-TREE INDEXES (Integers) 

> Rows/value	Best time	Size in blocks
> 10000000	49s		21899
> 1000000		49s		21899
> 100000		49s		21899
> 10000		47s		21899
> 1000		43s		21899
> 100		38s		21899
> 10		38s		21899
> 1		33s		21899

Surely the GIT code failed to kick in at all here?  That's just about
exactly the index size I'd expect for 10 million integers with the
existing btree code (at least when MAXALIGN=4).

			regards, tom lane

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