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Re: [PERFORM] BUG #2737: hash indexing large table fails,while btree of same index works

From: "Simon Riggs" <simon(at)2ndquadrant(dot)com>
To: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: "Balazs Nagy" <bnagy(at)thenewpush(dot)com>,<pgsql-bugs(at)postgresql(dot)org>,<pgsql-performance(at)postgresql(dot)org>
Subject: Re: [PERFORM] BUG #2737: hash indexing large table fails,while btree of same index works
Date: 2006-11-11 08:17:54
Message-ID: 1163233075.3634.944.camel@silverbirch.site (view raw or flat)
Thread:
Lists: pgsql-bugspgsql-performance
On Fri, 2006-11-10 at 18:55 -0500, Tom Lane wrote:
> [ cc'ing to pgsql-performance because of performance issue for hash indexes ]
> 
> "Balazs Nagy" <bnagy(at)thenewpush(dot)com> writes:
> > Database table size: ~60 million rows
> > Field to index: varchar 127
> 
> > CREATE INDEX ... USING hash ...

I'd be interested in a performance test that shows this is the best way
to index a table though, especially for such a large column. No wonder
there is an 8GB index.

> One thought that comes to mind is to require hash to do an smgrextend()
> addressing the last block it intends to use whenever it allocates a new
> batch of blocks, whereupon md.c could adopt a saner API: allow
> smgrextend but not other calls to address blocks beyond the current EOF.

> Thoughts?

Yes, do it. 

-- 
  Simon Riggs             
  EnterpriseDB   http://www.enterprisedb.com



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