Re: Why hash indexes suck

From: "Zeugswetter Andreas SB SD" <ZeugswetterA(at)spardat(dot)at>
To: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "Jeff Davis" <jdavis-pgsql(at)empires(dot)org>
Cc: <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Why hash indexes suck
Date: 2004-06-07 08:04:50
Message-ID: 46C15C39FEB2C44BA555E356FBCD6FA40184D0F6@m0114.s-mxs.net
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> We could safely sort on the hash value, but I'm not sure how effective
> that would be, considering that we're talking about values that already
> hashed into the same bucket --- there's likely not to be very many
> distinct hash values there.

I think we can safely put that on the todo list.
The existing hash algorithm is very good. So I would on the
contrary beleive that only a few keys share a hash value per pagesized bucket.
For the equal keys case it does not matter since we want all of the rows anyways.
For the equal hash value case it would probably be best to sort by ctid.

TODO ?: order heap pointers inside hash index pages by hash value and ctid

Andreas

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