Re: Why hash indexes suck - Mailing list pgsql-hackers

From Bruce Momjian
Subject Re: Why hash indexes suck
Date
Msg-id 200406100335.i5A3Z4w07634@candle.pha.pa.us
Whole thread Raw
In response to Re: Why hash indexes suck  ("Zeugswetter Andreas SB SD" <ZeugswetterA@spardat.at>)
Responses Re: Why hash indexes suck  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-hackers
Added to TODO:
* Order heap pointers on hash index pages by hash value and ctid

---------------------------------------------------------------------------

Zeugswetter Andreas SB SD wrote:
> 
> > 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
> 
> ---------------------------(end of broadcast)---------------------------
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--  Bruce Momjian                        |  http://candle.pha.pa.us pgman@candle.pha.pa.us               |  (610)
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