Skip site navigation (1) Skip section navigation (2)

Re: hash index improving v3

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Alex Hunsaker" <badalex(at)gmail(dot)com>
Cc: "Zdenek Kotala" <Zdenek(dot)Kotala(at)sun(dot)com>, "Xiao Meng" <mx(dot)cogito(at)gmail(dot)com>, pgsql-patches(at)postgresql(dot)org, "Jonah H(dot) Harris" <jonah(dot)harris(at)gmail(dot)com>
Subject: Re: hash index improving v3
Date: 2008-09-05 01:45:53
Message-ID: 11525.1220579153@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
I wrote:
> You have the unique-versus-not dimension,

On second thought, actually not.  What we want to look at is the penalty
for false matches due to *distinct* key values that happen to have the
same hash codes.  Your test case for all-the-same is using all the same
key values, which means it'll hit the heap a lot, but none of those will
be wasted trips.

So what we need for testing is a few different key values that hash to
the same code.  Not sure about an easy way to find such.

			regards, tom lane

In response to

Responses

pgsql-hackers by date

Next:From: Alex HunsakerDate: 2008-09-05 01:51:14
Subject: Re: hash index improving v3
Previous:From: Tom LaneDate: 2008-09-05 01:13:18
Subject: Re: hash index improving v3

pgsql-patches by date

Next:From: Alex HunsakerDate: 2008-09-05 01:51:14
Subject: Re: hash index improving v3
Previous:From: Tom LaneDate: 2008-09-05 01:13:18
Subject: Re: hash index improving v3

Privacy Policy | About PostgreSQL
Copyright © 1996-2014 The PostgreSQL Global Development Group