From: | Gregory Maxwell <gmaxwell(at)gmail(dot)com> |
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To: | Ron Peacetree <rjpeace(at)earthlink(dot)net> |
Cc: | "Jeffrey W(dot) Baker" <jwbaker(at)acm(dot)org>, pgsql-hackers(at)postgresql(dot)org, pgsql-performance(at)postgresql(dot)org |
Subject: | Re: [PERFORM] A Better External Sort? |
Date: | 2005-10-01 02:07:16 |
Message-ID: | e692861c0509301907r7f1cd5b8h8b2b1f3a85321313@mail.gmail.com |
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Lists: | pgsql-hackers pgsql-performance |
On 9/28/05, Ron Peacetree <rjpeace(at)earthlink(dot)net> wrote:
> 2= We use my method to sort two different tables. We now have these
> very efficient representations of a specific ordering on these tables. A
> join operation can now be done using these Btrees rather than the
> original data tables that involves less overhead than many current
> methods.
If we want to make joins very fast we should implement them using RD
trees. For the example cases where a join against a very large table
will produce a much smaller output, a RD tree will provide pretty much
the optimal behavior at a very low memory cost.
On the subject of high speed tree code for in-core applications, you
should check out http://judy.sourceforge.net/ . The performance
(insert, remove, lookup, AND storage) is really quite impressive.
Producing cache friendly code is harder than one might expect, and it
appears the judy library has already done a lot of the hard work.
Though it is *L*GPLed, so perhaps that might scare some here away from
it. :) and good luck directly doing joins with a LC-TRIE. ;)
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