Re: Bitmapscan changes

Simon Riggs wrote:
> On Mon, 2007-03-12 at 13:56 -0400, Tom Lane wrote:
>
>> At this point I'm feeling unconvinced that we want it at all.  It's
>> sounding like a large increase in complexity (both implementation-wise
>> and in terms of API ugliness) for a fairly narrow use-case --- just
>> how much territory is going to be left for this between HOT and bitmap
>> indexes?
>
> HOT and clustered indexes have considerable synergy. In many tests we've
> got +20% performance with them acting together. Neither one achieves
> this performance on their own, but together they work very well.

To clarify, Simon is talking about DBT-2 tests we run in November.
Clustered indexes don't require HOT per se, but on TPC-C the performance
benefit comes from reducing the amount of I/O on the stock table and
index, and that's a table that gets updated at a steady rate. Without
HOT, the updates will disorganize the table and the performance gain you
get from clustered indexes vanishes after a while.

--
   Heikki Linnakangas
   EnterpriseDB   http://www.enterprisedb.com