Re: index / sequential scan problem

On 17/07/2003 12:13 Fabian Kreitner wrote:
> That is what I read too and is why Im confused that the index is indeed
> executing faster. Can this be a problem with the hardware and/or
> postgress installation?


It's more likely that the OS has most of the data cached after the first
query and so doesn't need to re-read that data from disk when you retry
the query with seq scan disabled. Try something like this:

set enable_seqscan to true;
explain analyze ......
set enable_seqscan to false;
explain analyze ......
set enable_seqscan to true;
explain analyze ......

I expect you will find that the third query is also a lot faster that the
first query.

HTH

--
Paul Thomas
+------------------------------+---------------------------------------------+
| Thomas Micro Systems Limited | Software Solutions for the Smaller
Business |
| Computer Consultants         |
http://www.thomas-micro-systems-ltd.co.uk   |
+------------------------------+---------------------------------------------+