Richard --

 You might post the results of "EXPLAIN ANALYZE <your SQL here>;" ... be sure 
to run it in a transaction if you want to be able roll it back. Perhaps try 
"EXPLAIN <your SQL>;" first as it is faster, but EXPLAIN ANALYZE shows what the 
planner is doing.

You wrote:



> 
> P.S. Sometimes, some queries seem to benefit from being cancelled and then 
> immediately
> re-started. As there are being run in a transaction, I can't see how this 
> could make a difference.
> Am I missing anything obvious?  Occasionally, a re-start of postgresql-8.4l 
> itself seems to help.

This may be the result of caching of the desired rows, either by PostgreSQL or 
by your operating system. The rollback wouldn't effect this -- the rows are 
already in memory and not on disk waiting to be grabbed -- much faster on all 
subsequent queries.

HTH,

Greg Williamson


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