[postgis-users] Performance Help

Paul Ramsey pramsey at refractions.net
Thu Jul 26 09:43:01 PDT 2007

Just as a random performance tip, try reducing your random_page_cost 
from 4 to 2 in small increments (0.2?) and see if at any point you get a 
better plan and faster response.  Also, I assume you've given yourself 
enough work_mem and shared_buffers already.


Mark Cave-Ayland wrote:
> On Thu, 2007-07-26 at 11:51 +0000, Alan Cunnane wrote:
>> I have actually already looked at PG routing however because of the
>> constraints of this particular project I cannot use it. I have to use
>> SQL queries as I was attempting however it seems that the query runs
>> smoothly enough up until the 8th or 9th table is added to the join. Is
>> this my own fault in the query or is this just the performance of
>> Postgresql in handling a large number of joins? I do appreciate your
>> help and advice,
>> Alan
> Tricky :(
> I guess the only thing you can do in that case is check the query plans
> just before and just after the point at which the query plan
> deteriorates and try and spot the difference.
> Are you allowed to use stored procedures for your solution? Due to the
> recursive-type nature of some of the queries you will need, it may be
> possible to come up with something more efficient that way.
> HTH,
> Mark.


   Paul Ramsey
   Refractions Research
   pramsey at refractions.net
   Phone: 250-383-3022
   Cell: 250-885-0632

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