[Maposmatic-dev] Re: PostGIS help for MapOSMatic

[Jean-Christophe Arnu]

Hi Thomas,
could you run the (long running) queries with explain/explain analyze
and post the results on the wiki ?

Clue: EXPLAIN SELECT ...;
or EXPLAIN ANALYZE SELECT ...;

The information given by explain are quite useful to optimize queries.

Thanks a lot for this actions.

2010/2/27 Thomas Petazzoni <address@hidden>:
> Hi Vincent, Jean-Christophe, Guilhem and Sébastien,
>
> [ This message is CC'ed to the development mailing list of MapOSMatic,
>  which is why I'm writing to you in english. Please keep the list in
>  the CC list even if you're not subscribed. I'll moderate your
>  messages manually. Thanks! ]
>
> I'm writing to you concerning a PostgreSQL/PostGIS request optimization
> problem we have in MapOSMatic (http://www.maposmatic.org). The request
> in question is the one that gives us the list of the streets and the
> squares they intersect for a given city.
>
> Currently, for a city like Toulouse, the request takes 4 minutes and 39
> seconds, but our experiment show that it could be optimized down to 3.2
> seconds. But we don't know exactly how to generalize our experiments of
> optimization.
>
> Inside of writing a long e-mail, I've written a detailed explanation of
> the request, the problem and the analysis we've done so far at
> http://wiki.maposmatic.org/doku.php?id=dev:request_optimization.
>
> If you have the time, could you have a look and tell us what we are
> doing wrong ? Solving this problem would probably allow us to limit the
> load on the server and to generate maps for larger cities. Of course,
> if you need details about the request or the environment, don't
> hesitate.
>
> Thanks a lot for your help,
>
> Thomas
> --
> Thomas Petazzoni                         http://thomas.enix.org
> Promouvoir et défendre le Logiciel Libre http://www.april.org
> Logiciels Libres à Toulouse              http://www.toulibre.org
>



-- 
Jean-Christophe Arnu