[postgis-users] Benshmark postgis

Arnaud Vandecasteele arnaud.sig at gmail.com
Fri Nov 26 00:38:09 PST 2010

I understand better the interest of the Gis Index !  Thank you for your answer.
I do not want to evaluate the postgis vs other database, just the time
the queries will take for 1000 10 000 or more objects.
The use case will be this one :
We have several thousands of vessels and every 5 seconds I must do a
query to check if they are or not in a dangerous area?



On Fri, Nov 26, 2010 at 9:26 AM, strk <strk at keybit.net> wrote:
> On Fri, Nov 26, 2010 at 09:15:27AM +0100, Arnaud Vandecasteele wrote:
>> Thanks you for your answers.
>> I can understand your objections but how can I make this process better ?
>> Also, my tests gave me some strange results.
>> For the first set, I did the process explain before without a gis index (gist).
>> And for the seconde one I built a gis index.
>> I was expected better result for the second set, but it hasn't been
>> the case. Even sometimes it took me more times than without an index.
>> Do you know what could explain this behaviour ?
> Show the numbers!
> When you have an index the planner has to take a decision as to
> whether or not to use the index. This decision may explain an overhead
> you're seeing. If it chooses to NOT use the index the additional time
> spent in deciding will be clear. If it chooses to use the index then
> the speed difference can be due to other things.
> First, having just a few geoms (world countries) doesn't really show
> much advantage of the index.
> Second, having countries spannign the whole world (have bounding boxes
> shown on a map to see) doesn't make the index very efective (still finds
> many candidates).
> Your procedure is fine to check how good postgis is vs. others
> _given_the_exactly_same_input_
> I suggest making the points predictable too rather than rendom, if
> you're aiming at this kind of comparison.
> If you want to evaluate something else make it clear what the goal is.
> --strk;
>  ()   Free GIS & Flash consultant/developer
>  /\   http://strk.keybit.net/services.html
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Van De Casteele Arnaud
Mines Paris Tech - CRC
0698 24 25 29
SIG - WebMapping - SOLAP - BI - GeoCollaboration

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