[postgis-users] topology performance improvement purpose

[Jose Carlos Martinez]

On 03/05/2012 11:19, Sandro Santilli wrote:
> On Thu, May 03, 2012 at 12:13:58AM +0200, Jose Carlos Martinez Llario wrote:
>> i meant not the default schema in search_path but the first topology
>> working schema after public.
> In order for your idea to work reliably the topology schema
> must really be the first one, even before public. Or existance
> of an "edge" or "node" or "relation" or "face" or "edge_data"
> relation in public would break the functions.
>
> It's surely an interesting idea worth trying out.
>
> I've been thinking that we'd also want "internal"
> functions for use by other "external" ones, for the same
> performance reason (for example to reduce checks when
> the caller knows it already performed them).
>
> There could be such "internal" functions taking no topology
> name but rather assuming the topology schema is the first
> in search_path. But even changing single functions to do
> the search_path trick only internally might show up improvements.
>
> The testsuite for topology is pretty robust so any implementation
> should be easy to check for regressions. Of course there's no test
> for the presence of specially named tables in the public schema
> which we should add to prevent regressions like the above.
>
> Do you feel like producing performance tests ? Such tests should
> generate common cases of expensive datasets and run the functions
> over them, reporting timings of each run. Won't be easy to test
> "hot" runs with mutating functions...
I didnt check the testsuite for topology Sandro. I will look at it though.
Do you think its worth it to try to modify some topology functions for 
not using EXECUTE and do some performance tests?
If so, I will do when I have a while.


>
> Addressing each specific function in turn would likely help
> managing this process. Maybe starting from one that's known to
> hit often.
>
> --strk;
>
>> On 02/05/2012 23:58, Jose Carlos Martinez Llario wrote:
>>> Hi,
>>> wanted to share a though about improving the topology performance
>>> in postgis.
>>>
>>> Many of the functions are using EXECUTE instead of running
>>> directly select commands.
>>> In many cases this is need just because of the used of the schema
>>> name  of the topology primitive tables.
>>>
>>> I found between 4 and 10 times improving performance some
>>> sentences. I guessing it could be even better.
>>>
>>> My question is if an approach like the following makes sense:
>>>
>>> 1.- With one command we can make the current topology schema the
>>> default schema in search path,
>>> 2.- then working with topology
>>> 3.- Change search_path again when finishing the spatial analysis.
>>>
>>> (the parameter of the topology name in the functions should be
>>> ignored or removed)
>>> I know it requires a lot of changes but currently the performance
>>> of the persistent topology is too slow.
>>>
>>> if one do that many functions can be run without EXECUTE. Spatial
>>> analysis between different topologies is not possible which fits
>>> the procedure.
>>>
>>> What do you think Sandro?
>>>
>>> Regards,
>>> Jose
>>>
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-- 

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José Carlos Martínez Llario

Producción Cartográfica y SIG.
Dpto. Ingeniería Cartográfica.
Univ. Politécnica de Valencia.

E-mail: jomarlla at cgf.upv.es
Telf: 963877000 ext. 75599
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