[udig-devel] Re: [Geotools-gt2-users] Poor performance using Filter with shapefile...

[Andrea Aime]

sebastien.piau at ingencys.net ha scritto:
...
> See the debug info :
> 
> [DEBUG_GeoCodageExcelWizard_16:47:04 453] Start 338 check feature 
> collection here
> [DEBUG_GeoCodageExcelWizard_16:47:04 484] End 338 check feature 
> collection here
> => 31ms to apply the filter and query.
> 
> 
> When I put this layer in Memory (By creating a a new Layer in udig with 
> MemoryDataStore) performances are much better!!
> 
> [DEBUG_GeoCodageExcelWizard_16:51:40 187] Start 338 check feature 
> collection here
> [DEBUG_GeoCodageExcelWizard_16:51:40 203] End 338 check feature 
> collection here
> => 16ms
> 
> I would like to know if such a difference is normal, and how way could 
> we reduce calculation time by other way than creating a new 'in memory" 
> layer?

Reading stuff from memory instead of disk is definitely faster, no doubt
about it, the disk is the slowest part of your pc.
Yet, the benchmarks above are useless, a matter of milliseconds can be
influenced too much by external stuff such as background running tasks
on your pc (mail checking, antivirus, whatever).

A good bench must take some tens of seconds to make sure. Anyway, the
result above won't change, if you have enough memory and do not do spatial
filters the memory data store will always be faster.
Postgis and other database will become faster than memory only if your
dataset is big and the database can use indexes to solve queries, otherwise
the extra machinery (network protocol, transaction management, and so on)
will definitely make those slower than a memory data store.

Cheers
Andrea Aime