[udig-devel] Memory Management in uDig?

[Jody Garnett]

Carsten Ehbrecht wrote:
> Hi,
>
> as far as i know, udig has the advantage that it has not to load all
> requested Features into memory.
>   
In general we try and load *no* features into memory.
> My question is: For which sources (shapefile, gml, wfs, postgis, ...)
> can this advantage be used?
>   
All of them do not load data into memory when displaying ...
- postgis, arcsde, oracle and so forth make use a "real" transaction so 
they don't use any memory on editing
- shapefile, gml, and other "simple" things make use of some memory to 
record what data you changed feature by feature
- wfs makes use of an in memory record of how your data was changed 
(series up add / remove / update commands) so it will use a little bit 
of memory the longer you edit
> Are only those Features loaded into memory which are currently visible on the map?
>   
Even the feature you currently see are not loaded into memory. You can 
run udig as a viewer with very low memory requirements.

The Table View is the only exception; it loads the entire layer into 
memory so you can scroll up and down in the table. That is usally fine; 
but working with some 3 million feature arcsde tables recently makes me 
worried ;-)  If you accidentally open the table view you can quickly 
change what is displayed in the top left before uDig pops memory.

Jody