I see your point, although newly-created BasicFeatures aren't really an issue - they are always dirty by definition. It's just features which have had their attributes modified which are the problem.
I'm not totally crazy about this MutableBasicFeature/BasicFeature dichotomy, but it might be workable. You would have to flip BFs to MBFs when they were written out, since they would then become clean again. I think I'd prefer a scheme where the container kept track of which features have been modified, and leave features as simple value objects. I believe this is what GeoTools does. Can anyone confirm that before I go digging through their codebase? Larry Becker wrote: > > Perhaps you could extend BasicFeature to be a MutableBasicFeature, and > this is the concrete class that would be used by Writeable DataStores. > > > This is a good idea, but tough to implement. A search for "new > BasicFeature" found 80 matches in the project. The fact is that most > tools create BasicFeatures. Now perhaps, if we are clever, we can use > that to our advantage. Hmm... > > Larry > > On Thu, Apr 23, 2009 at 6:16 PM, Martin Davis <mbda...@refractions.net > <mailto:mbda...@refractions.net>> wrote: > > Perhaps you could extend BasicFeature to be a MutableBasicFeature, and > this is the concrete class that would be used by Writeable DataStores. > Only MutableBasicFeature would incur the overhead of tracking changes. > Whether the DataStore is writeable could be determined dynamically as > well (ie by user input when layer is created). There are a lot of use > cases where the writable aspect isn't needed. > > If it was me, I would still prefer the simpler single boolean > dirty flag > (although I would probably opt for still implementing > MutableBasicFeature, in case there was more behaviour that needed > to be > added down the road.) > > If I get a chance I'll try and see what GeoTools does here - they must > have this same problem. > > Larry Becker wrote: > > I think the other developers need to understand that the cost of > > supporting per-feature modified status will be a per-feature cost of > > (size of int) * number of attributes. I'm not sure I made that > > clear. Currently the memory cost is for all features on all layers. > > Perhaps there is needed a way to opt-in to this cost and > functionality > > at layer creation time. Hmm... > > > > Larry > > > > On Thu, Apr 23, 2009 at 4:53 PM, Martin Davis > <mbda...@refractions.net <mailto:mbda...@refractions.net> > > <mailto:mbda...@refractions.net > <mailto:mbda...@refractions.net>>> wrote: > > > > I guess the memory issue might be moot for DataStore-based > datasets > > anyway, since the whole point is to only keep in memory what is > > currently displayed on the screen. > > > > But simpler is always better! Alarm bells start ringing for > me when I > > see counts being used - the semantics seems like they must > be more > > complicated than a simple flag. > > > > Larry Becker wrote: > > > > > > > I agree that a mechanism to reset the modified status is > needed, > > > especially after the changes to the layer have been > flushed to the > > > database. I'll add this to BasicFeature. > > > > > > Your comment about carrying around state data after it is > needed is > > > reasonable. The code could check for modified on-the-fly > while > > it is > > > incrementing the attribute mod count and if it is greater > than one, > > > set a boolean instead and dispose of the array of ints. > You would > > > lose the ability to determine individual attribute mods > (not sure if > > > it is needed), however you would only save memory in modified > > records > > > which wouldn't usually be very much. > > > > > > I was hoping someone would come up with a clever hack that > wouldn't > > > require the int array. All of the optimizations that I have > > > considered break in one case or another. > > > > > > BTW, if you really want to save memory on attribute storage, I > > have a > > > number of questionable schemes that load attributes on an > as-needed > > > basis. :-) SkyJUMP even has an optimization were layers that > > aren't > > > visible are not loaded into memory until you make them > visible, > > > although it doesn't go as far as removing them when you > make them > > > invisible. Of course the most famous attribute > memory-saving scheme > > > is Michael's permgen attribute string scheme for dbf files. > > That one > > > saves a ton of memory on typically redundant data, until > you run out > > > of permgen memory. > > > > > > Larry > > > > > > On Thu, Apr 23, 2009 at 4:06 PM, Martin Davis > > <mbda...@refractions.net <mailto:mbda...@refractions.net> > <mailto:mbda...@refractions.net <mailto:mbda...@refractions.net>> > > > <mailto:mbda...@refractions.net > <mailto:mbda...@refractions.net> > > <mailto:mbda...@refractions.net > <mailto:mbda...@refractions.net>>>> wrote: > > > > > > re Mutating Geometry in-place - JTS discourages this, but > > does not > > > prevent it. Sometimes people do this when they are > transforming > > > coordinates (eg. translation or affine transform).. > It's > > quite > > > possible that all the JUMP code is clean, however. In any > > case, this > > > will only be an issue if that particular function is used. > > > > > > re tracking modifications - how about providing a method > > that lets you > > > clear the modified flag? Then the feature can be > constructed as > > > necessary and then marked as clean. > > > > > > It seems heavyweight to carry around a set of data > which is only > > > really > > > of use during the construction phase of a Feature. To > avoid > > this, I'd > > > even suggest constructing a Feature as needed, then > creating > > a new > > > Feature from it via a constructor which sets the > modified flag > > > appropriately. Anything to avoid requiring more storage. > > > > > > How does GeoTools handle this? > > > > > > Larry Becker wrote: > > > > The tricky thing about modifications is not to find a > > record is > > > > modified just because you set the initial value. It > is only > > > modified > > > > if you set it more than once, otherwise all records > would > > be set as > > > > modified as soon as they are loaded. > > > > > > > > The next trick is to consider that you call setAttribute > > multiple > > > > times with different attribute indexes, so it is > necessary > > to track > > > > the changes to each one separately. > > > > > > > > Mutating Geometries in place is a concern. I have never > > seen code > > > > that does this, and certainly none of the edit tools or > > any plugins > > > > that use transactions do this, but it may be > possible. Could > > > you just > > > > modify the Coordinate.x and y values? I'll try to > construct a > > > > Beanshell test for this, but I doubt that this is a > > serious concern. > > > > All of the tools and plugins that I have tried so > far play by > > > the rules. > > > > > > > > Larry > > > > > > > > On Thu, Apr 23, 2009 at 2:12 PM, Martin Davis > > > <mbda...@refractions.net > <mailto:mbda...@refractions.net> <mailto:mbda...@refractions.net > <mailto:mbda...@refractions.net>> > > <mailto:mbda...@refractions.net > <mailto:mbda...@refractions.net> <mailto:mbda...@refractions.net > <mailto:mbda...@refractions.net>>> > > > > <mailto:mbda...@refractions.net > <mailto:mbda...@refractions.net> > > <mailto:mbda...@refractions.net > <mailto:mbda...@refractions.net>> > > > <mailto:mbda...@refractions.net > <mailto:mbda...@refractions.net> > > <mailto:mbda...@refractions.net > <mailto:mbda...@refractions.net>>>>> wrote: > > > > > > > > Larry, why do you use an int rather than a > boolean to flag > > > changed > > > > attributes? > > > > > > > > BTW, In order to track changes to Geometry > attributes > > > correctly, the > > > > JUMP codebase needs to be scrutinized to make > sure it > > isn't > > > mutating > > > > Geometries "in place". > > > > > > > > > > > > > > > > Larry Becker wrote: > > > > > Hi, > > > > > > > > > > As I mentioned in the other thread, before > the problem > > > of partial > > > > > database updates can be solved, we must first > be able to > > > > determine if > > > > > a Feature has been modified. This is not > currently > > > possible in > > > > all of > > > > > the JUMP variants that I am familiar with, > although > > Kosmo > > > may have > > > > > implemented it. > > > > > > > > > > The simplest way of implementing it that I can > see is to > > > modify > > > > > BasicFeature to include: > > > > > > > > > > private int[] attributeModCount; //this is a > parallel > > > array to > > > > > Object[] attributes > > > > > > > > > > Then it would be necessary to allocate the > > > attributeModCount array > > > > > when setAttributes(Object[] attributes) is called. > > > > > > > > > > In addition each time setAttribute(int > > attributeIndex, Object > > > > > newAttribute) is called, add the line of code: > > > > > > > > > > attributeModCount[attributeIndex]++ > > > > > > > > > > With these modifications we could then define: > > > > > > > > > > public boolean isFeatureModified() { > > > > > for (int i=0; i<attributeModCount.length; > i++) { > > > > > if (attributeModCount[i] > 1) //modified is > > defined as > > > > setting > > > > > an attribute more than once > > > > > return true; > > > > > } > > > > > return false; > > > > > } > > > > > > > > > > Would this work and does this seem like > something we > > should > > > > consider? > > > > > > > > > > regards, > > > > > Larry > > > > > -- > > > > > http://amusingprogrammer.blogspot.com/ > > > > > > > > > > > > > > > ------------------------------------------------------------------------ > > > > > > > > > > > > > > > > > > > > > ------------------------------------------------------------------------------ > > > > > > > > > > > > > > > > > > > > ------------------------------------------------------------------------ > > > > > > > > > > _______________________________________________ > > > > > Jump-pilot-devel mailing list > > > > > Jump-pilot-devel@lists.sourceforge.net > <mailto:Jump-pilot-devel@lists.sourceforge.net> > > <mailto:Jump-pilot-devel@lists.sourceforge.net > <mailto:Jump-pilot-devel@lists.sourceforge.net>> > > > <mailto:Jump-pilot-devel@lists.sourceforge.net > <mailto:Jump-pilot-devel@lists.sourceforge.net> > > <mailto:Jump-pilot-devel@lists.sourceforge.net > <mailto:Jump-pilot-devel@lists.sourceforge.net>>> > > > > <mailto:Jump-pilot-devel@lists.sourceforge.net > <mailto:Jump-pilot-devel@lists.sourceforge.net> > > <mailto:Jump-pilot-devel@lists.sourceforge.net > <mailto:Jump-pilot-devel@lists.sourceforge.net>> > > > <mailto:Jump-pilot-devel@lists.sourceforge.net > <mailto:Jump-pilot-devel@lists.sourceforge.net> > > <mailto:Jump-pilot-devel@lists.sourceforge.net > <mailto:Jump-pilot-devel@lists.sourceforge.net>>>> > > > > > > > https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel > > > > > > > > > > > > > -- > > > > Martin Davis > > > > Senior Technical Architect > > > > Refractions Research, Inc. > > > > (250) 383-3022 > > > > > > > > > > > > > > > > > > > ------------------------------------------------------------------------------ > > > > Crystal Reports - New Free Runtime and 30 > Day Trial > > > > Check out the new simplified licensign option > that enables > > > unlimited > > > > royalty-free distribution of the report > engine for > > > externally > > > > facing > > > > server and web deployment. > > > > http://p.sf.net/sfu/businessobjects > > > > _______________________________________________ > > > > Jump-pilot-devel mailing list > > > > Jump-pilot-devel@lists.sourceforge.net > <mailto:Jump-pilot-devel@lists.sourceforge.net> > > <mailto:Jump-pilot-devel@lists.sourceforge.net > <mailto:Jump-pilot-devel@lists.sourceforge.net>> > > > <mailto:Jump-pilot-devel@lists.sourceforge.net > <mailto:Jump-pilot-devel@lists.sourceforge.net> > > <mailto:Jump-pilot-devel@lists.sourceforge.net > <mailto:Jump-pilot-devel@lists.sourceforge.net>>> > > > > <mailto:Jump-pilot-devel@lists.sourceforge.net > <mailto:Jump-pilot-devel@lists.sourceforge.net> > > <mailto:Jump-pilot-devel@lists.sourceforge.net > <mailto:Jump-pilot-devel@lists.sourceforge.net>> > > > <mailto:Jump-pilot-devel@lists.sourceforge.net > <mailto:Jump-pilot-devel@lists.sourceforge.net> > > <mailto:Jump-pilot-devel@lists.sourceforge.net > <mailto:Jump-pilot-devel@lists.sourceforge.net>>>> > > > > > > https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel > > > > > > > > > > > > > > > > > > > > -- > > > > http://amusingprogrammer.blogspot.com/ > > > > > > > > > > ------------------------------------------------------------------------ > > > > > > > > > > > > > > > ------------------------------------------------------------------------------ > > > > Crystal Reports - New Free Runtime and 30 Day Trial > > > > Check out the new simplified licensign option that > enables > > unlimited > > > > royalty-free distribution of the report engine for > > > externally facing > > > > server and web deployment. > > > > http://p.sf.net/sfu/businessobjects > > > > > > > > > > ------------------------------------------------------------------------ > > > > > > > > _______________________________________________ > > > > Jump-pilot-devel mailing list > > > > Jump-pilot-devel@lists.sourceforge.net > <mailto:Jump-pilot-devel@lists.sourceforge.net> > > <mailto:Jump-pilot-devel@lists.sourceforge.net > <mailto:Jump-pilot-devel@lists.sourceforge.net>> > > > <mailto:Jump-pilot-devel@lists.sourceforge.net > <mailto:Jump-pilot-devel@lists.sourceforge.net> > > <mailto:Jump-pilot-devel@lists.sourceforge.net > <mailto:Jump-pilot-devel@lists.sourceforge.net>>> > > > > > https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel > > > > > > > > > > -- > > > Martin Davis > > > Senior Technical Architect > > > Refractions Research, Inc. > > > (250) 383-3022 > > > > > > > > > > > > > ------------------------------------------------------------------------------ > > > Crystal Reports - New Free Runtime and 30 Day Trial > > > Check out the new simplified licensign option that enables > > unlimited > > > royalty-free distribution of the report engine for > > externally > > > facing > > > server and web deployment. > > > http://p.sf.net/sfu/businessobjects > > > _______________________________________________ > > > Jump-pilot-devel mailing list > > > Jump-pilot-devel@lists.sourceforge.net > <mailto:Jump-pilot-devel@lists.sourceforge.net> > > <mailto:Jump-pilot-devel@lists.sourceforge.net > <mailto:Jump-pilot-devel@lists.sourceforge.net>> > > > <mailto:Jump-pilot-devel@lists.sourceforge.net > <mailto:Jump-pilot-devel@lists.sourceforge.net> > > <mailto:Jump-pilot-devel@lists.sourceforge.net > <mailto:Jump-pilot-devel@lists.sourceforge.net>>> > > > > https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel > > > > > > > > > > > > > > > -- > > > http://amusingprogrammer.blogspot.com/ > > > > > > ------------------------------------------------------------------------ > > > > > > > > > > ------------------------------------------------------------------------------ > > > Crystal Reports - New Free Runtime and 30 Day Trial > > > Check out the new simplified licensign option that enables > unlimited > > > royalty-free distribution of the report engine for > > externally facing > > > server and web deployment. > > > http://p.sf.net/sfu/businessobjects > > > > > > ------------------------------------------------------------------------ > > > > > > _______________________________________________ > > > Jump-pilot-devel mailing list > > > Jump-pilot-devel@lists.sourceforge.net > <mailto:Jump-pilot-devel@lists.sourceforge.net> > > <mailto:Jump-pilot-devel@lists.sourceforge.net > <mailto:Jump-pilot-devel@lists.sourceforge.net>> > > > https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel > > > > > > > -- > > Martin Davis > > Senior Technical Architect > > Refractions Research, Inc. > > (250) 383-3022 > > > > > > > > ------------------------------------------------------------------------------ > > Crystal Reports - New Free Runtime and 30 Day Trial > > Check out the new simplified licensign option that enables > unlimited > > royalty-free distribution of the report engine for > externally > > facing > > server and web deployment. > > http://p.sf.net/sfu/businessobjects > > _______________________________________________ > > Jump-pilot-devel mailing list > > Jump-pilot-devel@lists.sourceforge.net > <mailto:Jump-pilot-devel@lists.sourceforge.net> > > <mailto:Jump-pilot-devel@lists.sourceforge.net > <mailto:Jump-pilot-devel@lists.sourceforge.net>> > > https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel > > > > > > > > > > -- > > http://amusingprogrammer.blogspot.com/ > > > ------------------------------------------------------------------------ > > > > > > ------------------------------------------------------------------------------ > > Crystal Reports - New Free Runtime and 30 Day Trial > > Check out the new simplified licensign option that enables unlimited > > royalty-free distribution of the report engine for > externally facing > > server and web deployment. > > http://p.sf.net/sfu/businessobjects > > > ------------------------------------------------------------------------ > > > > _______________________________________________ > > Jump-pilot-devel mailing list > > Jump-pilot-devel@lists.sourceforge.net > <mailto:Jump-pilot-devel@lists.sourceforge.net> > > https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel > > > > -- > Martin Davis > Senior Technical Architect > Refractions Research, Inc. > (250) 383-3022 > > > > ------------------------------------------------------------------------------ > Crystal Reports - New Free Runtime and 30 Day Trial > Check out the new simplified licensign option that enables unlimited > royalty-free distribution of the report engine for externally > facing > server and web deployment. > http://p.sf.net/sfu/businessobjects > _______________________________________________ > Jump-pilot-devel mailing list > Jump-pilot-devel@lists.sourceforge.net > <mailto:Jump-pilot-devel@lists.sourceforge.net> > https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel > > > > > -- > http://amusingprogrammer.blogspot.com/ > ------------------------------------------------------------------------ > > ------------------------------------------------------------------------------ > Crystal Reports - New Free Runtime and 30 Day Trial > Check out the new simplified licensign option that enables unlimited > royalty-free distribution of the report engine for externally facing > server and web deployment. > http://p.sf.net/sfu/businessobjects > ------------------------------------------------------------------------ > > _______________________________________________ > Jump-pilot-devel mailing list > Jump-pilot-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel > -- Martin Davis Senior Technical Architect Refractions Research, Inc. (250) 383-3022 ------------------------------------------------------------------------------ Crystal Reports - New Free Runtime and 30 Day Trial Check out the new simplified licensign option that enables unlimited royalty-free distribution of the report engine for externally facing server and web deployment. http://p.sf.net/sfu/businessobjects _______________________________________________ Jump-pilot-devel mailing list Jump-pilot-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel
