>
> 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>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>> 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>>> 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>>>> 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/
> > > > >
> > > >
> > >
> >
> ------------------------------------------------------------------------
> > > > >
> > > > >
> > > >
> > >
> >
> ------------------------------------------------------------------------------
> > > > >
> > > > >
> > > >
> > >
> >
> ------------------------------------------------------------------------
> > > > >
> > > > > _______________________________________________
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> > <mailto:Jump-pilot-devel@lists.sourceforge.net>
> > > <mailto:Jump-pilot-devel@lists.sourceforge.net
> > <mailto:Jump-pilot-devel@lists.sourceforge.net>>
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> > <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
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> > <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
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> > > > royalty-free distribution of the report engine for
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> > > > server and web deployment.
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> > > >
> > >
> >
> ------------------------------------------------------------------------
> > > >
> > > > _______________________________________________
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> > > <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
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> > <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
> > >
> >
> ------------------------------------------------------------------------
> > >
> > > _______________________________________________
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> > <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
> _______________________________________________
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> https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel
>
--
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