Hi Michaël,
We need to track modifications on a per-feature basis because it is
> necessary to update a database source when a modification is done in the
> OJ UI : right/wrong
Right.
You propose to track modification on each attribute individually because
> you don't want to update a whole database record if a single attribute
> is changed : right/wrong
>
Wrong. Tracking individual attribute modification is necessary to determine
if the call to setAttribute is an initial load or a modification. No one
has yet demonstrated how a simpler (i.e. boolean flag) would be able to
track a modification. The pattern of use for Features is: create feature,
initialize feature, and later possibly modify feature. Initialization
involves multiple calls to setAttribute.
- I'm not sure why it is needed to differentiate first modification from
> other modifications
First modification is when you load the initial value (say from a
shapefile). This isn't modification as we need to define it.
> - why not a byte instead of a int to save memory usage if boolean is not
> sufficient ?
>
A byte would be sufficient. Actually we only need to count to two if java
has some kind of subrange integer capability?
Larry
2009/4/23 Michaël Michaud <michael.mich...@free.fr>
> Larry Becker a écrit :
> > 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...
> I have to admit I have not a clear idea about the goal and the proposal
> you made to track modifications. Please correct me if I am wrong :
> We need to track modifications on a per-feature basis because it is
> necessary to update a database source when a modification is done in the
> OJ UI : right/wrong
> You propose to track modification on each attribute individually because
> you don't want to update a whole database record if a single attribute
> is changed : right/wrong
> You proposed to use an int because you want to disntinguish at least
> three states for each attribute : empty, initialized, modified :
> right/wrong
>
> Notes :
> - I'm not sure why it is needed to differentiate first modification from
> other modifications
> - why not a byte instead of a int to save memory usage if boolean is not
> sufficient ?
> - in the proposed implementation, I do not see any chance to persist
> modification state of features (in case of disconnection for example) as
> the state is note stored in a standard feature attribute (but I'm also
> not sure persisting modification state makes sense).
>
> Michaël
> >
> > 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/
> > > > >
> > > >
> > >
> >
> ------------------------------------------------------------------------
> > > > >
> > > > >
> > > >
> > >
> >
> ------------------------------------------------------------------------------
> > > > >
> > > > >
> > > >
> > >
> >
> ------------------------------------------------------------------------
> > > > >
> > > > > _______________________________________________
> > > > > 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
> >
>
>
>
> ------------------------------------------------------------------------------
> 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
>
--
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
