mhm.. although I must admit that I understand only half of what you all write - I like the idea of MutableBasicFeature (BMF).
However, this would also require to check which (analysis and editing) tools use BasicFeature by now - so that a MBF would be created again. On the other hand, if they are created - would not need a MBF feature because they are new anyway... (so maybe I am wrong with this thought anyway) with respect to changing geometries - not sure, could be that I have done this in algorithms of my generalization toolbox (using for instance coordinate filter - or is the use of that save?). stefan Martin Davis 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/ >> > > > >> > > >> > >> ------------------------------------------------------------------------ >> > > > >> > > > >> > > >> > >> >> ------------------------------------------------------------------------------ >> > > > >> > > > >> > > >> > >> ------------------------------------------------------------------------ >> > > > >> > > > _______________________________________________ >> > > > 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
