Changes between Version 3 and Version 4 of MapGuideRfc46

Timestamp:

Mar 14, 2008, 3:38:57 PM (16 years ago)

Author:

ronnielouie

Comment:

--

MapGuideRfc46

@@ -27 +27 @@
 == Motivation ==
 
-The current MgSelectionBase::GenerateFilter() API returns a string representing a filter for a set of selected features.  This filter string would look something like: "FeatId = 1109 OR FeatId = 1130 OR FeatId = 2065" such that each of the IDs of the selected features is explicitly specified.  The string is then passed as the filter to MgFeatureService::SelectFeatures() to query the datastore.   
+The current MgSelectionBase::GenerateFilter() API returns a string representing a filter for a set of selected features.  
+
+{{{
+ STRING MgSelectionBase::GenerateFilter(MgLayerBase* layer, CREFSTRING className);
+}}}
+
+This filter string would look something like: "FeatId = 1109 OR FeatId = 1130 OR FeatId = 2065" such that each of the IDs of the selected features is explicitly specified.  The string is then passed as the filter to MgFeatureService::SelectFeatures() to query the datastore.   
 
 A selection can contain an unlimited number of features, which means that the filter will contain an unlimited number of OR conditions.  However, most datastores have a finite number of OR's that can be supported, and some data sources, such as Access databases, are limited to a relatively small number or OR conditions.  
 
-Results can be unpredictable when the limit is exceeded due to buffer overruns and/or memory corruption leading to instability in the MapGuide Server.  In an effort to improve stability, GenerateFilter() was modified to return a string representing a smaller subset of the total selected features.
+Results can be unpredictable when the limit is exceeded due to buffer overruns and/or memory corruption leading to instability in the MapGuide Server.  In an effort to improve stability, GenerateFilter() was modified to return a string representing a smaller, but incomplete subset of the total selected features.
 
 == Proposed Solution ==
 
-This is a more detailed description of the actual changes desired.  The contents of this section will vary based on the target of the RFC, be it a technical change, website change, or process change.  For example, for a technical change, items such as files, XML schema changes, and API chances would be identified.  For a process change, the new process would be laid out in detail.  For a website change, the files affected would be listed.
+Exposing a new API to return a collection of smaller filters for a set of selected features will allow for querying of the datastore without compromising Server stability.
+
+Proposed New API: 
+
+{{{
+ MgStringCollection* MgSelectionBase::GenerateFilters(MgLayerBase* layer, CREFSTRING className, INT32 selectionSize);
+}}}
+
+The selectionSize parameter specifies the maximum size for each of the individual filters in the collection.  For example, if selectionSize = 20, the maximum number of features represented by an individual filter is 20.  The collection could contain an unlimited number of filters to handle an unlimited number of features.
 
 == Implications ==
 
-This section allows discussion of the repercussions of the change, such as whether there will be any breakage in backwards compatibility, if documentation will need to be updated, etc.
+Code that currently calls MgSelectionBase::GenerateFilter() should be updated to use MgSelectionBase::GenerateFilters() instead, and the caller will be required to process all the filters in the collection to correctly query the complete selection set.  In places where a relatively small number of features are expected in a selection (i.e. less than the value specified by SelectionFilterSize in serverconfig.ini/webconfig.ini), MgSelectionBase::GenerateFilter() can still be safely used to return correct results.
+
+This is a new API which will need to be documented.
 
 == Test Plan ==
 
-How the proposed change will be tested, if applicable.  New unit tests should be detailed here???
+Test existing APIs to ensure functionality does not change. Test NEW APIs functionality.
 
 == Funding/Resources ==
 
-This section will confirm that the proposed feature has enough support to proceed.  This would typically mean that the entity making the changes would put forward the RFC, but a non-developer could act as an RFC author if they are sure they have the funding to cover the change.
+Autodesk to supply