= !MapGuide RFC 114 - Extend MapGuide Transaction API to Support Save Points =

This page contains a change request (RFC) for the !MapGuide Open Source project.
More !MapGuide RFCs can be found on the [wiki:MapGuideRfcs RFCs] page.


== Status ==

||RFC Template Version||(1.0)||
||Submission Date||June 10, 2011||
||Last Modified||Sam Wang, June 10, 2011||
||Author||Sam Wang||
||RFC Status||Not ready for review||
||Implementation Status||Not started||
||Proposed Milestone||2.3||
||Assigned PSC guide(s)||Bruce Dechant||
||'''Voting History'''||(vote date)||
||+1|| ||
||+0|| ||
||-0|| ||
||-1|| ||
||no vote|| ||

== Overview ==

This RFC proposes a solution to extend MapGuide transaction API to support save points.  

== Motivation ==
Due to the constraint of FDO transaction, MapGuide does not support save or nested transaction. Thus it is impossible to partially rollback the work of a transaction. Now with FDO RFC 61(http://trac.osgeo.org/fdo/wiki/FDORfc61) adopted, we can take advantage of these new APIs and enhance MapGuide feature transaction API to control the commit or rollback of a transaction at a lower level.

== Proposed Solution ==
The current "!MgTransaction" interface can add the following methods to support save points which keeps consistency with FDO transaction API.

{{{
/////////////////////////////////////////////////////////////////
/// \brief
/// MgTransaction represents a transaction to be performed in a DataStore.
/// If the transaction is time out, commit or rollback a transaction will
/// result in one exception MgFeatureServiceException thrown.
class MG_PLATFORMBASE_API MgTransaction : public MgSerializable
{
PUBLISHED_API:
......

    /// \brief
    ///  Create a save point in this transaction.
    /// 
    /// \param suggestName
    /// Suggested save point name.
    /// 
    /// \returns 
    /// The actual name used
    virtual FdoString* AddSavePoint(FdoString* suggestName) = 0;

    /// \brief
    ///  Release a specific save point.
    /// 
    /// \param savePointName 
    /// Save point name.
    /// 
    /// \returns 
    /// Returns nothing
 
    virtual void ReleaseSavePoint(FdoString* savePointName) = 0;
    
    /// \brief
    ///  Rollback the transaction to a specified save point.
    /// 
    /// \param savePointName 
    /// Save point name.
    /// 
    /// \returns 
    /// Returns nothing 
    virtual void Rollback(FdoString* savePointName) = 0;
......
}
}}}

Typically, the implementation of these API methods would forward the call request and parameters to corresponding FDO API.

== Implications ==
Existing C#, Java and PHP API would be updated to reflect this change. 


== Test Plan ==
Existing MapGuide existing feature service unit tests will be expanded to test the proposed enhancements defined above.

== Funding / Resources ==

Autodesk to provide funding/resources