Firedac option MergeDataMode incomprehensibility

[Jacek Laskowski 57]

I read help topis about MergeDataMode options in Firedac datasets:

 

http://docwiki.embarcadero.com/Libraries/Tokyo/en/FireDAC.Stan.Intf.TFDMergeDataMode

 

How is difference between dmDeltaMerge and dmDataMerge?

[f.m 8]

TFDMergeDataMode.dmDeltaMerge mantains source record UpdateStatus:

Source Record UpdateStatus   Primary key exists ?    Dest Record UpdateStatus
  usInserted                   No                      usInserted
  usInserted                   Yes                     usModified

After MergeDataSet(dmDeltaMerge), UpdatesPending is true, so it is possible to use ApplyUpdates().

 

 

TFDMergeDataMode.dmDataMerge changes UpdateStatus to usUnmodified:

  Source Record UpdateStatus   Primary key exists ?    Dest Record UpdateStatus
  usInserted                   No                      usUnmodified
  usInserted                   Yes                     usUnmodified

After MergeDataSet(dmDataMerge), UpdatesPending is false.