While working on AEM Content Fragments we noticed that there is a new jcr property which is "fragmentlastsave" and trying to figure out the purpose of this property. The value getting stored is same as value stored as part of jcr:lastModifed date. Any can provide the justification for this?
I couldn't tell you exactly when jcr:lastModified might be used vs lastFragmentSave within AEM's internal logic.
What I can say is that lastFragmentSave is the a timestamp indicating the last time at which original fragment was saved, whereas jcr:lastModified is a more generic timestamp that indicates when the resource as a whole was last modified.
You can see the difference between these two concepts when you create a variation of a fragment:
The original fragment doesn't change so lastFragmentSave isn't updated.
However, the creation of a variation is an update of the resource, so jcr:lastModifiedis updated 🙂
In this screenshot you can see that, in this example, the two are about a minute a part.