SQLStore and data diffs

This article contains some preliminary notes about how the filter data diffs after a completed update.

By the time the  hook is triggered, the storage update of the   has been completed. To help succeeding processes to operate on information that were available before and after the update, CiteRef::gh:smw:1108 contains the raw input of that update operation.

A more convenient interface to pass through the data diffs is provided with the 's CiteRef::gh:smw:1648.