Incrementally sychronizing occasionally-connected mobile databases, preserving horizontal filter scope consistency by using client pre-image

摘要

A system for synchronizing data on a first device with data at a second device, includes: determining a pre-image of the data on the first device according to a filter after a previous synchronization with the data at the second device; determining a current image of the data at the second device according to the filter; determining a delta of the current image, where the delta comprises data that exists in the current image and has changed since the previous synchronization; instructing the first device to delete data that exists in the pre-image but not in the current image; and instructing the first device to UPSERT a union of the data that exists in the delta and the data that exists in the current image but not the pre-image. This is efficient in time and bandwidth resources while also providing consistent data integrity.