Merging database log files through log transformations

摘要

A method to construct a global equivalent database log file that transforms local log files from a parallel or distributed database system by extracting from each log file sequences of log entries from each database record, breaking the sequences into a series of segments, discarding the bulk of the segments and shortening other segments, then merging the remaining segments into an equivalent log file. The sequences are called "UID-sequences" and the segments "UID-segments" because they relate to one unique record ID or UID. The method also employs backward and forward superposition to further shorten the segments. This method works on database systems with or without instant constraint checks and also provides for treating log entries from multiple adjacent transactions on a log file as a single transaction. In systems with instant constraint checks, this method performs a "unique-key check" and a "foreign-key check" and resolves conflicts that are created because of superposition.