Gluesync for PostgreSQL

Logical decoding is the process of extracting all persistent changes to a database’s tables into a coherent, easy-to-understand format that can be interpreted without detailed knowledge of the database’s internal state. In PostgreSQL, logical decoding is implemented by decoding the contents of the write-ahead log, which describes changes on a storage level, into an application-specific form such as a stream of tuples or SQL statements. In the context of logical replication, a slot represents a stream of changes that can be replayed to a client in the order they were made on the origin server. Each slot streams a sequence of changes from a single database.

A trigger is a specification that the database should automatically execute a particular function whenever a certain type of operation is performed. Triggers can be defined to execute either before or after any INSERT, UPDATE, or DELETE operation, either once per modified row, or once per SQL statement. If a trigger event occurs, the trigger’s function is called at the appropriate time to handle the event. PostgreSQL offers both per-row triggers and per-statement triggers. With a per-row trigger, the trigger function is invoked once for each row that is affected by the statement that fired the trigger. Gluesync’s GDC (Gluesync Data Capture) feature is based on a mix of per-row & per-statement triggers, more specifically Gluesync adopts an optimized triggers structure to catch events generated by operations that hit fields in your source PostgreSQL database.