wal2json is an output plugin for logical decoding. It means that the
plugin have access to tuples produced by INSERT and UPDATE. Also,
UPDATE/DELETE old row versions can be accessed depending on the
configured replica identity. Changes can be consumed using the streaming
protocol (logical replication slots) or by a special SQL API.
The wal2json output plugin produces a JSON object per transaction. All
of the new/old tuples are available in the JSON object. Also, there are
options to include properties such as transaction timestamp,
schema-qualified, data types, and transaction ids.