debug_logical_replication_streaming Developer Parameter

The allowed values are buffered and immediate. The default is buffered. This parameter is intended to be used to test logical decoding and replication of large transactions. The effect of debug_logical_replication_streaming is different for the publisher and subscriber:

On the publisher side, debug_logical_replication_streaming allows streaming or serializing changes immediately in logical decoding. When set to immediate, stream each change if the streaming option of CREATE SUBSCRIPTION is enabled, otherwise, serialize each change. When set to buffered, the decoding will stream or serialize changes when logical_decoding_work_mem is reached.

On the subscriber side, if the streaming option is set to parallel, debug_logical_replication_streaming can be used to direct the leader apply worker to send changes to the shared memory queue or to serialize all changes to the file. When set to buffered, the leader sends changes to parallel apply workers via a shared memory queue. When set to immediate, the leader serializes all changes to files and notifies the parallel apply workers to read and apply them at the end of the transaction.