Query related to Logical Replication using test_decoding and unchanged-toast-datum

[Kiran K V <kirankv.1982@xxxxxxxxx>]

Hi,

I am currently using PostgreSQL version 16 and the test_decoding plugin to perform logical replication (using replication slots). I have a simple table with integer column and JSON column. When a non-JSON column is updated, the value "unchanged-toast-datum" for the JSON column is obtained. This shows that the value recorded in a TOAST table for a JSON column value has not changed and is as expected. could you please tell me whether PostgreSQL will truly log these values to WAL or not ? If not, what will be entered into WAL for the JSON column if it remains unchanged?

Please let me know. Thank you very much.

Regards,

Kiran