Tool attempts to logically replicate system tables provided by extensions

[nickgsc]

After successfully setting up logical replication, we are encountering the following error over and over again in our target database:

[webapp-db-sbx-1]2020-11-10T23:21:01.098136[postgresql-12][85-1] user=,db=,app=,client= LOG: logical replication table synchronization worker for subscription "aiven_db_migrate_dafhp6nhpahgqn_sub", table "spatial_ref_sys" has started
[webapp-db-sbx-1]2020-11-10T23:21:01.145297[postgresql-12][86-1] user=,db=,app=,client= ERROR: duplicate key value violates unique constraint "spatial_ref_sys_pkey"
[webapp-db-sbx-1]2020-11-10T23:21:01.145522[postgresql-12][86-2] user=,db=,app=,client= DETAIL: Key (srid)=(3819) already exists.
[webapp-db-sbx-1]2020-11-10T23:21:01.145589[postgresql-12][86-3] user=,db=,app=,client= CONTEXT: COPY spatial_ref_sys, line 1
[webapp-db-sbx-1]2020-11-10T23:21:01.148562[postgresql-12][85-1] user=,db=,app=,client= LOG: background worker "logical replication worker" (PID 2368) exited with exit code 1

The table in question here, spatial_ref_sys, is one of the system tables from the postgis extension. The table is populated when the extension is created, so it makes sense that trying to logically replicate the contents of this table is failing because the data is already there.

Since it is not currently possible to specify include/exclude lists of tables, there is no way to avoid this from happening when postgis is one of the extensions that is replicated. I imagine the same issue exists for other extensions that have their own built-in/system tables as well.