Sequences are the primary reason we recommend using pglogical for major PostgreSQL version upgrades. Though they're often associated with tables, sequences are separate objects that only contain information about themselves. They're often overlooked because there are no events to capture regarding logical replication; there are no inserts, updates, or deletes to encode or decode.
Since pglogical is an extension and doesn't rely entirely upon logical decoding in order to operate, it also adds functionality to augment PostgreSQL. pglogical handles sequences by periodically refreshing the values on the subscriber system to ensure they're much higher than the last value on the provider. In the case of an upgrade, there should be no sequence conflict after switching to the new cluster.
This recipe will explain how to register sequences with pglogical...
