I'm not sure I understand what you're doing. Nearly all DDL is written to the WAL segments. The only ones that aren't are things like unlogged and temporary tables. I don't think temporary tables used by queries are written either. Why do you think, however, that this isn't captured? --
We have an use case to copy the data from Salesforce to PostgreSQL environment but because of DDL changes that can happen to tables from Salesforce application side, replication would eventually fail. Do we have any open source tools that can also capture the DDL changes and replicate to PostgreSQL?
