All three commands are captured by the event trigger. The first and second command ends up getting deparsed, WAL-logged and replayed on the subscriber. The replay of the ALTER TABLE command causes a duplicate constraint error. The problem is that while subcommands are captured by event triggers by default, they don't need to be deparsed and WAL-logged for DDL replication. To do that we can pass the isCompleteQuery variable in ProcessUtilitySlow to EventTriggerCollectSimpleCommand() and EventTriggerAlterTableEnd() and make this information available in CollectedCommand so that any subcommands can be skipped.
May not be able to skip any subcommands.
like ' ALTER TABLE ctlt1_like ALTER COLUMN b SET STORAGE EXTERNAL;'
It cannot be represented in the CREATE TABLEstatement.
