When testing \watch, I noticed that process waits indefinitely when executing it with a DDL or a DML. For example: postgres=# CREATE TABLE aa (a int); postgres=# ANALYSE aa \watch 10
-- Process waiting here
By referring at do_watch:command.c, the feature is made such as there is no error if command returns no tuples:
default: /* should we fail for non-tuple-result commands? */ break;
The user can interrupt the process if wanted, but shouldn't it make more sense to return directly an error to the user instead of making the process wait indefinitely?