Every time I run postgres instance, I need to manually set the search_path to be to ag_catalog by SET search_path=ag_catalog; and then load the age, is there a way makes me don't need to every time to do that?
The default schema/search_path is 'public'. In order to change the default search_path to 'ag_catalog' instead of public, you need to make a change to the postgresql.conf file inside your db cluster folder. You need to uncomment and change the search_path as
search_path = 'ag_catalog, "$user", public' # schema names