CREATE EXTENSION BLOCKS

Hackers,

I am working on scripts to copy data from Oracle via oracle_fdw. They each do something like this:
   CREATE SCHEMA migrate_stuff;   SET search_path TO migrate_stuff,public;   CREATE EXTENSION oracle_fdw SCHEMA
migrate_rules;
   CREATE SERVER oracle_stuff FOREIGN DATA WRAPPER oracle_fdw   OPTIONS (dbserver :'oracle_uri');
   CREATE USER MAPPING FOR postgres SERVER oracle_stuff   OPTIONS (user :'oracle_user', password :'oracle_pass');
   CREATE FOREIGN TABLE migrate_stuff (      stuff_id integer,      name     text   ) SERVER oracle_rules OPTIONS(table
'STUFF');     INSERT INTO my.stuff SELECT * FROM migrate_stuff; 
   DROP SCHEMA migrate_stuff CASCADE;   COMMIT;

Then I run them in parallel:
   for file in migrate*.sql; do       psql -d foo -f $file &   done   wait

This works fine except for one thing: the first CREATE EXTENSION statement blocks all the others. Even when I create
theextension in separate schemas in each script! I have to remove the CREATE EXTENSION statement, create it in public
beforeany of the scripts run, then drop it when they're done. I'm okay with this workaround, but wasn't sure if the
blockingof CREATE EXTENSION was intentional or a known issue (id did not see it documented in
http://www.postgresql.org/docs/current/static/sql-createextension.html).

Thanks,

David