I'm playing around with tablespace (postgresq 9.4) and I found out what I believe is a bug in pg_tables. Basically if you create a database in a table space X and then you create a table on the database the table is created correctly on the tablespace X ( I did a check on the filesystem) however if you do a select on pg_tables the column tablespace for that table is empty and even worst if you dump the DB there is no reporting about the the database or table being on that tablespace. Even \d doesn't report that the table is in the tablespace X.
