How ejabberd stores information in database

I built ejabberd with postgresql, and i wonders how ejabberd stores information in the database.
Because after I looked at the log for postgresql, I only saw insert and select statements on users table, all other tables are not populated even though I have added contacts.
I want to integrate my rails application with ejabberd database, can anyone explain the database tables for me?
Here's a list of the database tables.

ejabberd=# \d
List of relations
Schema | Name | Type | Owner
--------+--------------------------+----------+----------
public | last | table | postgres
public | privacy_default_list | table | postgres
public | privacy_list | table | postgres
public | privacy_list_data | table | postgres
public | privacy_list_id_seq | sequence | postgres
public | private_storage | table | postgres
public | pubsub_item | table | postgres
public | pubsub_node | table | postgres
public | pubsub_node_nodeid_seq | sequence | postgres
public | pubsub_node_option | table | postgres
public | pubsub_node_owner | table | postgres
public | pubsub_state | table | postgres
public | pubsub_state_stateid_seq | sequence | postgres
public | pubsub_subscription_opt | table | postgres
public | roster_version | table | postgres
public | rostergroups | table | postgres
public | rosterusers | table | postgres
public | spool | table | postgres
public | spool_seq_seq | sequence | postgres
public | users | table | postgres
public | vcard | table | postgres
public | vcard_search | table | postgres