diff --git a/lib/ansible/modules/database/postgresql/postgresql_info.py b/lib/ansible/modules/database/postgresql/postgresql_info.py
index f08b3ab644..f9e1763674 100644
--- a/lib/ansible/modules/database/postgresql/postgresql_info.py
+++ b/lib/ansible/modules/database/postgresql/postgresql_info.py
@@ -486,36 +486,33 @@ from ansible.module_utils.six import iteritems
 #
 
 class PgDbConn(object):
+
+    """Auxiliary class for working with PostgreSQL connection objects.
+
+    Arguments:
+        module (AnsibleModule): Object of AnsibleModule class that
+            contains connection parameters.
+    """
+
     def __init__(self, module):
         self.module = module
         self.db_conn = None
         self.cursor = None
-        self.session_role = self.module.params.get('session_role')
 
     def connect(self):
-        try:
-            self.db_conn = connect_to_db(self.module, warn_db_default=False)
-            self.cursor = self.db_conn.cursor(cursor_factory=DictCursor)
+        """Connect to a PostgreSQL database and return a cursor object.
 
-            # Switch role, if specified:
-            if self.session_role:
-                try:
-                    self.cursor.execute('SET ROLE %s' % self.session_role)
-                except Exception as e:
-                    self.module.fail_json(msg="Could not switch role: %s" % to_native(e))
-
-            return self.cursor
-
-        except TypeError as e:
-            if 'sslrootcert' in e.args[0]:
-                self.module.fail_json(msg='PostgreSQL server must be at least version 8.4 '
-                                          'to support sslrootcert')
-            self.module.fail_json(msg="Unable to connect to database: %s" % to_native(e))
-
-        except Exception as e:
-            self.module.fail_json(msg="Unable to connect to database: %s" % to_native(e))
+        Note: connection parameters are passed by self.module object.
+        """
+        self.db_conn = connect_to_db(self.module, warn_db_default=False)
+        return self.db_conn.cursor(cursor_factory=DictCursor)
 
     def reconnect(self, dbname):
+        """Reconnect to another database and return a PostgreSQL cursor object.
+
+        Arguments:
+            dbname (string): Database name to connect to.
+        """
         self.db_conn.close()
 
         self.module.params['database'] = dbname
@@ -523,6 +520,14 @@ class PgDbConn(object):
 
 
 class PgClusterInfo(object):
+
+    """Class for collection information about a PostgreSQL instance.
+
+    Arguments:
+        module (AnsibleModule): Object of AnsibleModule class.
+        db_conn_obj (psycopg2.connect): PostgreSQL connection object.
+    """
+
     def __init__(self, module, db_conn_obj):
         self.module = module
         self.db_obj = db_conn_obj
@@ -539,6 +544,9 @@ class PgClusterInfo(object):
         }
 
     def collect(self, val_list=False):
+        """
+        Collect information based on 'filter' option.
+        """
         subset_map = {
             "version": self.get_pg_version,
             "tablespaces": self.get_tablespaces,
@@ -850,6 +858,9 @@ class PgClusterInfo(object):
         return nsp_dict
 
     def get_pg_version(self):
+        """
+        Get major and minor PostgreSQL server version.
+        """
         query = "SELECT version()"
         raw = self.__exec_sql(query)[0][0]
         raw = raw.split()[1].split('.')
@@ -859,6 +870,10 @@ class PgClusterInfo(object):
         )
 
     def get_db_info(self):
+        """
+        Get information about the current database.
+        """
+
         # Following query returns:
         # Name, Owner, Encoding, Collate, Ctype, Access Priv, Size
         query = ("SELECT d.datname, "
@@ -897,9 +912,15 @@ class PgClusterInfo(object):
         self.pg_info["databases"] = db_dict
 
     def __get_pretty_val(self, setting):
+        """
+        Get setting's value represented by SHOW command.
+        """
         return self.__exec_sql("SHOW %s" % setting)[0][0]
 
     def __exec_sql(self, query):
+        """
+        Execute SQL and return the result.
+        """
         try:
             self.cursor.execute(query)
             res = self.cursor.fetchall()