Add Gerrit DB query method to gerritlib.

Sometimes you need to query the Gerrit DB directly instead of using the
Gerrit query abstraction layer. Add api method to communicate directly
to the DB.

Change-Id: I3ef3173cbe62741bb9d37f49abda1cf0eacbceff

gerritlib/gerrit.py

@@ -137,6 +137,22 @@ class Gerrit(object):
                 pprint.pformat(data)))
         return data
 
+    def dbQuery(self, query):
+        cmd = 'gerrit gsql --format JSON -c "%s"' % query
+        out, err = self._ssh(cmd)
+        if not out:
+            return False
+        lines = out.strip().split('\n')
+        if not lines:
+            return False
+        data = map(json.loads, lines)
+        if not data:
+            return False
+        self.log.debug("Received %s rows from Gerrit DB query: \n%s" % (
+                # Subtract one for query states line.
+                (len(data) - 1), query))
+        return data
+
     def _ssh(self, command):
         client = paramiko.SSHClient()
         client.load_system_host_keys()