[autotest] Add a model for the hqe index table.

Added a model to afe/models.py for the new table
host_queue_entry_start_time_index.

BUG=chromium:704997
TEST=None

Change-Id: Ie3f320d27e48dd0612eeff35b6dc79828010c95f
Reviewed-on: https://chromium-review.googlesource.com/508471
Commit-Ready: Paul Hobbs <phobbs@google.com>
Tested-by: Paul Hobbs <phobbs@google.com>
Reviewed-by: Aviv Keshet <akeshet@chromium.org>
diff --git a/frontend/afe/models.py b/frontend/afe/models.py
index ac5d3ba..fc63c35 100644
--- a/frontend/afe/models.py
+++ b/frontend/afe/models.py
@@ -1832,6 +1832,16 @@
         return u"%s/%d (%d)" % (hostname, self.job.id, self.id)
 
 
+class HostQueueEntryStartTimes(dbmodels.Model):
+    """An auxilary table to HostQueueEntry to index by start time."""
+    insert_time = dbmodels.DateField()
+    highest_hqe_id = dbmodels.IntegerField()
+
+    class Meta:
+        """Metadata for class HostQueueEntryStartTimes."""
+        db_table = 'host_queue_entry_start_times'
+
+
 class AbortedHostQueueEntry(dbmodels.Model, model_logic.ModelExtensions):
     """Represents an aborted host queue entry."""
     queue_entry = dbmodels.OneToOneField(HostQueueEntry, primary_key=True)