Change table.get_timestamp to table.__getitem__

This lets us use simple indexing to get timestamps from the table,
which allows us to use 'bisect' directly without needing a proxy class.

nilmdb/server/bulkdata.py

@@ -478,7 +478,7 @@ class Table(object):
             row += count
         return "".join(ret)
 
-    def get_timestamp(self, row):
+    def __getitem__(self, row):
         """Extract timestamps from a row, with table[n] notation."""
         if (row is None or row < 0 or row >= self.nrows):
             raise IndexError("Index out of range")
@@ -575,11 +575,3 @@ class Table(object):
             self._remove_rows(subdir, filename, row_offset, row_offset + count)
             remaining -= count
             row += count
-
-class TimestampOnlyTable(object):
-    """Helper that lets us pass a Tables object into bisect, by
-    returning only the timestamp when a particular row is requested."""
-    def __init__(self, table):
-        self.table = table
-    def __getitem__(self, index):
-        return self.table.get_timestamp(index)

nilmdb/server/nilmdb.py

@@ -472,7 +472,7 @@ class NilmDB(object):
         # Optimization for the common case where an interval wasn't truncated
         if dbinterval.start == dbinterval.db_start:
             return dbinterval.db_startpos
-        return bisect.bisect_left(bulkdata.TimestampOnlyTable(table),
+        return bisect.bisect_left(table,
                                   dbinterval.start,
                                   dbinterval.db_startpos,
                                   dbinterval.db_endpos)
@@ -491,7 +491,7 @@ class NilmDB(object):
         # want to include the given timestamp in the results.  This is
         # so a queries like 1:00 -> 2:00 and 2:00 -> 3:00 return
         # non-overlapping data.
-        return bisect.bisect_left(bulkdata.TimestampOnlyTable(table),
+        return bisect.bisect_left(table,
                                   dbinterval.end,
                                   dbinterval.db_startpos,
                                   dbinterval.db_endpos)
@@ -539,7 +539,7 @@ class NilmDB(object):
             row_max = row_start + remaining
             if row_max < row_end:
                 row_end = row_max
-                restart = table.get_timestamp(row_max)
+                restart = table[row_max]
 
             # Gather these results up
             result.append(table.get_data(row_start, row_end))