Fix #16: Ensure that irr data doesn't lose datetime precision

Signed-off-by: Andrew MacDonald <andrew@maccas.net>

phildb/writer.py

@@ -238,6 +238,9 @@ def write_irregular_data(tsdb_file, series):
     """
     existing = __read(tsdb_file)
 
+    if series.dtype == np.float32:
+        series = series.astype(np.float64)
+
     overlap_idx = existing.index.intersection(series.index)
     modified = series.ix[overlap_idx] != existing.value.ix[overlap_idx]
     records_to_modify = existing.loc[overlap_idx].ix[modified.values]

tests/test_writer.py

@@ -548,3 +548,28 @@ def test_empty_series_write(self):
         log_entries = writer.write(self.tsdb_existing_file, pd.Series([]), 'D')
         self.assertEqual(0, len(log_entries['C']))
         self.assertEqual(0, len(log_entries['U']))
+
+    def test_float32_irregular_write(self):
+        """
+            Test irregular write of float32 data.
+
+            See: https://github.com/amacd31/phildb/issues/16
+        """
+
+        sample = pd.Series(
+            pd.np.array(
+                [x + 0.1 for x in range(10)],
+                dtype=pd.np.float32
+            ),
+            index=pd.date_range(
+                '2017-08-06 06:50:00+00:00',
+                periods=10,
+                freq='1T'
+            )
+        )
+
+        log_entries = writer.write(self.tsdb_existing_file, sample, 'IRR')
+        data = reader.read(self.tsdb_existing_file)
+
+        self.assertEqual(datetime(2017,8,6,6,50,0,0), data.index[0].to_pydatetime())
+        self.assertEqual(datetime(2017,8,6,6,51,0,0), data.index[1].to_pydatetime())