Fix issue 216 (pandas-dev#321)

Addresses issue 216 by allowing index column to be named in tickstore

CHANGES.md

@@ -4,6 +4,7 @@
   * Bugfix:  #300 to_datetime deprecated in pandas, use to_pydatetime instead
   * Bugfix:  #309 formatting change for DateRange ```__str__```
   * Feature: #313 set and read user specified metadata in chunkstore
+  * Bugfix:  #216 Tickstore write fails with named index column
 
 ### 1.36 (2016-12-13)
 

arctic/tickstore/tickstore.py

@@ -509,7 +509,8 @@ def write(self, symbol, data, initial_image=None):
         data : list of dicts or a pandas.DataFrame
             List of ticks to store to the tick-store.
             if a list of dicts, each dict must contain a 'index' datetime
-            if a pandas.DataFrame the index must be a Timestamp that can be converted to a datetime
+            if a pandas.DataFrame the index must be a Timestamp that can be converted to a datetime.
+            Index names will not be preserved.
         initial_image : dict
             Dict of the initial image at the start of the document. If this contains a 'index' entry it is
             assumed to be the time of the timestamp of the index
@@ -628,6 +629,7 @@ def _pandas_to_bucket(df, symbol, initial_image):
         logger.warning("NB treating all values as 'exists' - no longer sparse")
         rowmask = Binary(lz4.compressHC(np.packbits(np.ones(len(df), dtype='uint8'))))
 
+        index_name = df.index.names[0] or "index"
         recs = df.to_records(convert_datetime64=False)
         for col in df:
             array = TickStore._ensure_supported_dtypes(recs[col])
@@ -636,9 +638,8 @@ def _pandas_to_bucket(df, symbol, initial_image):
             col_data[ROWMASK] = rowmask
             col_data[DTYPE] = TickStore._str_dtype(array.dtype)
             rtn[COLUMNS][col] = col_data
-        rtn[INDEX] = Binary(lz4.compressHC(np.concatenate(([recs['index'][0].astype('datetime64[ms]').view('uint64')],
-                                                           np.diff(recs['index'].astype('datetime64[ms]').view('uint64')))
-                                                          ).tostring()))
+        rtn[INDEX] = Binary(lz4.compressHC(np.concatenate(([recs[index_name][0].astype('datetime64[ms]').view('uint64')],
+                                                           np.diff(recs[index_name].astype('datetime64[ms]').view('uint64')))).tostring()))
         return rtn, final_image
 
     @staticmethod

tests/integration/tickstore/test_ts_write.py

@@ -79,3 +79,20 @@ def test_ts_write_pandas(tickstore_lib):
 
     read = tickstore_lib.read('SYM', columns=None)
     assert_frame_equal(read, data, check_names=False)
+
+
+def test_ts_write_named_col(tickstore_lib):
+    data = DUMMY_DATA
+    tickstore_lib.write('SYM', data)
+
+    data = tickstore_lib.read('SYM')
+    assert data.index[0] == dt(2013, 1, 1, tzinfo=mktz('Europe/London'))
+    assert data.a[0] == 1
+    assert(data.index.name is None)
+    data.index.name = 'IndexName'
+
+    tickstore_lib.delete('SYM')
+    tickstore_lib.write('SYM', data)
+
+    read = tickstore_lib.read('SYM')
+    assert(read.index.name is None)