BUG: Fix an issue in merging blocks where the resulting DataFrame had partially set _ref_locs

doc/source/release.rst

@@ -94,8 +94,10 @@ pandas 0.13
   - Fixed an issue where ``PeriodIndex`` joining with self was returning a new
     instance rather than the same instance (:issue:`4379`); also adds a test
     for this for the other index types
-  - Fixed a bug with all the dtypes being converted to object when using the CSV cparser 
+  - Fixed a bug with all the dtypes being converted to object when using the CSV cparser
     with the usecols parameter (:issue: `3192`)
+  - Fix an issue in merging blocks where the resulting DataFrame had partially
+    set _ref_locs (:issue:`4403`)
 
 pandas 0.12
 ===========

pandas/tests/test_frame.py

@@ -1,3 +1,5 @@
+# -*- coding: utf-8 -*-
+
 from __future__ import print_function
 # pylint: disable-msg=W0612,E1101
 from copy import deepcopy
@@ -2956,6 +2958,27 @@ def check(result, expected=None):
         expected = np.array([[1,2.5],[3,4.5]])
         self.assert_((result == expected).all().all())
 
+        # rename, GH 4403
+        df4 = DataFrame({'TClose': [22.02],
+                         'RT': [0.0454],
+                         'TExg': [0.0422]},
+                        index=MultiIndex.from_tuples([(600809, 20130331)], names=['STK_ID', 'RPT_Date']))
+
+        df5 = DataFrame({'STK_ID': [600809] * 3,
+                         'RPT_Date': [20120930,20121231,20130331],
+                         'STK_Name': [u('饡驦'), u('饡驦'), u('饡驦')],
+                         'TClose': [38.05, 41.66, 30.01]},
+                        index=MultiIndex.from_tuples([(600809, 20120930), (600809, 20121231),(600809,20130331)], names=['STK_ID', 'RPT_Date']))
+
+        k = pd.merge(df4,df5,how='inner',left_index=True,right_index=True)
+        result = k.rename(columns={'TClose_x':'TClose', 'TClose_y':'QT_Close'})
+        str(result)
+        result.dtypes
+
+        expected = DataFrame([[0.0454, 22.02, 0.0422, 20130331, 600809, u('饡驦'), 30.01 ]],
+                             columns=['RT','TClose','TExg','RPT_Date','STK_ID','STK_Name','QT_Close']).set_index(['STK_ID','RPT_Date'],drop=False)
+        assert_frame_equal(result,expected)
+
     def test_insert_benchmark(self):
         # from the vb_suite/frame_methods/frame_insert_columns
         N = 10

pandas/tools/merge.py

@@ -683,6 +683,7 @@ def get_result(self):
         blockmaps = self._prepare_blocks()
         kinds = _get_merge_block_kinds(blockmaps)
 
+        result_is_unique = self.result_axes[0].is_unique
         result_blocks = []
 
         # maybe want to enable flexible copying <-- what did I mean?
@@ -692,6 +693,12 @@ def get_result(self):
                 if klass in mapping:
                     klass_blocks.extend((unit, b) for b in mapping[klass])
             res_blk = self._get_merged_block(klass_blocks)
+
+            # if we have a unique result index, need to clear the _ref_locs
+            # a non-unique is set as we are creating
+            if result_is_unique:
+                res_blk.set_ref_locs(None)
+
             result_blocks.append(res_blk)
 
         return BlockManager(result_blocks, self.result_axes)
@@ -1070,7 +1077,7 @@ def _concat_blocks(self, blocks):
             # map the column location to the block location
             # GH3602
             if not self.new_axes[0].is_unique:
-                block._ref_locs = indexer
+                block.set_ref_locs(indexer)
 
             return block