BUG: Fixed bugs in join_by and added tests

1 files changed, 10 insertions, 3 deletions

diff --git a/numpy/lib/recfunctions.py b/numpy/lib/recfunctions.py
index b3c210fff..0127df9f9 100644
--- a/numpy/lib/recfunctions.py
+++ b/numpy/lib/recfunctions.py
@@ -895,6 +895,13 @@ def join_by(key, r1, r2, jointype='inner', r1postfix='1', r2postfix='2',
     (nb1, nb2) = (len(r1), len(r2))
     (r1names, r2names) = (r1.dtype.names, r2.dtype.names)
 
+    # Check the names for collision
+    if (set.intersection(set(r1names),set(r2names)).difference(key) and
+            not (r1postfix or r2postfix)):
+        msg = "r1 and r2 contain common names, r1postfix and r2postfix "
+        msg += "can't be empty"
+        raise ValueError(msg)
+
     # Make temporary arrays of just the keys
     r1k = drop_fields(r1, [n for n in r1names if n not in key])
     r2k = drop_fields(r2, [n for n in r2names if n not in key])
@@ -937,7 +944,7 @@ def join_by(key, r1, r2, jointype='inner', r1postfix='1', r2postfix='2',
         name = desc[0]
         # Have we seen the current name already ?
         if name in names:
-            nameidx = names.index(name)
+            nameidx = ndtype.index(desc)
             current = ndtype[nameidx]
             # The current field is part of the key: take the largest dtype
             if name in key:
@@ -960,7 +967,7 @@ def join_by(key, r1, r2, jointype='inner', r1postfix='1', r2postfix='2',
     names = output.dtype.names
     for f in r1names:
         selected = s1[f]
-        if f not in names:
+        if f not in names or (f in r2names and not r2postfix and not f in key):
             f += r1postfix
         current = output[f]
         current[:r1cmn] = selected[:r1cmn]
@@ -968,7 +975,7 @@ def join_by(key, r1, r2, jointype='inner', r1postfix='1', r2postfix='2',
             current[cmn:cmn + r1spc] = selected[r1cmn:]
     for f in r2names:
         selected = s2[f]
-        if f not in names:
+        if f not in names or (f in r1names and not r1postfix and f not in key):
             f += r2postfix
         current = output[f]
         current[:r2cmn] = selected[:r2cmn]