Merge pull request #1216 from quantopian/relabel-fix

Relabel fix

blaze/compute/sql.py

@@ -686,6 +686,7 @@ def post_compute(t, s, **kwargs):
 
 @dispatch(ReLabel, Selectable)
 def compute_up(t, s, **kwargs):
+    s = s.alias()
     columns = [getattr(s.c, col).label(new_col)
                if col != new_col else
                getattr(s.c, col)

blaze/compute/tests/test_sql_compute.py

@@ -16,8 +16,8 @@
 
 from blaze.compute.sql import compute, select, lower_column, compute_up
 from blaze.expr import (
-    symbol, discover, transform, summary, by, sin, join,
-    floor, cos, merge, nunique, mean, sum, count, exp, concat,
+    symbol, transform, summary, by, sin, join,
+    floor, cos, merge, nunique, mean, sum, count, exp
 )
 from blaze.compatibility import xfail
 from blaze.utils import tmpfile, example
@@ -538,11 +538,35 @@ def test_label():
 
 def test_relabel():
     result = compute(t.relabel({'name': 'NAME', 'id': 'ID'}), s)
-    expected = select([s.c.name.label('NAME'), s.c.amount, s.c.id.label('ID')])
+    from_ = s.alias()
+    expected = select([
+        from_.c.name.label('NAME'),
+        from_.c.amount,
+        from_.c.id.label('ID'),
+    ])
 
     assert str(result) == str(expected)
 
 
+def test_relabel_selection():
+    result = compute(
+        t[['name', 'id']].relabel(name='new_name', id='new_id'),
+        s,
+    )
+    assert normalize(str(result)) == normalize(
+        """
+        select
+            anon_1.name as new_name,
+            anon_1.id as new_id
+        from
+            (select
+                 accounts.name as name,
+                 accounts.id as id
+             from accounts) as anon_1
+        """,
+    )
+
+
 def test_merge():
     col = (t['amount'] * 2).label('new')
 

docs/source/whatsnew/0.8.3.txt

@@ -69,3 +69,5 @@ Bug Fixes
   (:issue:`1207`)
 * Fixed a bug where the wrong value was being passed into
   :func:`~blaze.expr.datetime.time` (:issue:`1213`)
+* Fixed a bug in sql relabel that prevented relabeling anything that generated
+  a subselect. (:issue:`1216`)