merge r6418 from 0.5, dedupe expressions on clause ident, not string value

[ticket:1574]

1 files changed, 43 insertions, 0 deletions

diff --git a/test/sql/test_select.py b/test/sql/test_select.py
index 757dc5213..3dc09c9df 100644
--- a/test/sql/test_select.py
+++ b/test/sql/test_select.py
@@ -182,6 +182,49 @@ sq.myothertable_othername AS sq_myothertable_othername FROM (" + sqstring + ") A
             , dialect=default.DefaultDialect(paramstyle='pyformat')
         )
         
+    def test_dupe_columns(self):
+        """test that deduping is performed against clause element identity, not rendered result."""
+        
+        self.assert_compile(
+            select([column('a'), column('a'), column('a')]),
+            "SELECT a, a, a"
+            , dialect=default.DefaultDialect()
+        )
+
+        c = column('a')
+        self.assert_compile(
+            select([c, c, c]),
+            "SELECT a"
+            , dialect=default.DefaultDialect()
+        )
+
+        a, b = column('a'), column('b')
+        self.assert_compile(
+            select([a, b, b, b, a, a]),
+            "SELECT a, b"
+            , dialect=default.DefaultDialect()
+        )
+        
+        self.assert_compile(
+            select([bindparam('a'), bindparam('b'), bindparam('c')]),
+            "SELECT :a, :b, :c"
+            , dialect=default.DefaultDialect(paramstyle='named')
+        )
+
+        self.assert_compile(
+            select([bindparam('a'), bindparam('b'), bindparam('c')]),
+            "SELECT ?, ?, ?"
+            , dialect=default.DefaultDialect(paramstyle='qmark'),
+        )
+
+        self.assert_compile(
+            select(["a", "a", "a"]),
+            "SELECT a, a, a"
+        )
+        
+        s = select([bindparam('a'), bindparam('b'), bindparam('c')])
+        s = s.compile(dialect=default.DefaultDialect(paramstyle='qmark'))
+        eq_(s.positiontup, ['a', 'b', 'c'])
         
     def test_nested_uselabels(self):
         """test nested anonymous label generation.  this