Make column-level collation quoting dialect-specific

Fixed regression in 1.2 where newly repaired quoting
of collation names in :ticket:`3785` breaks SQL Server,
which explicitly does not understand a quoted collation
name.   Whether or not mixed-case collation names are
quoted or not is now deferred down to a dialect-level
decision so that each dialect can prepare these identifiers
directly.

Change-Id: Iaf0a8123d9bf4711219e320896bb28c5d2649304
Fixes: #4154

1 files changed, 8 insertions, 1 deletions

diff --git a/lib/sqlalchemy/sql/elements.py b/lib/sqlalchemy/sql/elements.py
index 2cc1d9c42..fd2c9c0bd 100644
--- a/lib/sqlalchemy/sql/elements.py
+++ b/lib/sqlalchemy/sql/elements.py
@@ -52,7 +52,7 @@ def collate(expression, collation):
     expr = _literal_as_binds(expression)
     return BinaryExpression(
         expr,
-        ColumnClause(collation),
+        CollationClause(collation),
         operators.collate, type_=expr.type)
 
 
@@ -3873,6 +3873,13 @@ class ColumnClause(Immutable, ColumnElement):
         return c
 
 
+class CollationClause(ColumnElement):
+    __visit_name__ = "collation"
+
+    def __init__(self, collation):
+        self.collation = collation
+
+
 class _IdentifiedClause(Executable, ClauseElement):
 
     __visit_name__ = 'identified'