Add _alembic_quote method to format_constraint()

Alembic needs a portable way of getting at the name of an
index without quoting being applied.   As we would like the
indexes created by the Column index=True flag to support
deferred index names, supply a function that delivers this
for Alembic without it having to dig too deeply into the
internals.    the _alembic_quote flag may be made public
at a later time, however as we've been through many quoting
flags that are difficult to get rid of, try to be conservative
to start.

Change-Id: I184adaeae26c2e75093aaea5ebe01a3815cadb08

1 files changed, 5 insertions, 2 deletions

diff --git a/lib/sqlalchemy/sql/compiler.py b/lib/sqlalchemy/sql/compiler.py
index 453ff56d2..c6c30629d 100644
--- a/lib/sqlalchemy/sql/compiler.py
+++ b/lib/sqlalchemy/sql/compiler.py
@@ -3698,7 +3698,7 @@ class IdentifierPreparer(object):
         return ident
 
     @util.dependencies("sqlalchemy.sql.naming")
-    def format_constraint(self, naming, constraint):
+    def format_constraint(self, naming, constraint, _alembic_quote=True):
         if isinstance(constraint.name, elements._defer_name):
             name = naming._constraint_name_for_table(
                 constraint, constraint.table
@@ -3725,7 +3725,10 @@ class IdentifierPreparer(object):
         else:
             self.dialect.validate_identifier(name)
 
-        return self.quote(name)
+        if not _alembic_quote:
+            return name
+        else:
+            return self.quote(name)
 
     def format_index(self, index):
         return self.format_constraint(index)