Add multivalued insert context for defaultsticket_4075

wip

Change-Id: I6894c7b4a2bce3e83c3ade8af0e5b2f8df37b785
Fixes: #4075

1 files changed, 30 insertions, 3 deletions

diff --git a/lib/sqlalchemy/engine/default.py b/lib/sqlalchemy/engine/default.py
index 227ff0845..7d7e7fc2f 100644
--- a/lib/sqlalchemy/engine/default.py
+++ b/lib/sqlalchemy/engine/default.py
@@ -1177,10 +1177,11 @@ class DefaultExecutionContext(interfaces.ExecutionContext):
                 self.root_connection._handle_dbapi_exception(
                     e, None, None, None, self)
 
-    def _exec_default(self, default, type_):
+    def _exec_default(self, column, default, type_):
         if default.is_sequence:
             return self.fire_sequence(default, type_)
         elif default.is_callable:
+            self.current_column = column
             return default.arg(self)
         elif default.is_clause_element:
             # TODO: expensive branching here should be
@@ -1195,17 +1196,43 @@ class DefaultExecutionContext(interfaces.ExecutionContext):
         else:
             return default.arg
 
+    def get_current_parameters(self, isolate_multiinsert_groups=True):
+        try:
+            parameters = self.current_parameters
+            column = self.current_column
+        except AttributeError:
+            raise exc.InvalidRequestError(
+                "get_current_parameters() can only be invoked in the "
+                "context of a Python side column default function")
+        if isolate_multiinsert_groups and \
+            self.isinsert and \
+                self.compiled.statement._has_multi_parameters:
+            if column._is_multiparam_column:
+                index = column.index + 1
+                d = {column.original.key: parameters[column.key]}
+            else:
+                d = {column.key: parameters[column.key]}
+                index = 0
+            keys = self.compiled.statement.parameters[0].keys()
+            d.update(
+                (key, parameters["%s_m%d" % (key, index)])
+                for key in keys
+            )
+            return d
+        else:
+            return parameters
+
     def get_insert_default(self, column):
         if column.default is None:
             return None
         else:
-            return self._exec_default(column.default, column.type)
+            return self._exec_default(column, column.default, column.type)
 
     def get_update_default(self, column):
         if column.onupdate is None:
             return None
         else:
-            return self._exec_default(column.onupdate, column.type)
+            return self._exec_default(column, column.onupdate, column.type)
 
     def _process_executemany_defaults(self):
         key_getter = self.compiled._key_getters_for_crud_column[2]