Fix bulk_batch_size

plus a small fix for bulk_update

Issue #71, large bulk_batch_size cause queries exceeding 2100 parameters limit.

Author: absci

mssql/functions.py

@@ -259,7 +259,7 @@ def bulk_update_with_default(self, objs, fields, batch_size=None, default=0):
                     attr = Value(attr, output_field=field)
                 when_statements.append(When(pk=obj.pk, then=attr))
             if(value_none_counter == len(when_statements)):
-                case_statement = Case(*when_statements, output_field=field, default=default)
+                case_statement = Case(*when_statements, output_field=field, default=Value(default))
             else:
                 case_statement = Case(*when_statements, output_field=field)
             if requires_casting:

mssql/operations.py

@@ -62,7 +62,8 @@ def bulk_batch_size(self, fields, objs):
         # up 2 parameters but I've had this error when sending 2098 parameters.
         max_query_params = 2050
         # inserts are capped at 1000 rows regardless of number of query params.
-        return min(max_insert_rows, max_query_params // fields_len)
+        # bulk_update CASE...WHEN...THEN statement sometimes takes 2 parameters per field
+        return min(max_insert_rows, max_query_params // fields_len // 2)
 
     def bulk_insert_sql(self, fields, placeholder_rows):
         placeholder_rows_sql = (", ".join(row) for row in placeholder_rows)