Backport rsim#1962 to release50 branch

Updated manually because there is a git conflict to backport rsim#1962 to release52.

lib/active_record/connection_adapters/oracle_enhanced/database_statements.rb

@@ -263,7 +263,7 @@ def write_lobs(table_name, klass, attributes, columns) #:nodoc:
               value = klass.attribute_types[col.name].serialize(value)
             end
             uncached do
-              unless lob_record = select_one(<<-SQL.strip.gsub(/\s+/, " "), "Writable Large Object")
+              unless lob_record = select_one(sql = <<-SQL.strip.gsub(/\s+/, " "), "Writable Large Object")
                 SELECT #{quote_column_name(col.name)} FROM #{quote_table_name(table_name)}
                 WHERE #{quote_column_name(klass.primary_key)} = #{id} FOR UPDATE
               SQL