visit_ForeignKeyDefinition

# File activerecord/lib/active_record/connection_adapters/abstract/schema_creation.rb, line 72
        def visit_ForeignKeyDefinition(o)
          sql = +<<~SQL
            CONSTRAINT #{quote_column_name(o.name)}
            FOREIGN KEY (#{quote_column_name(o.column)})
              REFERENCES #{quote_table_name(o.to_table)} (#{quote_column_name(o.primary_key)})
          SQL
          sql << " #{action_sql('DELETE', o.on_delete)}" if o.on_delete
          sql << " #{action_sql('UPDATE', o.on_update)}" if o.on_update
          sql
        end