why the TableMapEvent pased by _ctl_connection

why the TableMapEvent pased by _ctl_connection from master?Not parse from binlog?Beacuse when we has more than 10 thousand records import into mysql .It 's very slow.
The code is in pymysqlreplication.row_event.TableMapEvent class at line 579~582;
` if self.table_id in table_map:
self.column_schemas = table_map[self.table_id].column_schemas
else:
self.column_schemas = self._ctl_connection._get_table_information(self.schema, self.table)
`
the self.table_id property is always {}.

Start in pymysqlreplication.row_event.TableMapEvent around lines 579–582 and trace how table_map and table_id are populated before this branch. Compare that path with binlog TableMapEvent handling during a large import; the issue is done when the empty table_id behavior and resulting slow metadata lookups are explained and addressed.

Written by the indexing model from the issue text.