why the TableMapEvent pased by _ctl_connection

[queryDuan]

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 {}.

[queryDuan]

cat binlog_time | uniq -c

This is the binlog-generate-time ,the qps is more then 600.

This is the time after parsed binlog ,the qps is lessthen 300.

[queryDuan]

Sorry!I may understand a bit wrong.
` self.columns = []

    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)

    if len(self.column_schemas) != 0:
        # Read columns meta data
        column_types = list(self.packet.read(self.column_count))
        self.packet.read_length_coded_binary()
        for i in range(0, len(column_types)):
            column_type = column_types[i]
            try:
                column_schema = self.column_schemas[i]
            except IndexError:
                # this a dirty hack to prevent row events containing columns which have been dropped prior
                # to pymysqlreplication start, but replayed from binlog from blowing up the service.
                # TODO: this does not address the issue if the column other than the last one is dropped
                column_schema = {
                    'COLUMN_NAME': '__dropped_col_{i}__'.format(i=i),
                    'COLLATION_NAME': None,
                    'CHARACTER_SET_NAME': None,
                    'COLUMN_COMMENT': None,
                    'COLUMN_TYPE': 'BLOB',  # we don't know what it is, so let's not do anything with it.
                    'COLUMN_KEY': '',
                }
            col = Column(byte2int(column_type), column_schema, from_packet)
            self.columns.append(col)

    self.table_obj = Table(self.column_schemas, self.table_id, self.schema,
                           self.table, self.columns)`

In TableMapEvent class.
I mean that:How Can I get the table infomation only from binlog,not from master.beacuse the reall mysql-slave don't do it like that.And It's very fast!

[bjoernhaeuser]

If you search for issues in this repository it already has been discussed several times ;) The binlog simply does not carry these information.

See #197, #199, #163, #176

[queryDuan]

thak you!but why the reall mysql-slave don't need get table scheme info from master?Or that,we can only get onece,if we Continue to operate on the same table.

[queryDuan]

sorry!It's my wrong!Only fetch One scheme_info.But why It's so slowly?I wan't to find the reason!

[rspadim]

maybe cause information_schema is slower than show columns command?