Class FieldDescriptorPacket

pymysql/protocol.py:225–276

A MysqlPacket that represents a specific column's metadata in the result. Parsing is automatically done and the results are exported via public attributes on the class such as: db, table_name, name, length, type_code.

class FieldDescriptorPacket(MysqlPacket):
    """A MysqlPacket that represents a specific column's metadata in the result.

    Parsing is automatically done and the results are exported via public
    attributes on the class such as: db, table_name, name, length, type_code.
    """

    def __init__(self, data, encoding):
        MysqlPacket.__init__(self, data, encoding)
        self._parse_field_descriptor(encoding)

    def _parse_field_descriptor(self, encoding):
        """Parse the 'Field Descriptor' (Metadata) packet.

        This is compatible with MySQL 4.1+ (not compatible with MySQL 4.0).
        """
        self.catalog = self.read_length_coded_string()
        self.db = self.read_length_coded_string()
        self.table_name = self.read_length_coded_string().decode(encoding)
        self.org_table = self.read_length_coded_string().decode(encoding)
        self.name = self.read_length_coded_string().decode(encoding)
        self.org_name = self.read_length_coded_string().decode(encoding)
        (
            self.charsetnr,
            self.length,
            self.type_code,
            self.flags,
            self.scale,
        ) = self.read_struct("<xHIBHBxx")
        # 'default' is a length coded binary and is still in the buffer?
        # not used for normal result sets...

    def description(self):
        """Provides a 7-item tuple compatible with the Python PEP249 DB Spec."""
        return (
            self.name,
            self.type_code,
            None,  # TODO: display_length; should this be self.length?
            self.get_column_length(),  # 'internal_size'
            self.get_column_length(),  # 'precision'  # TODO: why!?!?
            self.scale,
            self.flags % 2 == 0,
        )

    def get_column_length(self):
        if self.type_code == FIELD_TYPE.VAR_STRING:
            mblen = MBLENGTH.get(self.charsetnr, 1)
            return self.length // mblen
        return self.length

    def __str__(self):
        return f"{self.__class__} {self.db!r}.{self.table_name!r}.{self.name!r}, type={self.type_code}, flags={self.flags:x}"


class OKPacketWrapper: