Result Set Packets

MariaDB Server sends the following packets as part of a result set.

A result set consists of different packets:

• Result set metadata.

  • 1 column count packet.

• If not (MARIADB_CLIENT_CACHE_METADATA capability set) OR (send metadata == 1):

  • For each column (for instance, column_count times):

    • Column Definition packet.

• If not (CLIENT_DEPRECATE_EOF capability set) EOF_Packet.

• n result set row.

• If error:

  • ERR_Packet.

• Else:

  • If CLIENT_DEPRECATE_EOF capability:

    • OK_Packet with a 0xFE header.

  • Else EOF_Packet.

It would be unsafe to assume that any packet with a 0xFE header is an OK packet (OK_Packet) or an EOF packet (EOF_Packet), because result-set row packets (ResultsetRow) can also begin with 0xFE when using the text protocol with a field length greater than 0xFFFFFF. To safely confirm that a packet with a 0xFE header is an OK packet (OK_Packet) or an EOF packet (EOF_Packet), you must also check that the packet length is less than 0xFFFFFF.

Column Count Packet

The column count packet describes the number of columns in the result set. It uses the following format:

• int column count.

• If (MARIADB_CLIENT_CACHE_METADATA capability set):

  • int<1> metadata follows (0 / 1).

The metadata indicator byte is only present if both the client and the server declare the MARIADB_CLIENT_CACHE_METADATA capability.

If the metadata byte is set to 1, the normal metadata follows the column definitions. If the metadata byte is set to 0, the Column Count Packet is immediately followed by the second EOF packet (EOF_Packet) or the result set rows if the CLIENT_DEPRECATE_EOF capability is set.

Column Definition Packet

A column definition packet describes a column in the result set. It uses the following format:

• string catalog (always 'def').

• string schema.

• string table alias.

• string table.

• string column alias.

• string column.

• If extended type supported (see MARIADB_CLIENT_EXTENDED_METADATA ):

  • string extended metadata.

• int length of fixed fields (=0xC).

• int<2> character set number.

• int<4> max. column size.

• int<1> Field types.

• int<2> Field detail flag.

• int<1> decimals.

• int<2> - unused -

Field types

The column type field in the column definition packet describes the base type of the column. It also indicates how the values are encoded for COM_STMT_EXECUTE parameters and binary result set rows.

Value	Protocol Column Type	Encoding
0	MYSQL_TYPE_DECIMAL	byte encoding
1	MYSQL_TYPE_TINY	TINYINT Binary encoding
2	MYSQL_TYPE_SHORT	SMALLINT Binary encoding
3	MYSQL_TYPE_LONG	INTEGER Binary encoding
4	MYSQL_TYPE_FLOAT	FLOAT Binary encoding
5	MYSQL_TYPE_DOUBLE	DOUBLE Binary encoding
6	MYSQL_TYPE_NULL	Not used, nullness is indicated by the NULL-bitmap in the result
7	MYSQL_TYPE_TIMESTAMP	TIMESTAMP Binary encoding
8	MYSQL_TYPE_LONGLONG	BIGINT Binary encoding
9	MYSQL_TYPE_INT24	INTEGER Binary encoding
10	MYSQL_TYPE_DATE	TIMESTAMP Binary encoding
11	MYSQL_TYPE_TIME	TIME Binary encoding
12	MYSQL_TYPE_DATETIME	TIMESTAMP Binary encoding
13	MYSQL_TYPE_YEAR	SMALLINT Binary encoding
14	MYSQL_TYPE_NEWDATE	byte encoding
15	MYSQL_TYPE_VARCHAR	byte encoding
16	MYSQL_TYPE_BIT	byte encoding
17	MYSQL_TYPE_TIMESTAMP2	Used only in the replication protocol
18	MYSQL_TYPE_DATETIME2	Used only in the replication protocol
19	MYSQL_TYPE_TIME2	Used only in the replication protocol
245	MYSQL_TYPE_JSON	byte encoding (only used with MySQL, MariaDB uses MYSQL_TYPE_STRING for JSON)
246	MYSQL_TYPE_NEWDECIMAL	byte encoding
247	MYSQL_TYPE_ENUM	byte encoding
248	MYSQL_TYPE_SET	byte encoding
249	MYSQL_TYPE_TINY_BLOB	byte encoding
250	MYSQL_TYPE_MEDIUM_BLOB	byte encoding
251	MYSQL_TYPE_LONG_BLOB	byte encoding
252	MYSQL_TYPE_BLOB	byte encoding
253	MYSQL_TYPE_VAR_STRING	byte encoding
254	MYSQL_TYPE_STRING	byte encoding
255	MYSQL_TYPE_GEOMETRY	byte encoding

Field Details Flag

The column details flag describes certain column attributes and whether certain column options are set.

It is a bitmask with the following flags:

Flag Value	Flag Name	Flag Description
1	NOT_NULL	field cannot be null
2	PRIMARY_KEY	field is a primary key
4	UNIQUE_KEY	field is unique
8	MULTIPLE_KEY	field is in a multiple key
16	BLOB	is this field a Blob
32	UNSIGNED	is this field unsigned
64	ZEROFILL_FLAG	is this field a zerofill
128	BINARY_COLLATION	whether this field has a binary collation
256	ENUM	Field is an enumeration
512	AUTO_INCREMENT	field auto-increment
1024	TIMESTAMP	field is a timestamp value
2048	SET	field is a SET
4096	NO_DEFAULT_VALUE_FLAG	field doesn't have default value
8192	ON_UPDATE_NOW_FLAG	field is set to NOW on UPDATE
32768	NUM_FLAG	field is num

The BLOB flag cannot be used to determine if a column has binary data, because BINARY and VARBINARY columns are treated as strings, instead of blobs.

The BINARY_COLLATION flag can be used to determine if a string column has binary data.

Extended Metadata

This extended column type information can be used to find out more specific details about the column type:

• For a POINT column, the column type field is MYSQL_TYPE_GEOMETRY, but the extended type indicates 'point'.

• For a JSON column, the column type field is MYSQL_TYPE_STRING, but the extended type indicates 'json'.

• While string has data:

  • int<1> data type: 0x00:type, 0x01: format.

  • string value.

_{This page is licensed: CC BY-SA / Gnu FDL}