For binlog version 4. More...

#include <control_events.h>

Inheritance diagram for mysql::binlog::event::Format_description_event:

Public Member Functions
	Format_description_event (uint8_t binlog_ver, const char *server_ver)
	Format_description_event 1st constructor. More...

	Format_description_event (const char buf, const Format_description_event fde)
	The layout of Format_description_event data part is as follows: More...

	Format_description_event (const Format_description_event &)=default

Format_description_event &	operator= (const Format_description_event &)=default

unsigned long	get_product_version () const
	This method is used to find out the version of server that originated the current FD instance. More...

bool	is_version_before_checksum () const
	This method checks the MySQL version to determine whether checksums may be present in the events contained in the binary log. More...

void	calc_server_version_split ()
	This method populates the array server_version_split which is then used for lookups to find if the server which created this event has some known bug. More...

	~Format_description_event () override

bool	header_is_valid () const

bool	version_is_valid () const

Public Member Functions inherited from mysql::binlog::event::Binary_log_event
virtual	~Binary_log_event ()=0

	Binary_log_event (const Binary_log_event &)=default

	Binary_log_event (Binary_log_event &&)=default

Binary_log_event &	operator= (const Binary_log_event &)=default

Binary_log_event &	operator= (Binary_log_event &&)=default

enum Log_event_type	get_event_type () const
	Helper method. More...

const Log_event_header *	header () const
	Return a const pointer to the header of the log event. More...

Log_event_header *	header ()
	Return a non-const pointer to the header of the log event. More...

const Log_event_footer *	footer () const
	Return a const pointer to the footer of the log event. More...

Log_event_footer *	footer ()
	Return a non-const pointer to the footer of the log event. More...

Event_reader &	reader ()
	Returns a reference to the event Event_reader object. More...

Public Attributes
time_t	created
	If this event is at the start of the first binary log since server startup 'created' should be the timestamp when the event (and the binary log) was created. More...

uint16_t	binlog_version

char	server_version [ST_SERVER_VER_LEN]

bool	dont_set_created

uint8_t	common_header_len
	The size of the fixed header which all events have (for binlogs written by this version, this is equal to LOG_EVENT_HEADER_LEN), except FORMAT_DESCRIPTION_EVENT and ROTATE_EVENT (those have a header of size LOG_EVENT_MINIMAL_HEADER_LEN). More...

std::vector< uint8_t >	post_header_len

unsigned char	server_version_split [ST_SERVER_VER_SPLIT_LEN]

uint8_t	number_of_event_types

Additional Inherited Members
Public Types inherited from mysql::binlog::event::Binary_log_event
enum	enum_post_header_length { QUERY_HEADER_MINIMAL_LEN = (4 + 4 + 1 + 2) , QUERY_HEADER_LEN = (QUERY_HEADER_MINIMAL_LEN + 2) , STOP_HEADER_LEN = 0 , START_V3_HEADER_LEN = (2 + ST_SERVER_VER_LEN + 4) , ROTATE_HEADER_LEN = 8 , INTVAR_HEADER_LEN = 0 , APPEND_BLOCK_HEADER_LEN = 4 , DELETE_FILE_HEADER_LEN = 4 , RAND_HEADER_LEN = 0 , USER_VAR_HEADER_LEN = 0 , FORMAT_DESCRIPTION_HEADER_LEN = (START_V3_HEADER_LEN + 1 + LOG_EVENT_TYPES) , XID_HEADER_LEN = 0 , BEGIN_LOAD_QUERY_HEADER_LEN = APPEND_BLOCK_HEADER_LEN , ROWS_HEADER_LEN_V1 = 8 , TABLE_MAP_HEADER_LEN = 8 , EXECUTE_LOAD_QUERY_EXTRA_HEADER_LEN = (4 + 4 + 4 + 1) , EXECUTE_LOAD_QUERY_HEADER_LEN , INCIDENT_HEADER_LEN = 2 , HEARTBEAT_HEADER_LEN = 0 , IGNORABLE_HEADER_LEN = 0 , ROWS_HEADER_LEN_V2 = 10 , TRANSACTION_CONTEXT_HEADER_LEN = 18 , VIEW_CHANGE_HEADER_LEN = 52 , XA_PREPARE_HEADER_LEN = 0 , TRANSACTION_PAYLOAD_HEADER_LEN = 0 }
	The lengths for the fixed data part of each event. More...

Static Public Attributes inherited from mysql::binlog::event::Binary_log_event
static const int	LOG_EVENT_TYPES = (ENUM_END_EVENT - 1)

Protected Member Functions inherited from mysql::binlog::event::Binary_log_event
	Binary_log_event (Log_event_type type_code)
	This constructor is used to initialize the type_code of header object m_header. More...

	Binary_log_event (const char *buf, const Format_description_event fde)
	This constructor will create a new object of Log_event_header and initialize the variable m_header, which in turn will be used to initialize Log_event's member common_header. More...

Detailed Description

For binlog version 4.

This event is saved by threads which read it, as they need it for future use (to decode the ordinary events).

Binary Format

The Post-Header has six components:

Post-Header for Format_description_event
Name	Format	Description
created	4 byte unsigned integer	The creation timestamp, if non-zero, is the time in seconds when this event was created
binlog_version	2 byte unsigned integer	This is 1 in MySQL 3.23 and 3 in MySQL 4.0 and 4.1 (In MySQL 5.0 and up, FORMAT_DESCRIPTION_EVENT is used instead of START_EVENT_V3 and for them its 4).
server_version	char array of 50 bytes	The MySQL server's version (example: 4.0.14-debug-log), padded with 0x00 bytes on the right
common_header_len	1 byte unsigned integer	The length of the event header. This value includes the extra_headers field, so this header length - 19 yields the size of the extra_headers field.
post_header_len	array of type 1 byte unsigned integer	The lengths for the fixed data part of each event
server_version_split	unsigned char array	Stores the server version of the server and splits them in three parts
number_of_event_types	1 byte unsigned integer	number of event types present in the server

Constructor & Destructor Documentation

◆ Format_description_event() [1/3]

mysql::binlog::event::Format_description_event::Format_description_event	(	uint8_t	binlog_ver,
		const char *	server_ver
	)

Format_description_event 1st constructor.

This constructor can be used to create the event to write to the binary log (when the server starts or when FLUSH LOGS)

Parameters

binlog_ver	the binlog version for which we want to build an event. It should only be 4, old versions are not compatible anymore since 8.0.2.
server_ver	The MySQL server's version.

This will be used to initialize the post_header_len, for binlog version 4.

◆ Format_description_event() [2/3]

mysql::binlog::event::Format_description_event::Format_description_event	(	const char *	buf,
		const Format_description_event *	fde
	)

The layout of Format_description_event data part is as follows:

The problem with this constructor is that the fixed header may have a length different from this version, but we don't know this length as we have not read the Format_description_log_event which says it, yet.

+=====================================+
| event  | binlog_version   19 : 2    | = 4
| data   +----------------------------+
|        | server_version   21 : 50   |
|        +----------------------------+
|        | create_timestamp 71 : 4    |
|        +----------------------------+
|        | header_length    75 : 1    |
|        +----------------------------+
|        | post-header      76 : n    | = array of n bytes, one byte
|        | lengths for all            |   per event type that the
|        | event types                |   server knows about
+=====================================+

Parameters

buf	Contains the serialized event.
fde	An FDE event (see Rotate_event constructor for more info).

Note: The fde passed to this constructor was created through another constructor of FDE class.

This length is in the post-header of the event, but we don't know where the post-header starts.

So this type of event HAS to:

either have the header's length at the beginning (in the header, at a fixed position which will never be changed), not in the post-header. That would make the header be "shifted" compared to other events.
or have a header of size LOG_EVENT_MINIMAL_HEADER_LEN (19), in all future versions, so that we know for sure.

I (Guilhem) chose the 2nd solution. Rotate has the same constraint (because it is sent before Format_description_log_event).

◆ Format_description_event() [3/3]

mysql::binlog::event::Format_description_event::Format_description_event ( const Format_description_event & )

default

◆ ~Format_description_event()

mysql::binlog::event::Format_description_event::~Format_description_event ( )

overridedefault

Member Function Documentation

◆ calc_server_version_split()

void mysql::binlog::event::Format_description_event::calc_server_version_split ( )

This method populates the array server_version_split which is then used for lookups to find if the server which created this event has some known bug.

◆ get_product_version()

unsigned long mysql::binlog::event::Format_description_event::get_product_version ( ) const

This method is used to find out the version of server that originated the current FD instance.

Returns: the version of server.; the version of server

◆ header_is_valid()

bool mysql::binlog::event::Format_description_event::header_is_valid ( ) const

inline

◆ is_version_before_checksum()

bool mysql::binlog::event::Format_description_event::is_version_before_checksum ( ) const

This method checks the MySQL version to determine whether checksums may be present in the events contained in the binary log.

This method checks the MySQL version to determine whether checksums may be present in the events contained in the bainry log.

Return values

true	if the event's version is earlier than one that introduced the replication event checksum.
false	otherwise.

◆ operator=()

Format_description_event & mysql::binlog::event::Format_description_event::operator= ( const Format_description_event & )

default

◆ version_is_valid()

bool mysql::binlog::event::Format_description_event::version_is_valid ( ) const

inline

Member Data Documentation

◆ binlog_version

uint16_t mysql::binlog::event::Format_description_event::binlog_version

◆ common_header_len

uint8_t mysql::binlog::event::Format_description_event::common_header_len

The size of the fixed header which all events have (for binlogs written by this version, this is equal to LOG_EVENT_HEADER_LEN), except FORMAT_DESCRIPTION_EVENT and ROTATE_EVENT (those have a header of size LOG_EVENT_MINIMAL_HEADER_LEN).

◆ created

time_t mysql::binlog::event::Format_description_event::created

If this event is at the start of the first binary log since server startup 'created' should be the timestamp when the event (and the binary log) was created.

In the other case (i.e. this event is at the start of a binary log created by FLUSH LOGS or automatic rotation), 'created' should be 0. This "trick" is used by MySQL >=4.0.14 slaves to know whether they must drop stale temporary tables and whether they should abort unfinished transaction.

Note that when 'created'!=0, it is always equal to the event's timestamp; indeed Format_description_event is written only in binlog.cc where the first constructor below is called, in which 'created' is set to 'when'. So in fact 'created' is a useless variable. When it is 0 we can read the actual value from timestamp ('when') and when it is non-zero we can read the same value from timestamp ('when'). Conclusion:

we use timestamp to print when the binlog was created.
we use 'created' only to know if this is a first binlog or not.

◆ dont_set_created

bool mysql::binlog::event::Format_description_event::dont_set_created

◆ number_of_event_types

uint8_t mysql::binlog::event::Format_description_event::number_of_event_types

◆ post_header_len

std::vector<uint8_t> mysql::binlog::event::Format_description_event::post_header_len

◆ server_version

char mysql::binlog::event::Format_description_event::server_version[ST_SERVER_VER_LEN]

◆ server_version_split

unsigned char mysql::binlog::event::Format_description_event::server_version_split[ST_SERVER_VER_SPLIT_LEN]

The documentation for this class was generated from the following files:

libs/mysql/binlog/event/control_events.h
libs/mysql/binlog/event/control_events.cpp

Public Member Functions

Public Attributes

Additional Inherited Members