System_table_access Class Reference

A base class for accessing a system table. More...

#include <rpl_table_access.h>

Inheritance diagram for System_table_access:

Public Member Functions
virtual	~System_table_access ()=default
bool	open_table (THD *thd, const LEX_CSTRING dbstr, const LEX_CSTRING tbstr, uint max_num_field, enum thr_lock_type lock_type, TABLE **table, Open_tables_backup *backup)
	Opens and locks a system table. More...
bool	open_table (THD *thd, std::string dbstr, std::string tbstr, uint max_num_field, enum thr_lock_type lock_type, TABLE **table, Open_tables_backup *backup)
	Opens and locks a system table. More...
virtual void	before_open (THD *thd)=0
	Prepares before opening table. More...
bool	close_table (THD *thd, TABLE *table, Open_tables_backup *backup, bool error, bool need_commit)
	Commits the changes, unlocks the table and closes it. More...
THD *	create_thd ()
	Creates a new thread in the bootstrap process or in the mysqld startup, a thread is created in order to be able to access a table. More...
void	drop_thd (THD *thd)
	Destroys the created thread and restores the system_thread information. More...

Public Attributes
uint	m_flags

Detailed Description

A base class for accessing a system table.

Constructor & Destructor Documentation

~System_table_access()

virtual System_table_access::~System_table_access ( )

virtualdefault

Member Function Documentation

before_open()

virtual void System_table_access::before_open ( THD *  thd )

pure virtual

Prepares before opening table.

Parameters

[in]

thd

Thread requesting to open the table

Implemented in Gtid_table_access_context, and Rpl_info_table_access.

close_table()

bool System_table_access::close_table	(	THD *	thd,
		TABLE *	table,
		Open_tables_backup *	backup,
		bool	error,
		bool	need_commit
	)

Commits the changes, unlocks the table and closes it.

This method needs to be called even if the open_table fails, in order to ensure the lock info is properly restored.

Parameters

[in]	thd	Thread requesting to close the table
[in]	table	Table to be closed
[in]	backup	Restore the lock info from here
[in]	error	If there was an error while updating the table
[in]	need_commit	Need to commit current transaction if it is true.

Return values

true	failed
false	success

If there is an error, rolls back the current statement. Otherwise, commits it. However, if a new thread was created and there is an error, the transaction must be rolled back. Otherwise, it must be committed. In this case, the changes were not done on behalf of any user transaction and if not finished, there would be pending changes.

create_thd()

THD * System_table_access::create_thd

(

)

Creates a new thread in the bootstrap process or in the mysqld startup, a thread is created in order to be able to access a table.

Returns

THD* Pointer to thread structure

drop_thd()

void System_table_access::drop_thd

(

THD *

thd

)

Destroys the created thread and restores the system_thread information.

Parameters

thd	Thread requesting to be destroyed

open_table() [1/2]

bool System_table_access::open_table	(	THD *	thd,
		const LEX_CSTRING	dbstr,
		const LEX_CSTRING	tbstr,
		uint	max_num_field,
		enum thr_lock_type	lock_type,
		TABLE **	table,
		Open_tables_backup *	backup
	)

Opens and locks a system table.

It's assumed that the caller knows what they are doing:

• whether it was necessary to reset-and-backup the open tables state
• whether the requested lock does not lead to a deadlock
• whether this open mode would work under LOCK TABLES, or inside a stored function or trigger.

Note that if the table can't be locked successfully this operation will close it. Therefore it provides guarantee that it either opens and locks table or fails without leaving any tables open.

Parameters

[in]	thd	Thread requesting to open the table
[in]	dbstr	Database where the table resides
[in]	tbstr	Table to be opened
[in]	max_num_field	Maximum number of fields
[in]	lock_type	How to lock the table
[out]	table	We will store the open table here
[out]	backup	Save the lock info. here

Return values

true	open and lock failed - an error message is pushed into the stack
false	success

open_table() [2/2]

bool System_table_access::open_table	(	THD *	thd,
		std::string	dbstr,
		std::string	tbstr,
		uint	max_num_field,
		enum thr_lock_type	lock_type,
		TABLE **	table,
		Open_tables_backup *	backup
	)

Opens and locks a system table.

It's assumed that the caller knows what they are doing:

• whether it was necessary to reset-and-backup the open tables state
• whether the requested lock does not lead to a deadlock
• whether this open mode would work under LOCK TABLES, or inside a stored function or trigger.

Note that if the table can't be locked successfully this operation will close it. Therefore it provides guarantee that it either opens and locks table or fails without leaving any tables open.

Parameters

[in]	thd	Thread requesting to open the table
[in]	dbstr	Database where the table resides
[in]	tbstr	Table to be opened
[in]	max_num_field	Maximum number of fields
[in]	lock_type	How to lock the table
[out]	table	We will store the open table here
[out]	backup	Save the lock info. here

Return values

true	open and lock failed - an error message is pushed into the stack
false	success

Member Data Documentation

m_flags

uint System_table_access::m_flags

---

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

• sql/rpl_table_access.h
• sql/rpl_table_access.cc