Locked_tables_list Class Reference

Tables that were locked with LOCK TABLES statement. More...

#include <locked_tables_list.h>

Classes
struct	MDL_ticket_pair

Public Member Functions
	Locked_tables_list ()
void	unlock_locked_tables (THD *thd)
	Leave LTM_LOCK_TABLES mode if it's been entered. More...
	~Locked_tables_list ()
bool	init_locked_tables (THD *thd)
	Enter LTM_LOCK_TABLES mode. More...
Table_ref *	locked_tables () const
void	unlink_from_list (const THD *thd, Table_ref *table_list, bool remove_from_locked_tables)
	Unlink a locked table from the locked tables list, either temporarily or permanently. More...
void	unlink_all_closed_tables (THD *thd, MYSQL_LOCK *lock, size_t reopen_count)
	This is an attempt to recover (somewhat) in case of an error. More...
bool	reopen_tables (THD *thd)
	Reopen the tables locked with LOCK TABLES and temporarily closed by a DDL statement or FLUSH TABLES. More...
void	rename_locked_table (Table_ref *old_table_list, const char *new_db, const char *new_table_name, MDL_ticket *target_mdl_ticket)
	Update database and table names of table locked with LOCK TABLES after table rename. More...
void	add_rename_tablespace_mdls (MDL_ticket *src, MDL_ticket *dst)
void	adjust_renamed_tablespace_mdls (MDL_context *mctx)
void	discard_renamed_tablespace_mdls ()

Private Types
using	MDL_ticket_pairs = std::vector< MDL_ticket_pair >

Private Attributes
MEM_ROOT	m_locked_tables_root
Table_ref *	m_locked_tables
Table_ref **	m_locked_tables_last
TABLE **	m_reopen_array
	An auxiliary array used only in reopen_tables(). More...
size_t	m_locked_tables_count
	Count the number of tables in m_locked_tables list. More...
MDL_ticket_pairs	m_rename_tablespace_mdls

Detailed Description

Tables that were locked with LOCK TABLES statement.

Encapsulates a list of Table_ref instances for tables locked by LOCK TABLES statement, memory root for metadata locks, and, generally, the context of LOCK TABLES statement.

In LOCK TABLES mode, the locked tables are kept open between statements. Therefore, we can't allocate metadata locks on execution memory root – as well as tables, the locks need to stay around till UNLOCK TABLES is called. The locks are allocated in the memory root encapsulated in this class.

Some SQL commands, like FLUSH TABLE or ALTER TABLE, demand that the tables they operate on are closed, at least temporarily. This class encapsulates a list of Table_ref instances, one for each base table from LOCK TABLES list, which helps conveniently close the TABLEs when it's necessary and later reopen them.

Member Typedef Documentation

MDL_ticket_pairs

using Locked_tables_list::MDL_ticket_pairs = std::vector<MDL_ticket_pair>

private

Constructor & Destructor Documentation

Locked_tables_list()

Locked_tables_list::Locked_tables_list

(

)

~Locked_tables_list()

Locked_tables_list::~Locked_tables_list ( )

inline

Member Function Documentation

add_rename_tablespace_mdls()

void Locked_tables_list::add_rename_tablespace_mdls	(	MDL_ticket *	src,
		MDL_ticket *	dst
	)

adjust_renamed_tablespace_mdls()

void Locked_tables_list::adjust_renamed_tablespace_mdls

(

MDL_context *

mctx

)

discard_renamed_tablespace_mdls()

void Locked_tables_list::discard_renamed_tablespace_mdls ( )

inline

init_locked_tables()

bool Locked_tables_list::init_locked_tables

(

THD *

thd

)

Enter LTM_LOCK_TABLES mode.

Enter the LOCK TABLES mode using all the tables that are currently open and locked in this connection. Initializes a Table_ref instance for every locked table.

Parameters

thd	thread handle

Returns

true if out of memory.

Sic: remember the actual table level lock type taken, to acquire the exact same type in reopen_tables(). E.g. if the table was locked for write, src_table_list->lock_type is TL_WRITE_DEFAULT, whereas reginfo.lock_type has been updated from thd->update_lock_default.

Allocate an auxiliary array to pass to mysql_lock_tables() in reopen_tables(). reopen_tables() is a critical path and we don't want to complicate it with extra allocations.

locked_tables()

Table_ref * Locked_tables_list::locked_tables ( ) const

inline

rename_locked_table()

void Locked_tables_list::rename_locked_table	(	Table_ref *	old_table_list,
		const char *	new_db,
		const char *	new_table_name,
		MDL_ticket *	target_mdl_ticket
	)

Update database and table names of table locked with LOCK TABLES after table rename.

Parameters

old_table_list	Table list element representing old db/table name.
new_db	Table's new database.
new_table_name	Table's new name.
target_mdl_ticket	Ticket representing metadata lock acquired on new table name.

Note

This function is a no-op if we're not under LOCK TABLES.

reopen_tables()

bool Locked_tables_list::reopen_tables

(

THD *

thd

)

Reopen the tables locked with LOCK TABLES and temporarily closed by a DDL statement or FLUSH TABLES.

Note

This function is a no-op if we're not under LOCK TABLES.

Returns

true if an error reopening the tables. May happen in case of some fatal system error only, e.g. a disk corruption, out of memory or a serious bug in the locking.

unlink_all_closed_tables()

void Locked_tables_list::unlink_all_closed_tables	(	THD *	thd,
		MYSQL_LOCK *	lock,
		size_t	reopen_count
	)

This is an attempt to recover (somewhat) in case of an error.

If we failed to reopen a closed table, let's unlink it from the list and forget about it. From a user perspective that would look as if the server "lost" the lock on one of the locked tables.

Note

This function is a no-op if we're not under LOCK TABLES.

unlink_from_list()

void Locked_tables_list::unlink_from_list	(	const THD *	thd,
		Table_ref *	table_list,
		bool	remove_from_locked_tables
	)

Unlink a locked table from the locked tables list, either temporarily or permanently.

Parameters

thd	thread handle
table_list	the element of locked tables list. The implementation assumes that this argument points to a Table_ref element linked into the locked tables list. Passing a Table_ref instance that is not part of locked tables list will lead to a crash.
remove_from_locked_tables	true if the table is removed from the list permanently.

This function is a no-op if we're not under LOCK TABLES.

See also

Locked_tables_list::reopen_tables()

unlock_locked_tables()

void Locked_tables_list::unlock_locked_tables

(

THD *

thd

)

Leave LTM_LOCK_TABLES mode if it's been entered.

Close all locked tables, free memory, and leave the mode.

Note

This function is a no-op if we're not in LOCK TABLES.

Member Data Documentation

m_locked_tables

Table_ref* Locked_tables_list::m_locked_tables

private

m_locked_tables_count

size_t Locked_tables_list::m_locked_tables_count

private

Count the number of tables in m_locked_tables list.

We can't rely on thd->lock->table_count because it excludes non-transactional temporary tables. We need to know an exact number of TABLE objects.

m_locked_tables_last

Table_ref** Locked_tables_list::m_locked_tables_last

private

m_locked_tables_root

MEM_ROOT Locked_tables_list::m_locked_tables_root

private

Initial value:

{key_memory_locked_table_list,
                                MEM_ROOT_BLOCK_SIZE}

m_rename_tablespace_mdls

MDL_ticket_pairs Locked_tables_list::m_rename_tablespace_mdls

private

m_reopen_array

TABLE** Locked_tables_list::m_reopen_array

private

An auxiliary array used only in reopen_tables().

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

• sql/locked_tables_list.h
• sql/locked_tables_list.cc