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Backport of:
---------------------------------------------------------- revno: 2617.23.19 committer: Konstantin Osipov <kostja@sun.com> branch nick: mysql-6.0-runtime timestamp: Tue 2009-03-03 01:20:44 +0300 message: Metadata locking: realign comments. No semantical changes, only enforce a bit of the coding style. This is a review fix for WL#4284 "Transactional DDL locking". sql/mdl.cc: Realign doxygen comments. sql/mdl.h: Realign doxygen comments.
This commit is contained in:
Konstantin Osipov
parent
f477e66ec5
commit
97abce0e7c
2 changed files with 335 additions and 336 deletions
609
sql/mdl.cc
609
sql/mdl.cc
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@ -22,10 +22,10 @@
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/**
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The lock context. Created internally for an acquired lock.
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For a given name, there exists only one MDL_LOCK instance,
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and it exists only when the lock has been granted.
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Can be seen as an MDL subsystem's version of TABLE_SHARE.
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The lock context. Created internally for an acquired lock.
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For a given name, there exists only one MDL_LOCK instance,
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and it exists only when the lock has been granted.
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Can be seen as an MDL subsystem's version of TABLE_SHARE.
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*/
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struct MDL_LOCK
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@ -48,7 +48,7 @@ struct MDL_LOCK
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MDL_KEY key;
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/** List of granted tickets for this lock. */
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Ticket_list granted;
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/*
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/**
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There can be several upgraders and active exclusive
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belonging to the same context.
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*/
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@ -76,11 +76,11 @@ pthread_cond_t COND_mdl;
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HASH mdl_locks;
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/**
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Structure implementing global metadata lock. The only types
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of locks which are supported at the moment are shared and
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intention exclusive locks. Note that the latter type of global
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lock acquired automatically when one tries to acquire exclusive
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or shared upgradable lock on particular object.
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Structure implementing global metadata lock. The only types
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of locks which are supported at the moment are shared and
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intention exclusive locks. Note that the latter type of global
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lock acquired automatically when one tries to acquire exclusive
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or shared upgradable lock on particular object.
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*/
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struct MDL_GLOBAL_LOCK
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@ -102,21 +102,21 @@ mdl_locks_key(const uchar *record, size_t *length,
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/**
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Initialize the metadata locking subsystem.
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Initialize the metadata locking subsystem.
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This function is called at server startup.
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This function is called at server startup.
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In particular, initializes the new global mutex and
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the associated condition variable: LOCK_mdl and COND_mdl.
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These locking primitives are implementation details of the MDL
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subsystem and are private to it.
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In particular, initializes the new global mutex and
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the associated condition variable: LOCK_mdl and COND_mdl.
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These locking primitives are implementation details of the MDL
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subsystem and are private to it.
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Note, that even though the new implementation adds acquisition
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of a new global mutex to the execution flow of almost every SQL
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statement, the design capitalizes on that to later save on
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look ups in the table definition cache. This leads to reduced
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contention overall and on LOCK_open in particular.
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Please see the description of mdl_acquire_shared_lock() for details.
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Note, that even though the new implementation adds acquisition
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of a new global mutex to the execution flow of almost every SQL
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statement, the design capitalizes on that to later save on
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look ups in the table definition cache. This leads to reduced
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contention overall and on LOCK_open in particular.
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Please see the description of mdl_acquire_shared_lock() for details.
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*/
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void mdl_init()
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@ -131,10 +131,10 @@ void mdl_init()
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/**
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Release resources of metadata locking subsystem.
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Release resources of metadata locking subsystem.
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Destroys the global mutex and the condition variable.
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Called at server shutdown.
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Destroys the global mutex and the condition variable.
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Called at server shutdown.
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*/
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void mdl_destroy()
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@ -147,9 +147,9 @@ void mdl_destroy()
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/**
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Initialize a metadata locking context.
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Initialize a metadata locking context.
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This is to be called when a new server connection is created.
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This is to be called when a new server connection is created.
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*/
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void mdl_context_init(MDL_CONTEXT *context, THD *thd)
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@ -162,15 +162,15 @@ void mdl_context_init(MDL_CONTEXT *context, THD *thd)
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/**
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Destroy metadata locking context.
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Destroy metadata locking context.
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Assumes and asserts that there are no active or pending locks
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associated with this context at the time of the destruction.
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Assumes and asserts that there are no active or pending locks
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associated with this context at the time of the destruction.
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Currently does nothing. Asserts that there are no pending
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or satisfied lock requests. The pending locks must be released
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prior to destruction. This is a new way to express the assertion
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that all tables are closed before a connection is destroyed.
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Currently does nothing. Asserts that there are no pending
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or satisfied lock requests. The pending locks must be released
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prior to destruction. This is a new way to express the assertion
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that all tables are closed before a connection is destroyed.
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*/
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void mdl_context_destroy(MDL_CONTEXT *context)
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@ -182,13 +182,13 @@ void mdl_context_destroy(MDL_CONTEXT *context)
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/**
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Backup and reset state of meta-data locking context.
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Backup and reset state of meta-data locking context.
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mdl_context_backup_and_reset(), mdl_context_restore() and
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mdl_context_merge() are used by HANDLER implementation which
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needs to open table for new HANDLER independently of already
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open HANDLERs and add this table/metadata lock to the set of
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tables open/metadata locks for HANDLERs afterwards.
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mdl_context_backup_and_reset(), mdl_context_restore() and
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mdl_context_merge() are used by HANDLER implementation which
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needs to open table for new HANDLER independently of already
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open HANDLERs and add this table/metadata lock to the set of
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tables open/metadata locks for HANDLERs afterwards.
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*/
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void mdl_context_backup_and_reset(MDL_CONTEXT *ctx, MDL_CONTEXT *backup)
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@ -201,7 +201,7 @@ void mdl_context_backup_and_reset(MDL_CONTEXT *ctx, MDL_CONTEXT *backup)
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/**
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Restore state of meta-data locking context from backup.
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Restore state of meta-data locking context from backup.
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*/
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void mdl_context_restore(MDL_CONTEXT *ctx, MDL_CONTEXT *backup)
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@ -214,7 +214,7 @@ void mdl_context_restore(MDL_CONTEXT *ctx, MDL_CONTEXT *backup)
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/**
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Merge meta-data locks from one context into another.
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Merge meta-data locks from one context into another.
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*/
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void mdl_context_merge(MDL_CONTEXT *dst, MDL_CONTEXT *src)
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@ -247,32 +247,32 @@ void mdl_context_merge(MDL_CONTEXT *dst, MDL_CONTEXT *src)
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/**
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Initialize a lock request.
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Initialize a lock request.
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This is to be used for every lock request.
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This is to be used for every lock request.
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Note that initialization and allocation are split into two
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calls. This is to allow flexible memory management of lock
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requests. Normally a lock request is stored in statement memory
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(e.g. is a member of struct TABLE_LIST), but we would also like
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to allow allocation of lock requests in other memory roots,
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for example in the grant subsystem, to lock privilege tables.
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Note that initialization and allocation are split into two
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calls. This is to allow flexible memory management of lock
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requests. Normally a lock request is stored in statement memory
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(e.g. is a member of struct TABLE_LIST), but we would also like
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to allow allocation of lock requests in other memory roots,
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for example in the grant subsystem, to lock privilege tables.
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The MDL subsystem does not own or manage memory of lock requests.
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Instead it assumes that the life time of every lock request (including
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encompassed members db/name) encloses calls to mdl_request_add()
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and mdl_request_remove() or mdl_request_remove_all().
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The MDL subsystem does not own or manage memory of lock requests.
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Instead it assumes that the life time of every lock request (including
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encompassed members db/name) encloses calls to mdl_request_add()
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and mdl_request_remove() or mdl_request_remove_all().
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@param lock_req Pointer to an MDL_LOCK_REQUEST object to initialize
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@param type Id of type of object to be locked
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@param db Name of database to which the object belongs
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@param name Name of of the object
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@param lock_req Pointer to an MDL_LOCK_REQUEST object to initialize
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@param type Id of type of object to be locked
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@param db Name of database to which the object belongs
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@param name Name of of the object
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The initialized lock request will have MDL_SHARED type.
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The initialized lock request will have MDL_SHARED type.
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Suggested lock types: TABLE - 0 PROCEDURE - 1 FUNCTION - 2
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Note that tables and views must have the same lock type, since
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they share the same name space in the SQL standard.
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Suggested lock types: TABLE - 0 PROCEDURE - 1 FUNCTION - 2
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Note that tables and views must have the same lock type, since
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they share the same name space in the SQL standard.
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*/
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void mdl_request_init(MDL_LOCK_REQUEST *lock_req, unsigned char type,
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@ -285,21 +285,21 @@ void mdl_request_init(MDL_LOCK_REQUEST *lock_req, unsigned char type,
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/**
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Allocate and initialize one lock request.
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Allocate and initialize one lock request.
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Same as mdl_init_lock(), but allocates the lock and the key buffer
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on a memory root. Necessary to lock ad-hoc tables, e.g.
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mysql.* tables of grant and data dictionary subsystems.
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Same as mdl_init_lock(), but allocates the lock and the key buffer
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on a memory root. Necessary to lock ad-hoc tables, e.g.
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mysql.* tables of grant and data dictionary subsystems.
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@param type Id of type of object to be locked
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@param db Name of database to which object belongs
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@param name Name of of object
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@param root MEM_ROOT on which object should be allocated
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@param type Id of type of object to be locked
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@param db Name of database to which object belongs
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@param name Name of of object
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@param root MEM_ROOT on which object should be allocated
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@note The allocated lock request will have MDL_SHARED type.
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@note The allocated lock request will have MDL_SHARED type.
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@retval 0 Error
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@retval non-0 Pointer to an object representing a lock request
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@retval 0 Error if out of memory
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@retval non-0 Pointer to an object representing a lock request
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*/
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MDL_LOCK_REQUEST *
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@ -319,19 +319,19 @@ mdl_request_alloc(unsigned char type, const char *db,
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/**
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Add a lock request to the list of lock requests of the context.
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Add a lock request to the list of lock requests of the context.
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The procedure to acquire metadata locks is:
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- allocate and initialize lock requests (mdl_request_alloc())
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- associate them with a context (mdl_request_add())
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- call mdl_acquire_shared_lock()/mdl_ticket_release() (maybe repeatedly).
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The procedure to acquire metadata locks is:
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- allocate and initialize lock requests (mdl_request_alloc())
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- associate them with a context (mdl_request_add())
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- call mdl_acquire_shared_lock()/mdl_ticket_release() (maybe repeatedly).
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Associates a lock request with the given context.
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Associates a lock request with the given context.
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@param context The MDL context to associate the lock with.
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There should be no more than one context per
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connection, to avoid deadlocks.
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@param lock_req The lock request to be added.
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@param context The MDL context to associate the lock with.
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There should be no more than one context per
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connection, to avoid deadlocks.
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@param lock_req The lock request to be added.
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*/
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void mdl_request_add(MDL_CONTEXT *context, MDL_LOCK_REQUEST *lock_req)
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@ -344,18 +344,18 @@ void mdl_request_add(MDL_CONTEXT *context, MDL_LOCK_REQUEST *lock_req)
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/**
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Remove a lock request from the list of lock requests.
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Remove a lock request from the list of lock requests.
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Disassociates a lock request from the given context.
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Disassociates a lock request from the given context.
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@param context The MDL context to remove the lock from.
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@param lock_req The lock request to be removed.
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@param context The MDL context to remove the lock from.
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@param lock_req The lock request to be removed.
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@pre The lock request being removed should correspond to a ticket that
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was released or was not acquired.
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@pre The lock request being removed should correspond to a ticket that
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was released or was not acquired.
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@note Resets lock request back to its initial state
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(i.e. sets type to MDL_SHARED).
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@note Resets lock request back to its initial state
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(i.e. sets type to MDL_SHARED).
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*/
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void mdl_request_remove(MDL_CONTEXT *context, MDL_LOCK_REQUEST *lock_req)
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@ -370,12 +370,12 @@ void mdl_request_remove(MDL_CONTEXT *context, MDL_LOCK_REQUEST *lock_req)
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/**
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Clear all lock requests in the context.
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Disassociates lock requests from the context.
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Clear all lock requests in the context.
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Disassociates lock requests from the context.
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Also resets lock requests back to their initial state (i.e. MDL_SHARED).
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Also resets lock requests back to their initial state (i.e. MDL_SHARED).
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@param context Context to be cleared.
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@param context Context to be cleared.
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*/
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void mdl_request_remove_all(MDL_CONTEXT *context)
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@ -393,10 +393,10 @@ void mdl_request_remove_all(MDL_CONTEXT *context)
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/**
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Auxiliary functions needed for creation/destruction of MDL_LOCK objects.
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Auxiliary functions needed for creation/destruction of MDL_LOCK objects.
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@todo This naive implementation should be replaced with one that saves
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on memory allocation by reusing released objects.
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@todo This naive implementation should be replaced with one that saves
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on memory allocation by reusing released objects.
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*/
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static MDL_LOCK* alloc_lock_object(const MDL_KEY *mdl_key)
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@ -412,11 +412,11 @@ static void free_lock_object(MDL_LOCK *lock)
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/**
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Auxiliary functions needed for creation/destruction of MDL_LOCK_TICKET
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objects.
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Auxiliary functions needed for creation/destruction of MDL_LOCK_TICKET
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objects.
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@todo This naive implementation should be replaced with one that saves
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on memory allocation by reusing released objects.
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@todo This naive implementation should be replaced with one that saves
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on memory allocation by reusing released objects.
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*/
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static MDL_LOCK_TICKET* alloc_ticket_object(MDL_CONTEXT *context)
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@ -433,7 +433,7 @@ static void free_ticket_object(MDL_LOCK_TICKET *ticket)
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/**
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Helper functions which simplifies writing various checks and asserts.
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Helper functions which simplifies writing various checks and asserts.
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*/
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template <typename T>
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@ -444,16 +444,16 @@ static inline bool is_shared(T *lock_data)
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/**
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Helper functions and macros to be used for killable waiting in metadata
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locking subsystem.
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Helper functions and macros to be used for killable waiting in metadata
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locking subsystem.
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@sa THD::enter_cond()/exit_cond()/killed.
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@sa THD::enter_cond()/exit_cond()/killed.
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@note We can't use THD::enter_cond()/exit_cond()/killed directly here
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since this will make metadata subsystem dependant on THD class
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and thus prevent us from writing unit tests for it. And usage of
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wrapper functions to access THD::killed/enter_cond()/exit_cond()
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will probably introduce too much overhead.
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@note We can't use THD::enter_cond()/exit_cond()/killed directly here
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since this will make metadata subsystem dependant on THD class
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and thus prevent us from writing unit tests for it. And usage of
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wrapper functions to access THD::killed/enter_cond()/exit_cond()
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will probably introduce too much overhead.
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*/
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#define MDL_ENTER_COND(A, B) mdl_enter_cond(A, B, __func__, __FILE__, __LINE__)
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@ -496,41 +496,41 @@ static inline void mdl_exit_cond(MDL_CONTEXT *context,
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/**
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Check if request for the lock on particular object can be satisfied given
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current state of the global metadata lock.
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Check if request for the lock on particular object can be satisfied given
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current state of the global metadata lock.
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@note In other words, we're trying to check that the individual lock
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request, implying a form of lock on the global metadata, is
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compatible with the current state of the global metadata lock.
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@note In other words, we're trying to check that the individual lock
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request, implying a form of lock on the global metadata, is
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compatible with the current state of the global metadata lock.
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@param lock_req Request for lock on an individual object, implying a
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certain kind of global metadata lock.
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@param lock_req Request for lock on an individual object, implying a
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certain kind of global metadata lock.
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@retval TRUE - Lock request can be satisfied
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@retval FALSE - There is some conflicting lock
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@retval TRUE - Lock request can be satisfied
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@retval FALSE - There is some conflicting lock
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Here is a compatibility matrix defined by this function:
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Here is a compatibility matrix defined by this function:
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| | Satisfied or pending requests
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| | for global metadata lock
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----------------+-------------+--------------------------------------------
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Type of request | Correspond. |
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for indiv. lock | global lock | Active-S Pending-S Active-IS(**) Active-IX
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----------------+-------------+--------------------------------------------
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S, high-prio S | IS | + + + +
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upgradable S | IX | - - + +
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X | IX | - - + +
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S upgraded to X | IX (*) | 0 + + +
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| | Satisfied or pending requests
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| | for global metadata lock
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----------------+-------------+--------------------------------------------
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Type of request | Correspond. |
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for indiv. lock | global lock | Active-S Pending-S Active-IS(**) Active-IX
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----------------+-------------+--------------------------------------------
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S, high-prio S | IS | + + + +
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upgradable S | IX | - - + +
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X | IX | - - + +
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S upgraded to X | IX (*) | 0 + + +
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Here: "+" -- means that request can be satisfied
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"-" -- means that request can't be satisfied and should wait
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"0" -- means impossible situation which will trigger assert
|
||||
Here: "+" -- means that request can be satisfied
|
||||
"-" -- means that request can't be satisfied and should wait
|
||||
"0" -- means impossible situation which will trigger assert
|
||||
|
||||
(*) Since for upgradable shared locks we always take intention exclusive
|
||||
global lock at the same time when obtaining the shared lock, there
|
||||
is no need to obtain such lock during the upgrade itself.
|
||||
(**) Since intention shared global locks are compatible with all other
|
||||
type of locks we don't even have any accounting for them.
|
||||
(*) Since for upgradable shared locks we always take intention exclusive
|
||||
global lock at the same time when obtaining the shared lock, there
|
||||
is no need to obtain such lock during the upgrade itself.
|
||||
(**) Since intention shared global locks are compatible with all other
|
||||
type of locks we don't even have any accounting for them.
|
||||
*/
|
||||
|
||||
static bool can_grant_global_lock(enum_mdl_type type, bool is_upgrade)
|
||||
|
|
@ -588,33 +588,33 @@ static bool can_grant_global_lock(enum_mdl_type type, bool is_upgrade)
|
|||
|
||||
|
||||
/**
|
||||
Check if request for the lock can be satisfied given current state of lock.
|
||||
Check if request for the lock can be satisfied given current state of lock.
|
||||
|
||||
@param lock Lock.
|
||||
@param lock_req Request for lock.
|
||||
@param lock Lock.
|
||||
@param lock_req Request for lock.
|
||||
|
||||
@retval TRUE Lock request can be satisfied
|
||||
@retval FALSE There is some conflicting lock.
|
||||
@retval TRUE Lock request can be satisfied
|
||||
@retval FALSE There is some conflicting lock.
|
||||
|
||||
This function defines the following compatibility matrix for metadata locks:
|
||||
This function defines the following compatibility matrix for metadata locks:
|
||||
|
||||
| Satisfied or pending requests which we have in MDL_LOCK
|
||||
----------------+---------------------------------------------------------
|
||||
Current request | Active-S Pending-X Active-X Act-S-pend-upgrade-to-X
|
||||
----------------+---------------------------------------------------------
|
||||
S, upgradable S | + - - (*) -
|
||||
High-prio S | + + - +
|
||||
X | - + - -
|
||||
S upgraded to X | - (**) + 0 0
|
||||
| Satisfied or pending requests which we have in MDL_LOCK
|
||||
----------------+---------------------------------------------------------
|
||||
Current request | Active-S Pending-X Active-X Act-S-pend-upgrade-to-X
|
||||
----------------+---------------------------------------------------------
|
||||
S, upgradable S | + - - (*) -
|
||||
High-prio S | + + - +
|
||||
X | - + - -
|
||||
S upgraded to X | - (**) + 0 0
|
||||
|
||||
Here: "+" -- means that request can be satisfied
|
||||
"-" -- means that request can't be satisfied and should wait
|
||||
"0" -- means impossible situation which will trigger assert
|
||||
Here: "+" -- means that request can be satisfied
|
||||
"-" -- means that request can't be satisfied and should wait
|
||||
"0" -- means impossible situation which will trigger assert
|
||||
|
||||
(*) Unless active exclusive lock belongs to the same context as shared
|
||||
lock being requested.
|
||||
(**) Unless all active shared locks belong to the same context as one
|
||||
being upgraded.
|
||||
(*) Unless active exclusive lock belongs to the same context as shared
|
||||
lock being requested.
|
||||
(**) Unless all active shared locks belong to the same context as one
|
||||
being upgraded.
|
||||
*/
|
||||
|
||||
static bool can_grant_lock(MDL_CONTEXT *ctx, MDL_LOCK *lock,
|
||||
|
|
@ -683,12 +683,12 @@ static bool can_grant_lock(MDL_CONTEXT *ctx, MDL_LOCK *lock,
|
|||
|
||||
|
||||
/**
|
||||
Check whether the context already holds a compatible lock ticket
|
||||
on a object. Only shared locks can be recursive.
|
||||
Check whether the context already holds a compatible lock ticket
|
||||
on a object. Only shared locks can be recursive.
|
||||
|
||||
@param lock_req Lock request object for lock to be acquired
|
||||
@param lock_req Lock request object for lock to be acquired
|
||||
|
||||
@return A pointer to the lock ticket for the object or NULL otherwise.
|
||||
@return A pointer to the lock ticket for the object or NULL otherwise.
|
||||
*/
|
||||
|
||||
static MDL_LOCK_TICKET *
|
||||
|
|
@ -711,28 +711,28 @@ mdl_context_find_ticket(MDL_CONTEXT *ctx, MDL_LOCK_REQUEST *lock_req)
|
|||
|
||||
|
||||
/**
|
||||
Try to acquire one shared lock.
|
||||
Try to acquire one shared lock.
|
||||
|
||||
Unlike exclusive locks, shared locks are acquired one by
|
||||
one. This is interface is chosen to simplify introduction of
|
||||
the new locking API to the system. mdl_acquire_shared_lock()
|
||||
is currently used from open_table(), and there we have only one
|
||||
table to work with.
|
||||
Unlike exclusive locks, shared locks are acquired one by
|
||||
one. This is interface is chosen to simplify introduction of
|
||||
the new locking API to the system. mdl_acquire_shared_lock()
|
||||
is currently used from open_table(), and there we have only one
|
||||
table to work with.
|
||||
|
||||
In future we may consider allocating multiple shared locks at once.
|
||||
In future we may consider allocating multiple shared locks at once.
|
||||
|
||||
This function must be called after the lock is added to a context.
|
||||
This function must be called after the lock is added to a context.
|
||||
|
||||
@param context [in] Context containing request for lock
|
||||
@param lock_req [in] Lock request object for lock to be acquired
|
||||
@param retry [out] Indicates that conflicting lock exists and another
|
||||
attempt should be made after releasing all current
|
||||
locks and waiting for conflicting lock go away
|
||||
(using mdl_wait_for_locks()).
|
||||
@param context [in] Context containing request for lock
|
||||
@param lock_req [in] Lock request object for lock to be acquired
|
||||
@param retry [out] Indicates that conflicting lock exists and another
|
||||
attempt should be made after releasing all current
|
||||
locks and waiting for conflicting lock go away
|
||||
(using mdl_wait_for_locks()).
|
||||
|
||||
@retval FALSE Success.
|
||||
@retval TRUE Failure. Either error occured or conflicting lock exists.
|
||||
In the latter case "retry" parameter is set to TRUE.
|
||||
@retval FALSE Success.
|
||||
@retval TRUE Failure. Either error occured or conflicting lock exists.
|
||||
In the latter case "retry" parameter is set to TRUE.
|
||||
*/
|
||||
|
||||
bool mdl_acquire_shared_lock(MDL_CONTEXT *context, MDL_LOCK_REQUEST *lock_req,
|
||||
|
|
@ -824,13 +824,13 @@ static void release_ticket(MDL_CONTEXT *context, MDL_LOCK_TICKET *ticket);
|
|||
|
||||
|
||||
/**
|
||||
Notify a thread holding a shared metadata lock of a pending exclusive lock.
|
||||
Notify a thread holding a shared metadata lock of a pending exclusive lock.
|
||||
|
||||
@param thd Current thread context
|
||||
@param conf_lock_ticket Conflicting metadata lock
|
||||
@param thd Current thread context
|
||||
@param conf_lock_ticket Conflicting metadata lock
|
||||
|
||||
@retval TRUE A thread was woken up
|
||||
@retval FALSE Lock is not a shared one or no thread was woken up
|
||||
@retval TRUE A thread was woken up
|
||||
@retval FALSE Lock is not a shared one or no thread was woken up
|
||||
*/
|
||||
|
||||
static bool notify_shared_lock(THD *thd, MDL_LOCK_TICKET *conf_lock_ticket)
|
||||
|
|
@ -843,18 +843,18 @@ static bool notify_shared_lock(THD *thd, MDL_LOCK_TICKET *conf_lock_ticket)
|
|||
|
||||
|
||||
/**
|
||||
Acquire exclusive locks. The context must contain the list of
|
||||
locks to be acquired. There must be no granted locks in the
|
||||
context.
|
||||
Acquire exclusive locks. The context must contain the list of
|
||||
locks to be acquired. There must be no granted locks in the
|
||||
context.
|
||||
|
||||
This is a replacement of lock_table_names(). It is used in
|
||||
RENAME, DROP and other DDL SQL statements.
|
||||
This is a replacement of lock_table_names(). It is used in
|
||||
RENAME, DROP and other DDL SQL statements.
|
||||
|
||||
@param context A context containing requests for exclusive locks
|
||||
The context may not have other lock requests.
|
||||
@param context A context containing requests for exclusive locks
|
||||
The context may not have other lock requests.
|
||||
|
||||
@retval FALSE Success
|
||||
@retval TRUE Failure
|
||||
@retval FALSE Success
|
||||
@retval TRUE Failure
|
||||
*/
|
||||
|
||||
bool mdl_acquire_exclusive_locks(MDL_CONTEXT *context)
|
||||
|
|
@ -1009,25 +1009,25 @@ err:
|
|||
|
||||
|
||||
/**
|
||||
Upgrade a shared metadata lock to exclusive.
|
||||
Upgrade a shared metadata lock to exclusive.
|
||||
|
||||
Used in ALTER TABLE, when a copy of the table with the
|
||||
new definition has been constructed.
|
||||
Used in ALTER TABLE, when a copy of the table with the
|
||||
new definition has been constructed.
|
||||
|
||||
@param context Context to which shared lock belongs
|
||||
@param ticket Ticket for shared lock to be upgraded
|
||||
@param context Context to which shared lock belongs
|
||||
@param ticket Ticket for shared lock to be upgraded
|
||||
|
||||
@note In case of failure to upgrade lock (e.g. because upgrader
|
||||
was killed) leaves lock in its original state (locked in
|
||||
shared mode).
|
||||
@note In case of failure to upgrade lock (e.g. because upgrader
|
||||
was killed) leaves lock in its original state (locked in
|
||||
shared mode).
|
||||
|
||||
@note There can be only one upgrader for a lock or we will have deadlock.
|
||||
This invariant is ensured by code outside of metadata subsystem usually
|
||||
by obtaining some sort of exclusive table-level lock (e.g. TL_WRITE,
|
||||
TL_WRITE_ALLOW_READ) before performing upgrade of metadata lock.
|
||||
@note There can be only one upgrader for a lock or we will have deadlock.
|
||||
This invariant is ensured by code outside of metadata subsystem usually
|
||||
by obtaining some sort of exclusive table-level lock (e.g. TL_WRITE,
|
||||
TL_WRITE_ALLOW_READ) before performing upgrade of metadata lock.
|
||||
|
||||
@retval FALSE Success
|
||||
@retval TRUE Failure (thread was killed)
|
||||
@retval FALSE Success
|
||||
@retval TRUE Failure (thread was killed)
|
||||
*/
|
||||
|
||||
bool mdl_upgrade_shared_lock_to_exclusive(MDL_CONTEXT *context,
|
||||
|
|
@ -1110,27 +1110,27 @@ bool mdl_upgrade_shared_lock_to_exclusive(MDL_CONTEXT *context,
|
|||
|
||||
|
||||
/**
|
||||
Try to acquire an exclusive lock on the object if there are
|
||||
no conflicting locks.
|
||||
Try to acquire an exclusive lock on the object if there are
|
||||
no conflicting locks.
|
||||
|
||||
Similar to the previous function, but returns
|
||||
immediately without any side effect if encounters a lock
|
||||
conflict. Otherwise takes the lock.
|
||||
Similar to the previous function, but returns
|
||||
immediately without any side effect if encounters a lock
|
||||
conflict. Otherwise takes the lock.
|
||||
|
||||
This function is used in CREATE TABLE ... LIKE to acquire a lock
|
||||
on the table to be created. In this statement we don't want to
|
||||
block and wait for the lock if the table already exists.
|
||||
This function is used in CREATE TABLE ... LIKE to acquire a lock
|
||||
on the table to be created. In this statement we don't want to
|
||||
block and wait for the lock if the table already exists.
|
||||
|
||||
@param context [in] The context containing the lock request
|
||||
@param lock_req [in] The lock request
|
||||
@param conflict [out] Indicates that conflicting lock exists
|
||||
@param context [in] The context containing the lock request
|
||||
@param lock_req [in] The lock request
|
||||
@param conflict [out] Indicates that conflicting lock exists
|
||||
|
||||
@retval TRUE Failure either conflicting lock exists or some error
|
||||
occured (probably OOM).
|
||||
@retval FALSE Success, lock was acquired.
|
||||
@retval TRUE Failure either conflicting lock exists or some error
|
||||
occured (probably OOM).
|
||||
@retval FALSE Success, lock was acquired.
|
||||
|
||||
FIXME: Compared to lock_table_name_if_not_cached()
|
||||
it gives sligthly more false negatives.
|
||||
FIXME: Compared to lock_table_name_if_not_cached()
|
||||
it gives sligthly more false negatives.
|
||||
*/
|
||||
|
||||
bool mdl_try_acquire_exclusive_lock(MDL_CONTEXT *context,
|
||||
|
|
@ -1184,15 +1184,15 @@ err:
|
|||
|
||||
|
||||
/**
|
||||
Acquire global shared metadata lock.
|
||||
Acquire global shared metadata lock.
|
||||
|
||||
Holding this lock will block all requests for exclusive locks
|
||||
and shared locks which can be potentially upgraded to exclusive.
|
||||
Holding this lock will block all requests for exclusive locks
|
||||
and shared locks which can be potentially upgraded to exclusive.
|
||||
|
||||
@param context Current metadata locking context.
|
||||
@param context Current metadata locking context.
|
||||
|
||||
@retval FALSE Success -- the lock was granted.
|
||||
@retval TRUE Failure -- our thread was killed.
|
||||
@retval FALSE Success -- the lock was granted.
|
||||
@retval TRUE Failure -- our thread was killed.
|
||||
*/
|
||||
|
||||
bool mdl_acquire_global_shared_lock(MDL_CONTEXT *context)
|
||||
|
|
@ -1227,18 +1227,18 @@ bool mdl_acquire_global_shared_lock(MDL_CONTEXT *context)
|
|||
|
||||
|
||||
/**
|
||||
Wait until there will be no locks that conflict with lock requests
|
||||
in the context.
|
||||
Wait until there will be no locks that conflict with lock requests
|
||||
in the context.
|
||||
|
||||
This is a part of the locking protocol and must be used by the
|
||||
acquirer of shared locks after a back-off.
|
||||
This is a part of the locking protocol and must be used by the
|
||||
acquirer of shared locks after a back-off.
|
||||
|
||||
Does not acquire the locks!
|
||||
Does not acquire the locks!
|
||||
|
||||
@param context Context with which lock requests are associated.
|
||||
@param context Context with which lock requests are associated.
|
||||
|
||||
@retval FALSE Success. One can try to obtain metadata locks.
|
||||
@retval TRUE Failure (thread was killed)
|
||||
@retval FALSE Success. One can try to obtain metadata locks.
|
||||
@retval TRUE Failure (thread was killed)
|
||||
*/
|
||||
|
||||
bool mdl_wait_for_locks(MDL_CONTEXT *context)
|
||||
|
|
@ -1297,8 +1297,8 @@ bool mdl_wait_for_locks(MDL_CONTEXT *context)
|
|||
|
||||
|
||||
/**
|
||||
Auxiliary function which allows to release particular lock
|
||||
ownership of which is represented by a lock ticket object.
|
||||
Auxiliary function which allows to release particular lock
|
||||
ownership of which is represented by a lock ticket object.
|
||||
*/
|
||||
|
||||
static void release_ticket(MDL_CONTEXT *context, MDL_LOCK_TICKET *ticket)
|
||||
|
|
@ -1347,15 +1347,15 @@ static void release_ticket(MDL_CONTEXT *context, MDL_LOCK_TICKET *ticket)
|
|||
|
||||
|
||||
/**
|
||||
Release all locks associated with the context, but leave them
|
||||
in the context as lock requests.
|
||||
Release all locks associated with the context, but leave them
|
||||
in the context as lock requests.
|
||||
|
||||
This function is used to back off in case of a lock conflict.
|
||||
It is also used to release shared locks in the end of an SQL
|
||||
statement.
|
||||
This function is used to back off in case of a lock conflict.
|
||||
It is also used to release shared locks in the end of an SQL
|
||||
statement.
|
||||
|
||||
@param context The context with which the locks to be released
|
||||
are associated.
|
||||
@param context The context with which the locks to be released
|
||||
are associated.
|
||||
*/
|
||||
|
||||
void mdl_ticket_release_all(MDL_CONTEXT *context)
|
||||
|
|
@ -1395,11 +1395,10 @@ void mdl_ticket_release_all(MDL_CONTEXT *context)
|
|||
|
||||
|
||||
/**
|
||||
Release a lock.
|
||||
|
||||
@param context Context containing lock in question
|
||||
@param ticket Lock to be released
|
||||
Release a lock.
|
||||
|
||||
@param context Context containing lock in question
|
||||
@param ticket Lock to be released
|
||||
*/
|
||||
|
||||
void mdl_ticket_release(MDL_CONTEXT *context, MDL_LOCK_TICKET *ticket)
|
||||
|
|
@ -1415,12 +1414,12 @@ void mdl_ticket_release(MDL_CONTEXT *context, MDL_LOCK_TICKET *ticket)
|
|||
|
||||
|
||||
/**
|
||||
Release all locks in the context which correspond to the same name/
|
||||
object as this lock request, remove lock requests from the context.
|
||||
Release all locks in the context which correspond to the same name/
|
||||
object as this lock request, remove lock requests from the context.
|
||||
|
||||
@param context Context containing locks in question
|
||||
@param ticket One of the locks for the name/object for which all
|
||||
locks should be released.
|
||||
@param context Context containing locks in question
|
||||
@param ticket One of the locks for the name/object for which all
|
||||
locks should be released.
|
||||
*/
|
||||
|
||||
void mdl_ticket_release_all_for_name(MDL_CONTEXT *context,
|
||||
|
|
@ -1461,10 +1460,10 @@ void mdl_ticket_release_all_for_name(MDL_CONTEXT *context,
|
|||
|
||||
|
||||
/**
|
||||
Downgrade an exclusive lock to shared metadata lock.
|
||||
Downgrade an exclusive lock to shared metadata lock.
|
||||
|
||||
@param context A context to which exclusive lock belongs
|
||||
@param ticket Ticket for exclusive lock to be downgraded
|
||||
@param context A context to which exclusive lock belongs
|
||||
@param ticket Ticket for exclusive lock to be downgraded
|
||||
*/
|
||||
|
||||
void mdl_downgrade_exclusive_lock(MDL_CONTEXT *context,
|
||||
|
|
@ -1490,9 +1489,9 @@ void mdl_downgrade_exclusive_lock(MDL_CONTEXT *context,
|
|||
|
||||
|
||||
/**
|
||||
Release global shared metadata lock.
|
||||
Release global shared metadata lock.
|
||||
|
||||
@param context Current context
|
||||
@param context Current context
|
||||
*/
|
||||
|
||||
void mdl_release_global_shared_lock(MDL_CONTEXT *context)
|
||||
|
|
@ -1509,16 +1508,16 @@ void mdl_release_global_shared_lock(MDL_CONTEXT *context)
|
|||
|
||||
|
||||
/**
|
||||
Auxiliary function which allows to check if we have exclusive lock
|
||||
on the object.
|
||||
Auxiliary function which allows to check if we have exclusive lock
|
||||
on the object.
|
||||
|
||||
@param context Current context
|
||||
@param type Id of object type
|
||||
@param db Name of the database
|
||||
@param name Name of the object
|
||||
@param context Current context
|
||||
@param type Id of object type
|
||||
@param db Name of the database
|
||||
@param name Name of the object
|
||||
|
||||
@return TRUE if current context contains exclusive lock for the object,
|
||||
FALSE otherwise.
|
||||
@return TRUE if current context contains exclusive lock for the object,
|
||||
FALSE otherwise.
|
||||
*/
|
||||
|
||||
bool mdl_is_exclusive_lock_owner(MDL_CONTEXT *context, unsigned char type,
|
||||
|
|
@ -1542,16 +1541,16 @@ bool mdl_is_exclusive_lock_owner(MDL_CONTEXT *context, unsigned char type,
|
|||
|
||||
|
||||
/**
|
||||
Auxiliary function which allows to check if we have some kind of lock on
|
||||
a object.
|
||||
Auxiliary function which allows to check if we have some kind of lock on
|
||||
a object.
|
||||
|
||||
@param context Current context
|
||||
@param type Id of object type
|
||||
@param db Name of the database
|
||||
@param name Name of the object
|
||||
@param context Current context
|
||||
@param type Id of object type
|
||||
@param db Name of the database
|
||||
@param name Name of the object
|
||||
|
||||
@return TRUE if current context contains satisfied lock for the object,
|
||||
FALSE otherwise.
|
||||
@return TRUE if current context contains satisfied lock for the object,
|
||||
FALSE otherwise.
|
||||
*/
|
||||
|
||||
bool mdl_is_lock_owner(MDL_CONTEXT *context, unsigned char type,
|
||||
|
|
@ -1574,12 +1573,12 @@ bool mdl_is_lock_owner(MDL_CONTEXT *context, unsigned char type,
|
|||
|
||||
|
||||
/**
|
||||
Check if we have any pending exclusive locks which conflict with
|
||||
existing shared lock.
|
||||
Check if we have any pending exclusive locks which conflict with
|
||||
existing shared lock.
|
||||
|
||||
@param ticket Shared lock against which check should be performed.
|
||||
@param ticket Shared lock against which check should be performed.
|
||||
|
||||
@return TRUE if there are any conflicting locks, FALSE otherwise.
|
||||
@return TRUE if there are any conflicting locks, FALSE otherwise.
|
||||
*/
|
||||
|
||||
bool mdl_has_pending_conflicting_lock(MDL_LOCK_TICKET *ticket)
|
||||
|
|
@ -1597,31 +1596,31 @@ bool mdl_has_pending_conflicting_lock(MDL_LOCK_TICKET *ticket)
|
|||
|
||||
|
||||
/**
|
||||
Associate pointer to an opaque object with a lock.
|
||||
Associate pointer to an opaque object with a lock.
|
||||
|
||||
@param ticket Lock ticket for the lock with which the object
|
||||
should be associated.
|
||||
@param cached_object Pointer to the object
|
||||
@param release_hook Cleanup function to be called when MDL subsystem
|
||||
decides to remove lock or associate another object.
|
||||
@param ticket Lock ticket for the lock with which the object
|
||||
should be associated.
|
||||
@param cached_object Pointer to the object
|
||||
@param release_hook Cleanup function to be called when MDL subsystem
|
||||
decides to remove lock or associate another object.
|
||||
|
||||
This is used to cache a pointer to TABLE_SHARE in the lock
|
||||
structure. Such caching can save one acquisition of LOCK_open
|
||||
and one table definition cache lookup for every table.
|
||||
This is used to cache a pointer to TABLE_SHARE in the lock
|
||||
structure. Such caching can save one acquisition of LOCK_open
|
||||
and one table definition cache lookup for every table.
|
||||
|
||||
Since the pointer may be stored only inside an acquired lock,
|
||||
the caching is only effective when there is more than one lock
|
||||
granted on a given table.
|
||||
Since the pointer may be stored only inside an acquired lock,
|
||||
the caching is only effective when there is more than one lock
|
||||
granted on a given table.
|
||||
|
||||
This function has the following usage pattern:
|
||||
- try to acquire an MDL lock
|
||||
- when done, call for mdl_get_cached_object(). If it returns NULL, our
|
||||
thread has the only lock on this table.
|
||||
- look up TABLE_SHARE in the table definition cache
|
||||
- call mdl_set_cache_object() to assign the share to the opaque pointer.
|
||||
This function has the following usage pattern:
|
||||
- try to acquire an MDL lock
|
||||
- when done, call for mdl_get_cached_object(). If it returns NULL, our
|
||||
thread has the only lock on this table.
|
||||
- look up TABLE_SHARE in the table definition cache
|
||||
- call mdl_set_cache_object() to assign the share to the opaque pointer.
|
||||
|
||||
The release hook is invoked when the last shared metadata
|
||||
lock on this name is released.
|
||||
The release hook is invoked when the last shared metadata
|
||||
lock on this name is released.
|
||||
*/
|
||||
|
||||
void mdl_set_cached_object(MDL_LOCK_TICKET *ticket, void *cached_object,
|
||||
|
|
@ -1648,11 +1647,11 @@ void mdl_set_cached_object(MDL_LOCK_TICKET *ticket, void *cached_object,
|
|||
|
||||
|
||||
/**
|
||||
Get a pointer to an opaque object that associated with the lock.
|
||||
Get a pointer to an opaque object that associated with the lock.
|
||||
|
||||
@param ticket Lock ticket for the lock which the object is associated to.
|
||||
@param ticket Lock ticket for the lock which the object is associated to.
|
||||
|
||||
@return Pointer to an opaque object associated with the lock.
|
||||
@return Pointer to an opaque object associated with the lock.
|
||||
*/
|
||||
|
||||
void* mdl_get_cached_object(MDL_LOCK_TICKET *ticket)
|
||||
|
|
|
|||
62
sql/mdl.h
62
sql/mdl.h
|
|
@ -29,15 +29,15 @@ struct MDL_LOCK;
|
|||
struct MDL_CONTEXT;
|
||||
|
||||
/**
|
||||
Type of metadata lock request.
|
||||
Type of metadata lock request.
|
||||
|
||||
- High-priority shared locks differ from ordinary shared locks by
|
||||
that they ignore pending requests for exclusive locks.
|
||||
- Upgradable shared locks can be later upgraded to exclusive
|
||||
(because of that their acquisition involves implicit
|
||||
acquisition of global intention-exclusive lock).
|
||||
- High-priority shared locks differ from ordinary shared locks by
|
||||
that they ignore pending requests for exclusive locks.
|
||||
- Upgradable shared locks can be later upgraded to exclusive
|
||||
(because of that their acquisition involves implicit
|
||||
acquisition of global intention-exclusive lock).
|
||||
|
||||
@see Comments for can_grant_lock() and can_grant_global_lock() for details.
|
||||
@see Comments for can_grant_lock() and can_grant_global_lock() for details.
|
||||
*/
|
||||
|
||||
enum enum_mdl_type {MDL_SHARED=0, MDL_SHARED_HIGH_PRIO,
|
||||
|
|
@ -54,12 +54,12 @@ enum enum_mdl_state { MDL_PENDING, MDL_ACQUIRED };
|
|||
|
||||
|
||||
/**
|
||||
Metadata lock object key.
|
||||
Metadata lock object key.
|
||||
|
||||
A lock is requested or granted based on a fully qualified name and type.
|
||||
E.g. They key for a table consists of <0 (=table)>+<database>+<table name>.
|
||||
Elsewhere in the comments this triple will be referred to simply as "key"
|
||||
or "name".
|
||||
A lock is requested or granted based on a fully qualified name and type.
|
||||
E.g. They key for a table consists of <0 (=table)>+<database>+<table name>.
|
||||
Elsewhere in the comments this triple will be referred to simply as "key"
|
||||
or "name".
|
||||
*/
|
||||
|
||||
class MDL_KEY
|
||||
|
|
@ -110,8 +110,8 @@ private:
|
|||
|
||||
|
||||
/**
|
||||
Hook class which via its methods specifies which members
|
||||
of T should be used for participating in MDL lists.
|
||||
Hook class which via its methods specifies which members
|
||||
of T should be used for participating in MDL lists.
|
||||
*/
|
||||
|
||||
template <typename T, T* T::*next, T** T::*prev>
|
||||
|
|
@ -124,12 +124,12 @@ struct I_P_List_adapter
|
|||
|
||||
|
||||
/**
|
||||
A pending metadata lock request.
|
||||
A pending lock request or a granted metadata lock share the same abstract
|
||||
base but are presented individually because they have different allocation
|
||||
sites and hence different lifetimes. The allocation of lock requests is
|
||||
controlled from outside of the MDL subsystem, while allocation of granted
|
||||
locks (tickets) is controlled within the MDL subsystem.
|
||||
A pending metadata lock request.
|
||||
A pending lock request or a granted metadata lock share the same abstract
|
||||
base but are presented individually because they have different allocation
|
||||
sites and hence different lifetimes. The allocation of lock requests is
|
||||
controlled from outside of the MDL subsystem, while allocation of granted
|
||||
locks (tickets) is controlled within the MDL subsystem.
|
||||
*/
|
||||
|
||||
struct MDL_LOCK_REQUEST
|
||||
|
|
@ -138,7 +138,7 @@ struct MDL_LOCK_REQUEST
|
|||
enum enum_mdl_type type;
|
||||
|
||||
/**
|
||||
Pointers for participating in the list of lock requests for this context.
|
||||
Pointers for participating in the list of lock requests for this context.
|
||||
*/
|
||||
MDL_LOCK_REQUEST *next_in_context;
|
||||
MDL_LOCK_REQUEST **prev_in_context;
|
||||
|
|
@ -154,12 +154,12 @@ struct MDL_LOCK_REQUEST
|
|||
|
||||
|
||||
/**
|
||||
A granted metadata lock.
|
||||
A granted metadata lock.
|
||||
|
||||
@warning MDL_LOCK_TICKET members are private to the MDL subsystem.
|
||||
@warning MDL_LOCK_TICKET members are private to the MDL subsystem.
|
||||
|
||||
@note Multiple shared locks on a same object are represented by a
|
||||
single ticket. The same does not apply for other lock types.
|
||||
@note Multiple shared locks on a same object are represented by a
|
||||
single ticket. The same does not apply for other lock types.
|
||||
*/
|
||||
|
||||
struct MDL_LOCK_TICKET
|
||||
|
|
@ -170,13 +170,13 @@ struct MDL_LOCK_TICKET
|
|||
enum enum_mdl_state state;
|
||||
|
||||
/**
|
||||
Pointers for participating in the list of lock requests for this context.
|
||||
Pointers for participating in the list of lock requests for this context.
|
||||
*/
|
||||
MDL_LOCK_TICKET *next_in_context;
|
||||
MDL_LOCK_TICKET **prev_in_context;
|
||||
/**
|
||||
Pointers for participating in the list of satisfied/pending requests
|
||||
for the lock.
|
||||
Pointers for participating in the list of satisfied/pending requests
|
||||
for the lock.
|
||||
*/
|
||||
MDL_LOCK_TICKET *next_in_lock;
|
||||
MDL_LOCK_TICKET **prev_in_lock;
|
||||
|
|
@ -189,8 +189,8 @@ struct MDL_LOCK_TICKET
|
|||
|
||||
|
||||
/**
|
||||
Context of the owner of metadata locks. I.e. each server
|
||||
connection has such a context.
|
||||
Context of the owner of metadata locks. I.e. each server
|
||||
connection has such a context.
|
||||
*/
|
||||
|
||||
struct MDL_CONTEXT
|
||||
|
|
@ -286,7 +286,7 @@ void mdl_rollback_to_savepoint(MDL_CONTEXT *ctx,
|
|||
MDL_LOCK_TICKET *mdl_savepoint);
|
||||
|
||||
/**
|
||||
Get iterator for walking through all lock requests in the context.
|
||||
Get iterator for walking through all lock requests in the context.
|
||||
*/
|
||||
|
||||
inline MDL_CONTEXT::Request_iterator
|
||||
|
|
|
|||
Loading…
Add table
Reference in a new issue