30 commits

Author	SHA1	Message	Date
Christopher Powers	8f3d884dd2	Bug#35333, "If Federated table can't connect to remote host, can't retrieve ... metadata" Improved error handling such that queries against Information_Schema.Tables won't fail if a federated table can't make a remote connection. mysql-test/r/lock_multi.result: Updated with warnings that were previously masked. mysql-test/r/mdl_sync.result: Updated with warnings that were previously masked. mysql-test/r/merge.result: Updated with warnings that were previously masked. mysql-test/r/show_check.result: Updated with warnings that were previously masked. mysql-test/r/view.result: Updated with warnings that were previously masked. mysql-test/suite/federated/federated_bug_35333.result: New test results for bug#35333 mysql-test/suite/federated/federated_bug_35333.test: New test or bug#35333 sql/sql_show.cc: If get_schema_tables_record() encounters an error, push a warning, set the TABLE COMMENT column with the error text, and clear the error so that the operation can continue.	2010-11-30 11:20:56 -06:00
Dmitry Lenev	6bf6272fda	Patch that refactors global read lock implementation and fixes ... bug #57006 "Deadlock between HANDLER and FLUSH TABLES WITH READ LOCK" and bug #54673 "It takes too long to get readlock for 'FLUSH TABLES WITH READ LOCK'". The first bug manifested itself as a deadlock which occurred when a connection, which had some table open through HANDLER statement, tried to update some data through DML statement while another connection tried to execute FLUSH TABLES WITH READ LOCK concurrently. What happened was that FTWRL in the second connection managed to perform first step of GRL acquisition and thus blocked all upcoming DML. After that it started to wait for table open through HANDLER statement to be flushed. When the first connection tried to execute DML it has started to wait for GRL/the second connection creating deadlock. The second bug manifested itself as starvation of FLUSH TABLES WITH READ LOCK statements in cases when there was a constant stream of concurrent DML statements (in two or more connections). This has happened because requests for protection against GRL which were acquired by DML statements were ignoring presence of pending GRL and thus the latter was starved. This patch solves both these problems by re-implementing GRL using metadata locks. Similar to the old implementation acquisition of GRL in new implementation is two-step. During the first step we block all concurrent DML and DDL statements by acquiring global S metadata lock (each DML and DDL statement acquires global IX lock for its duration). During the second step we block commits by acquiring global S lock in COMMIT namespace (commit code acquires global IX lock in this namespace). Note that unlike in old implementation acquisition of protection against GRL in DML and DDL is semi-automatic. We assume that any statement which should be blocked by GRL will either open and acquires write-lock on tables or acquires metadata locks on objects it is going to modify. For any such statement global IX metadata lock is automatically acquired for its duration. The first problem is solved because waits for GRL become visible to deadlock detector in metadata locking subsystem and thus deadlocks like one in the first bug become impossible. The second problem is solved because global S locks which are used for GRL implementation are given preference over IX locks which are acquired by concurrent DML (and we can switch to fair scheduling in future if needed). Important change: FTWRL/GRL no longer blocks DML and DDL on temporary tables. Before this patch behavior was not consistent in this respect: in some cases DML/DDL statements on temporary tables were blocked while in others they were not. Since the main use cases for FTWRL are various forms of backups and temporary tables are not preserved during backups we have opted for consistently allowing DML/DDL on temporary tables during FTWRL/GRL. Important change: This patch changes thread state names which are used when DML/DDL of FTWRL is waiting for global read lock. It is now either "Waiting for global read lock" or "Waiting for commit lock" depending on the stage on which FTWRL is. Incompatible change: To solve deadlock in events code which was exposed by this patch we have to replace LOCK_event_metadata mutex with metadata locks on events. As result we have to prohibit DDL on events under LOCK TABLES. This patch also adds extensive test coverage for interaction of DML/DDL and FTWRL. Performance of new and old global read lock implementations in sysbench tests were compared. There were no significant difference between new and old implementations. mysql-test/include/check_ftwrl_compatible.inc: Added helper script which allows to check that a statement is compatible with FLUSH TABLES WITH READ LOCK. mysql-test/include/check_ftwrl_incompatible.inc: Added helper script which allows to check that a statement is incompatible with FLUSH TABLES WITH READ LOCK. mysql-test/include/handler.inc: Adjusted test case to the fact that now DROP TABLE closes open HANDLERs for the table to be dropped before checking if there active FTWRL in this connection. mysql-test/include/wait_show_condition.inc: Fixed small error in the timeout message. The correct name of variable used as parameter for this script is "$condition" and not "$wait_condition". mysql-test/r/delayed.result: Added test coverage for scenario which triggered assert in metadata locking subsystem. mysql-test/r/events_2.result: Updated test results after prohibiting event DDL operations under LOCK TABLES. mysql-test/r/flush.result: Added test coverage for bug #57006 "Deadlock between HANDLER and FLUSH TABLES WITH READ LOCK". mysql-test/r/flush_read_lock.result: Added test coverage for various aspects of FLUSH TABLES WITH READ LOCK functionality. mysql-test/r/flush_read_lock_kill.result: Adjusted test case after replacing custom global read lock implementation with one based on metadata locks. Use new debug_sync point. Do not disable concurrent inserts as now InnoDB we always use InnoDB table. mysql-test/r/handler_innodb.result: Adjusted test case to the fact that now DROP TABLE closes open HANDLERs for the table to be dropped before checking if there active FTWRL in this connection. mysql-test/r/handler_myisam.result: Adjusted test case to the fact that now DROP TABLE closes open HANDLERs for the table to be dropped before checking if there active FTWRL in this connection. mysql-test/r/mdl_sync.result: Adjusted test case after replacing custom global read lock implementation with one based on metadata locks. Replaced usage of GRL-specific debug_sync's with appropriate sync points in MDL subsystem. mysql-test/suite/perfschema/r/dml_setup_instruments.result: Updated test results after removing global COND_global_read_lock condition variable. mysql-test/suite/perfschema/r/func_file_io.result: Ensure that this test doesn't affect subsequent tests. At the end of its execution enable back P_S instrumentation which this test disables at some point. mysql-test/suite/perfschema/r/func_mutex.result: Ensure that this test doesn't affect subsequent tests. At the end of its execution enable back P_S instrumentation which this test disables at some point. mysql-test/suite/perfschema/r/global_read_lock.result: Adjusted test case to take into account that new GRL implementation is based on MDL. mysql-test/suite/perfschema/r/server_init.result: Adjusted test case after replacing custom global read lock implementation with one based on MDL and replacing LOCK_event_metadata mutex with metadata lock. mysql-test/suite/perfschema/t/func_file_io.test: Ensure that this test doesn't affect subsequent tests. At the end of its execution enable back P_S instrumentation which this test disables at some point. mysql-test/suite/perfschema/t/func_mutex.test: Ensure that this test doesn't affect subsequent tests. At the end of its execution enable back P_S instrumentation which this test disables at some point. mysql-test/suite/perfschema/t/global_read_lock.test: Adjusted test case to take into account that new GRL implementation is based on MDL. mysql-test/suite/perfschema/t/server_init.test: Adjusted test case after replacing custom global read lock implementation with one based on MDL and replacing LOCK_event_metadata mutex with metadata lock. mysql-test/suite/rpl/r/rpl_tmp_table_and_DDL.result: Updated test results after prohibiting event DDL under LOCK TABLES. mysql-test/t/delayed.test: Added test coverage for scenario which triggered assert in metadata locking subsystem. mysql-test/t/events_2.test: Updated test case after prohibiting event DDL operations under LOCK TABLES. mysql-test/t/flush.test: Added test coverage for bug #57006 "Deadlock between HANDLER and FLUSH TABLES WITH READ LOCK". mysql-test/t/flush_block_commit.test: Adjusted test case after changing thread state name which is used when COMMIT waits for FLUSH TABLES WITH READ LOCK from "Waiting for release of readlock" to "Waiting for commit lock". mysql-test/t/flush_block_commit_notembedded.test: Adjusted test case after changing thread state name which is used when DML waits for FLUSH TABLES WITH READ LOCK. Now we use "Waiting for global read lock" in this case. mysql-test/t/flush_read_lock.test: Added test coverage for various aspects of FLUSH TABLES WITH READ LOCK functionality. mysql-test/t/flush_read_lock_kill-master.opt: We no longer need to use make_global_read_lock_block_commit_loop debug tag in this test. Instead we rely on an appropriate debug_sync point in MDL code. mysql-test/t/flush_read_lock_kill.test: Adjusted test case after replacing custom global read lock implementation with one based on metadata locks. Use new debug_sync point. Do not disable concurrent inserts as now InnoDB we always use InnoDB table. mysql-test/t/lock_multi.test: Adjusted test case after changing thread state names which are used when DML or DDL waits for FLUSH TABLES WITH READ LOCK to "Waiting for global read lock". mysql-test/t/mdl_sync.test: Adjusted test case after replacing custom global read lock implementation with one based on metadata locks. Replaced usage of GRL-specific debug_sync's with appropriate sync points in MDL subsystem. Updated thread state names which are used when DDL waits for FTWRL. mysql-test/t/trigger_notembedded.test: Adjusted test case after changing thread state names which are used when DML or DDL waits for FLUSH TABLES WITH READ LOCK to "Waiting for global read lock". sql/event_data_objects.cc: Removed Event_queue_element::status/last_executed_changed members and Event_queue_element::update_timing_fields() method. We no longer use this class for updating mysql.events once event is chosen for execution. Accesses to instances of this class in scheduler thread require protection by Event_queue::LOCK_event_queue mutex and we try to avoid updating table while holding this lock. sql/event_data_objects.h: Removed Event_queue_element::status/last_executed_changed members and Event_queue_element::update_timing_fields() method. We no longer use this class for updating mysql.events once event is chosen for execution. Accesses to instances of this class in scheduler thread require protection by Event_queue::LOCK_event_queue mutex and we try to avoid updating table while holding this lock. sql/event_db_repository.cc: - Changed Event_db_repository methods to not release all metadata locks once they are done updating mysql.events table. This allows to keep metadata lock protecting against GRL and lock protecting particular event around until corresponding DDL statement is written to the binary log. - Removed logic for conditional update of "status" and "last_executed" fields from update_timing_fields_for_event() method. In the only case when this method is called now "last_executed" is always modified and tracking change of "status" is too much hassle. sql/event_db_repository.h: Removed logic for conditional update of "status" and "last_executed" fields from Event_db_repository:: update_timing_fields_for_event() method. In the only case when this method is called now "last_executed" is always modified and tracking change of "status" field is too much hassle. sql/event_queue.cc: Changed event scheduler code not to update mysql.events table while holding Event_queue::LOCK_event_queue mutex. Doing so led to a deadlock with a new GRL implementation. This deadlock didn't occur with old implementation due to fact that code acquiring protection against GRL ignored pending GRL requests (which lead to GRL starvation). One of goals of new implementation is to disallow GRL starvation and so we have to solve problem with this deadlock in a different way. sql/events.cc: Changed methods of Events class to acquire protection against GRL while perfoming DDL statement and keep it until statement is written to the binary log. Unfortunately this step together with new GRL implementation exposed deadlock involving Events::LOCK_event_metadata and GRL. To solve it Events::LOCK_event_metadata mutex was replaced with a metadata lock on event. As a side-effect events DDL has to be prohibited under LOCK TABLES even in cases when mysql.events table was explicitly locked for write. sql/events.h: Replaced Events::LOCK_event_metadata mutex with a metadata lock on event. sql/ha_ndbcluster.cc: Updated code after replacing custom global read lock implementation with one based on MDL. Since MDL subsystem should now be able to detect deadlocks involving metadata locks and GRL there is no need for special handling of active GRL. sql/handler.cc: Replaced custom implementation of global read lock with one based on metadata locks. Consequently when doing commit instead of calling method of Global_read_lock class to acquire protection against GRL we simply acquire IX in COMMIT namespace. sql/lock.cc: Replaced custom implementation of global read lock with one based on metadata locks. This step allows to expose wait for GRL to deadlock detector of MDL subsystem and thus succesfully resolve deadlocks similar to one behind bug #57006 "Deadlock between HANDLER and FLUSH TABLES WITH READ LOCK". It also solves problem with GRL starvation described in bug #54673 "It takes too long to get readlock for 'FLUSH TABLES WITH READ LOCK'" since metadata locks used by GRL give preference to FTWRL statement instead of DML statements (if needed in future this can be changed to fair scheduling). Similar to old implementation of acquisition of GRL is two-step. During the first step we block all concurrent DML and DDL statements by acquiring global S metadata lock (each DML and DDL statement acquires global IX lock for its duration). During the second step we block commits by acquiring global S lock in COMMIT namespace (commit code acquires global IX lock in this namespace). Note that unlike in old implementation acquisition of protection against GRL in DML and DDL is semi-automatic. We assume that any statement which should be blocked by GRL will either open and acquires write-lock on tables or acquires metadata locks on objects it is going to modify. For any such statement global IX metadata lock is automatically acquired for its duration. To support this change: - Global_read_lock::lock/unlock_global_read_lock and make_global_read_lock_block_commit methods were changed accordingly. - Global_read_lock::wait_if_global_read_lock() and start_waiting_global_read_lock() methods were dropped. It is now responsibility of code acquiring metadata locks opening tables to acquire protection against GRL by explicitly taking global IX lock with statement duration. - Global variables, mutex and condition variable used by old implementation was removed. - lock_routine_name() was changed to use statement duration for its global IX lock. It was also renamed to lock_object_name() as it now also used to take metadata locks on events. - Global_read_lock::set_explicit_lock_duration() was added which allows not to release locks used for GRL when leaving prelocked mode. sql/lock.h: - Renamed lock_routine_name() to lock_object_name() and changed its signature to allow its usage for events. - Removed broadcast_refresh() function. It is no longer needed with new GRL implementation. sql/log_event.cc: Release metadata locks with statement duration at the end of processing legacy event for LOAD DATA. This ensures that replication thread processing such event properly releases its protection against global read lock. sql/mdl.cc: Changed MDL subsystem to support new MDL-based implementation of global read lock. Added COMMIT and EVENTS namespaces for metadata locks. Changed thread state name for GLOBAL namespace to "Waiting for global read lock". Optimized MDL_map::find_or_insert() method to avoid taking m_mutex mutex when looking up MDL_lock objects for GLOBAL or COMMIT namespaces. We keep pre-created MDL_lock objects for these namespaces around and simply return pointers to these global objects when needed. Changed MDL_lock/MDL_scoped_lock to properly handle notification of insert delayed handler threads when FTWRL takes global S lock. Introduced concept of lock duration. In addition to locks with transaction duration which work in the way which is similar to how locks worked before (i.e. they are released at the end of transaction), locks with statement and explicit duration were introduced. Locks with statement duration are automatically released at the end of statement. Locks with explicit duration require explicit release and obsolete concept of transactional sentinel. * Changed MDL_request and MDL_ticket classes to support notion of duration. * Changed MDL_context to keep locks with different duration in different lists. Changed code handling ticket list to take this into account. * Changed methods responsible for releasing locks to take into account duration of tickets. Particularly public MDL_context::release_lock() method now only can release tickets with explicit duration (there is still internal method which allows to specify duration). To release locks with statement or transaction duration one have to use release_statement/transactional_locks() methods. * Concept of savepoint for MDL subsystem now has to take into account locks with statement duration. Consequently MDL_savepoint class was introduced and methods working with savepoints were updated accordingly. * Added methods which allow to set duration for one or all locks in the context. sql/mdl.h: Changed MDL subsystem to support new MDL-based implementation of global read lock. Added COMMIT and EVENTS namespaces for metadata locks. Introduced concept of lock duration. In addition to locks with transaction duration which work in the way which is similar to how locks worked before (i.e. they are released at the end of transaction), locks with statement and explicit duration were introduced. Locks with statement duration are automatically released at the end of statement. Locks with explicit duration require explicit release and obsolete concept of transactional sentinel. * Changed MDL_request and MDL_ticket classes to support notion of duration. * Changed MDL_context to keep locks with different duration in different lists. Changed code handling ticket list to take this into account. * Changed methods responsible for releasing locks to take into account duration of tickets. Particularly public MDL_context::release_lock() method now only can release tickets with explicit duration (there is still internal method which allows to specify duration). To release locks with statement or transaction duration one have to use release_statement/transactional_locks() methods. * Concept of savepoint for MDL subsystem now has to take into account locks with statement duration. Consequently MDL_savepoint class was introduced and methods working with savepoints were updated accordingly. * Added methods which allow to set duration for one or all locks in the context. sql/mysqld.cc: Removed global mutex and condition variables which were used by old implementation of GRL. Also we no longer need to initialize Events::LOCK_event_metadata mutex as it was replaced with metadata locks on events. sql/mysqld.h: Removed global variable, mutex and condition variables which were used by old implementation of GRL. sql/rpl_rli.cc: When slave thread closes tables which were open for handling of RBR events ensure that it releases global IX lock which was acquired as protection against GRL. sql/sp.cc: Adjusted code to the new signature of lock_object/routine_name(), to the fact that one now needs specify duration of lock when initializing MDL_request and to the fact that savepoints for MDL subsystem are now represented by MDL_savepoint class. sql/sp_head.cc: Ensure that statements in stored procedures release statement metadata locks and thus release their protectiong against GRL in proper moment in time. Adjusted code to the fact that one now needs specify duration of lock when initializing MDL_request. sql/sql_admin.cc: Adjusted code to the fact that one now needs specify duration of lock when initializing MDL_request. sql/sql_base.cc: - Implemented support for new approach to acquiring protection against global read lock. We no longer acquire such protection explicitly on the basis of statement flags. Instead we always rely on code which is responsible for acquiring metadata locks on object to be changed acquiring this protection. This is achieved by acquiring global IX metadata lock with statement duration. Code doing this also responsible for checking that current connection has no active GRL by calling an Global_read_lock::can_acquire_protection() method. Changed code in open_table() and lock_table_names() accordingly. Note that as result of this change DDL and DML on temporary tables is always compatible with GRL (before it was incompatible in some cases and compatible in other cases). - To speed-up code acquiring protection against GRL introduced m_has_protection_against_grl member in Open_table_context class. It indicates that protection was already acquired sometime during open_tables() execution and new attempts can be skipped. - Thanks to new GRL implementation calls to broadcast_refresh() became unnecessary and were removed. - Adjusted code to the fact that one now needs specify duration of lock when initializing MDL_request and to the fact that savepoints for MDL subsystem are now represented by MDL_savepoint class. sql/sql_base.h: Adjusted code to the fact that savepoints for MDL subsystem are now represented by MDL_savepoint class. Also introduced Open_table_context::m_has_protection_against_grl member which allows to avoid acquiring protection against GRL while opening tables if such protection was already acquired. sql/sql_class.cc: Changed THD::leave_locked_tables_mode() after transactional sentinel for metadata locks was obsoleted by introduction of locks with explicit duration. sql/sql_class.h: - Adjusted code to the fact that savepoints for MDL subsystem are now represented by MDL_savepoint class. - Changed Global_read_lock class according to changes in global read lock implementation: * wait_if_global_read_lock and start_waiting_global_read_lock are now gone. Instead code needing protection against GRL has to acquire global IX metadata lock with statement duration itself. To help it new can_acquire_protection() was introduced. Also as result of the above change m_protection_count member is gone too. * Added m_mdl_blocks_commits_lock member to store metadata lock blocking commits. * Adjusted code to the fact that concept of transactional sentinel was obsoleted by concept of lock duration. - Removed CF_PROTECT_AGAINST_GRL flag as it is no longer necessary. New GRL implementation acquires protection against global read lock automagically when statement acquires metadata locks on tables or other objects it is going to change. sql/sql_db.cc: Adjusted code to the fact that one now needs specify duration of lock when initializing MDL_request. sql/sql_handler.cc: Removed call to broadcast_refresh() function. It is no longer needed with new GRL implementation. Adjusted code after introducing duration concept for metadata locks. Particularly to the fact transactional sentinel was replaced with explicit duration. sql/sql_handler.h: Renamed mysql_ha_move_tickets_after_trans_sentinel() to mysql_ha_set_explicit_lock_duration() after transactional sentinel was obsoleted by locks with explicit duration. sql/sql_insert.cc: Adjusted code handling delaying inserts after switching to new GRL implementation. Now connection thread initiating delayed insert has to acquire global IX lock in addition to metadata lock on table being inserted into. This IX lock protects against GRL and similarly to SW lock on table being inserted into has to be passed to handler thread in order to avoid deadlocks. sql/sql_lex.cc: LEX::protect_against_global_read_lock member is no longer necessary since protection against GRL is automatically taken by code acquiring metadata locks/opening tables. sql/sql_lex.h: LEX::protect_against_global_read_lock member is no longer necessary since protection against GRL is automatically taken by code acquiring metadata locks/opening tables. sql/sql_parse.cc: - Implemented support for new approach to acquiring protection against global read lock. We no longer acquire such protection explicitly on the basis of statement flags. Instead we always rely on code which is responsible for acquiring metadata locks on object to be changed acquiring this protection. This is achieved by acquiring global IX metadata lock with statement duration. This lock is automatically released at the end of statement execution. - Changed implementation of CREATE/DROP PROCEDURE/FUNCTION not to release metadata locks and thus protection against of GRL in the middle of statement execution. - Adjusted code to the fact that one now needs specify duration of lock when initializing MDL_request and to the fact that savepoints for MDL subsystem are now represented by MDL_savepoint class. sql/sql_prepare.cc: Adjusted code to the to the fact that savepoints for MDL subsystem are now represented by MDL_savepoint class. sql/sql_rename.cc: With new GRL implementation there is no need to explicitly acquire protection against GRL before renaming tables. This happens automatically in code which acquires metadata locks on tables being renamed. sql/sql_show.cc: Adjusted code to the fact that one now needs specify duration of lock when initializing MDL_request and to the fact that savepoints for MDL subsystem are now represented by MDL_savepoint class. sql/sql_table.cc: - With new GRL implementation there is no need to explicitly acquire protection against GRL before dropping tables. This happens automatically in code which acquires metadata locks on tables being dropped. - Changed mysql_alter_table() not to release lock on new table name explicitly and to rely on automatic release of locks at the end of statement instead. This was necessary since now MDL_context::release_lock() is supported only for locks for explicit duration. sql/sql_trigger.cc: With new GRL implementation there is no need to explicitly acquire protection against GRL before changing table triggers. This happens automatically in code which acquires metadata locks on tables which triggers are to be changed. sql/sql_update.cc: Fix bug exposed by GRL testing. During prepare phase acquire only S metadata locks instead of SW locks to keep prepare of multi-UPDATE compatible with concurrent LOCK TABLES WRITE and global read lock. sql/sql_view.cc: With new GRL implementation there is no need to explicitly acquire protection against GRL before creating view. This happens automatically in code which acquires metadata lock on view to be created. sql/sql_yacc.yy: LEX::protect_against_global_read_lock member is no longer necessary since protection against GRL is automatically taken by code acquiring metadata locks/opening tables. sql/table.cc: Adjusted code to the fact that one now needs specify duration of lock when initializing MDL_request. sql/table.h: Adjusted code to the fact that one now needs specify duration of lock when initializing MDL_request. sql/transaction.cc: Replaced custom implementation of global read lock with one based on metadata locks. Consequently when doing commit instead of calling method of Global_read_lock class to acquire protection against GRL we simply acquire IX in COMMIT namespace. Also adjusted code to the fact that MDL savepoint is now represented by MDL_savepoint class.	2010-11-11 20:11:05 +03:00
Davi Arnaut	a5efb91dea	Bug#49938: Failing assertion: inode or deadlock in fsp/fsp0fsp.c ... Bug#54678: InnoDB, TRUNCATE, ALTER, I_S SELECT, crash or deadlock - Incompatible change: truncate no longer resorts to a row by row delete if the storage engine does not support the truncate method. Consequently, the count of affected rows does not, in any case, reflect the actual number of rows. - Incompatible change: it is no longer possible to truncate a table that participates as a parent in a foreign key constraint, unless it is a self-referencing constraint (both parent and child are in the same table). To work around this incompatible change and still be able to truncate such tables, disable foreign checks with SET foreign_key_checks=0 before truncate. Alternatively, if foreign key checks are necessary, please use a DELETE statement without a WHERE condition. Problem description: The problem was that for storage engines that do not support truncate table via a external drop and recreate, such as InnoDB which implements truncate via a internal drop and recreate, the delete_all_rows method could be invoked with a shared metadata lock, causing problems if the engine needed exclusive access to some internal metadata. This problem originated with the fact that there is no truncate specific handler method, which ended up leading to a abuse of the delete_all_rows method that is primarily used for delete operations without a condition. Solution: The solution is to introduce a truncate handler method that is invoked when the engine does not support truncation via a table drop and recreate. This method is invoked under a exclusive metadata lock, so that there is only a single instance of the table when the method is invoked. Also, the method is not invoked and a error is thrown if the table is a parent in a non-self-referencing foreign key relationship. This was necessary to avoid inconsistency as some integrity checks are bypassed. This is inline with the fact that truncate is primarily a DDL operation that was designed to quickly remove all data from a table. mysql-test/suite/innodb/t/innodb-truncate.test: Add test cases for truncate and foreign key checks. Also test that InnoDB resets auto-increment on truncate. mysql-test/suite/innodb/t/innodb.test: FK is not necessary, test is related to auto-increment. Update error number, truncate is no longer invoked if table is parent in a FK relationship. mysql-test/suite/innodb/t/innodb_mysql.test: Update error number, truncate is no longer invoked if table is parent in a FK relationship. Use delete instead of truncate, test is used to check the interaction of FKs, triggers and delete. mysql-test/suite/parts/inc/partition_check.inc: Fix typo. mysql-test/suite/sys_vars/t/foreign_key_checks_func.test: Update error number, truncate is no longer invoked if table is parent in a FK relationship. mysql-test/t/mdl_sync.test: Modify test case to reflect and ensure that truncate takes a exclusive metadata lock. mysql-test/t/trigger-trans.test: Update error number, truncate is no longer invoked if table is parent in a FK relationship. sql/ha_partition.cc: Reorganize the various truncate methods. delete_all_rows is now passed directly to the underlying engines, so as truncate. The code responsible for truncating individual partitions is moved to ha_partition::truncate_partition, which is invoked when a ALTER TABLE t1 TRUNCATE PARTITION p statement is executed. Since the partition truncate no longer can be invoked via delete, the bitmap operations are not necessary anymore. The explicit reset of the auto-increment value is also removed as the underlying engines are now responsible for reseting the value. sql/handler.cc: Wire up the handler truncate method. sql/handler.h: Introduce and document the truncate handler method. It assumes certain use cases of delete_all_rows. Add method to retrieve the list of foreign keys referencing a table. Method is used to avoid truncating tables that are parent in a foreign key relationship. sql/share/errmsg-utf8.txt: Add error message for truncate and FK. sql/sql_lex.h: Introduce a flag so that the partition engine can detect when a partition is being truncated. Used to give a special error. sql/sql_parse.cc: Function mysql_truncate_table no longer exists. sql/sql_partition_admin.cc: Implement the TRUNCATE PARTITION statement. sql/sql_truncate.cc: Change the truncate table implementation to use the new truncate handler method and to not rely on row-by-row delete anymore. The truncate handler method is always invoked with a exclusive metadata lock. Also, it is no longer possible to truncate a table that is parent in some non-self-referencing foreign key. storage/archive/ha_archive.cc: Rename method as the description indicates that in the future this could be a truncate operation. storage/blackhole/ha_blackhole.cc: Implement truncate as no operation for the blackhole engine in order to remain compatible with older releases. storage/federated/ha_federated.cc: Introduce truncate method that invokes delete_all_rows. This is required to support partition truncate as this form of truncate does not implement the drop and recreate protocol. storage/heap/ha_heap.cc: Introduce truncate method that invokes delete_all_rows. This is required to support partition truncate as this form of truncate does not implement the drop and recreate protocol. storage/ibmdb2i/ha_ibmdb2i.cc: Introduce truncate method that invokes delete_all_rows. This is required to support partition truncate as this form of truncate does not implement the drop and recreate protocol. storage/innobase/handler/ha_innodb.cc: Rename delete_all_rows to truncate. InnoDB now does truncate under a exclusive metadata lock. Introduce and reorganize methods used to retrieve the list of foreign keys referenced by a or referencing a table. storage/myisammrg/ha_myisammrg.cc: Introduce truncate method that invokes delete_all_rows. This is required in order to remain compatible with earlier releases where truncate would resort to a row-by-row delete.	2010-10-06 11:34:28 -03:00
Jon Olav Hauglid	51a81b6faf	Bug #56292 Deadlock with ALTER TABLE and MERGE tables ... ALTER TABLE on a MERGE table could cause a deadlock with two other connections if we reached a situation where: 1) A connection doing ALTER TABLE can't upgrade to MDL_EXCLUSIVE on the parent table, but holds TL_READ_NO_INSERT on the child tables. 2) A connection doing DELETE on a child table can't get TL_WRITE on it since ALTER TABLE holds TL_READ_NO_INSERT. 3) A connection doing SELECT on the parent table can't get TL_READ on the child tables since TL_WRITE is ahead in the lock queue, but holds MDL_SHARED_READ on the parent table preventing ALTER TABLE from upgrading. For regular tables, this deadlock is avoided by having ALTER TABLE take a MDL_SHARED_NO_WRITE metadata lock on the table. This prevents DELETE from acquiring MDL_SHARED_WRITE on the table before ALTER TABLE tries to upgrade to MDL_EXCLUSIVE. In the example above, SELECT would therefore not be blocked by the pending DELETE as DELETE would not be able to enter TL_WRITE in the table lock queue. This patch fixes the problem for merge tables by using the same metadata lock type for child tables as for the parent table. The child tables will in this case therefore be locked with MDL_SHARED_NO_WRITE, preventing DELETE from acquiring a metadata lock and enter into the table lock queue. Change in behavior: By taking the same metadata lock for child tables as for the parent table, LOCK TABLE on the parent table will now also implicitly lock the child tables. Since LOCK TABLE on the parent table now takes more than one metadata lock, it is possible for LOCK TABLE ... WRITE on the parent table or child tables to give ER_LOCK_DEADLOCK error. Test case added to mdl_sync.test. Merge.test/.result has been updated to reflect the change to LOCK TABLE.	2010-09-08 10:25:37 +02:00
Konstantin Osipov	29c4873ad5	Commit on behalf of Dmitry Lenev. ... Merge his patch for Bug#52044 into 5.5, and apply review comments.	2010-08-12 17:50:23 +04:00
Dmitry Lenev	00496b7acd	Fix for bug #52044 "FLUSH TABLES WITH READ LOCK and FLUSH ... TABLES <list> WITH READ LOCK are incompatible". The problem was that FLUSH TABLES <list> WITH READ LOCK which was issued when other connection has acquired global read lock using FLUSH TABLES WITH READ LOCK was blocked and has to wait until global read lock is released. This issue stemmed from the fact that FLUSH TABLES <list> WITH READ LOCK implementation has acquired X metadata locks on tables to be flushed. Since these locks required acquiring of global IX lock this statement was incompatible with global read lock. This patch addresses problem by using SNW metadata type of lock for tables to be flushed by FLUSH TABLES <list> WITH READ LOCK. It is OK to acquire them without global IX lock as long as we won't try to upgrade those locks. Since SNW locks allow concurrent statements using same table FLUSH TABLE <list> WITH READ LOCK now has to wait until old versions of tables to be flushed go away after acquiring metadata locks. Since such waiting can lead to deadlock MDL deadlock detector was extended to take into account waits for flush and resolve such deadlocks. As a bonus code in open_tables() which was responsible for waiting old versions of tables to go away was refactored. Now when we encounter old version of table in open_table() we don't back-off and wait for all old version to go away, but instead wait for this particular table to be flushed. Such approach supported by deadlock detection should reduce number of scenarios in which FLUSH TABLES aborts concurrent multi-statement transactions. Note that active FLUSH TABLES <list> WITH READ LOCK still blocks concurrent FLUSH TABLES WITH READ LOCK statement as the former keeps tables open and thus prevents the latter statement from doing flush. mysql-test/include/handler.inc: Adjusted test case after changing status which is set when FLUSH TABLES waits for tables to be flushed from "Flushing tables" to "Waiting for table". mysql-test/r/flush.result: Added test which checks that "flush tables <list> with read lock" is compatible with active "flush tables with read lock" but not vice-versa. This test also covers bug #52044 "FLUSH TABLES WITH READ LOCK and FLUSH TABLES <list> WITH READ LOCK are incompatible". mysql-test/r/mdl_sync.result: Added scenarios in which wait for table to be flushed causes deadlocks to the coverage of MDL deadlock detector. mysql-test/suite/perfschema/r/dml_setup_instruments.result: Adjusted test results after removal of COND_refresh condition variable. mysql-test/suite/perfschema/r/server_init.result: Adjusted test and its results after removal of COND_refresh condition variable. mysql-test/suite/perfschema/t/server_init.test: Adjusted test and its results after removal of COND_refresh condition variable. mysql-test/t/flush.test: Added test which checks that "flush tables <list> with read lock" is compatible with active "flush tables with read lock" but not vice-versa. This test also covers bug #52044 "FLUSH TABLES WITH READ LOCK and FLUSH TABLES <list> WITH READ LOCK are incompatible". mysql-test/t/kill.test: Adjusted test case after changing status which is set when FLUSH TABLES waits for tables to be flushed from "Flushing tables" to "Waiting for table". mysql-test/t/lock_multi.test: Adjusted test case after changing status which is set when FLUSH TABLES waits for tables to be flushed from "Flushing tables" to "Waiting for table". mysql-test/t/mdl_sync.test: Added scenarios in which wait for table to be flushed causes deadlocks to the coverage of MDL deadlock detector. sql/ha_ndbcluster.cc: Adjusted code after adding one more parameter for close_cached_tables() call - timeout for waiting for table to be flushed. sql/ha_ndbcluster_binlog.cc: Adjusted code after adding one more parameter for close_cached_tables() call - timeout for waiting for table to be flushed. sql/lock.cc: Removed COND_refresh condition variable. See comment for sql_base.cc for details. sql/mdl.cc: Now MDL deadlock detector takes into account information about waits for table flushes when searching for deadlock. To implement this change: - Declaration of enum_deadlock_weight and Deadlock_detection_visitor were moved to mdl.h header to make them available to the code in table.cc which implements deadlock detector traversal through edges of waiters graph representing waiting for flush. - Since now MDL_context may wait not only for metadata lock but also for table to be flushed an abstract Wait_for_edge class was introduced. Its descendants MDL_ticket and Flush_ticket incapsulate specifics of inspecting waiters graph when following through edge representing wait of particular type. We no longer require global IX metadata lock when acquiring SNW or SNRW locks. Such locks are needed only when metadata locks of these types are upgraded to X locks. This allows to use SNW locks in FLUSH TABLES <list> WITH READ LOCK implementation and keep the latter compatible with global read lock. sql/mdl.h: Now MDL deadlock detector takes into account information about waits for table flushes when searching for deadlock. To implement this change: - Declaration of enum_deadlock_weight and Deadlock_detection_visitor were moved to mdl.h header to make them available to the code in table.cc which implements deadlock detector traversal through edges of waiters graph representing waiting for flush. - Since now MDL_context may wait not only for metadata lock but also for table to be flushed an abstract Wait_for_edge class was introduced. Its descendants MDL_ticket and Flush_ticket incapsulate specifics of inspecting waiters graph when following through edge representing wait of particular type. - Deadlock_detection_visitor now has m_table_shares_visited member which allows to support recursive locking for LOCK_open. This is required when deadlock detector inspects waiters graph which contains several edges representing waits for flushes or needs to come through the such edge more than once. sql/mysqld.cc: Removed COND_refresh condition variable. See comment for sql_base.cc for details. sql/mysqld.h: Removed COND_refresh condition variable. See comment for sql_base.cc for details. sql/sql_base.cc: Changed approach to how threads are waiting for table to be flushed. Now thread that wants to wait for old table to go away subscribes for notification by adding Flush_ticket to table's share and waits using MDL_context::m_wait object. Once table gets flushed (i.e. all tables are closed and table share is ready to be destroyed) all such waiters are notified individually. Thanks to this change MDL deadlock detector can take such waits into account. To implement this/as result of this change: - tdc_wait_for_old_versions() was replaced with tdc_wait_for_old_version() which waits for individual old share to go away and which is called by open_table() after finding out that share is outdated. We don't need to perform back-off before such waiting thanks to the fact that deadlock detector now sees such waits. - As result Open_table_ctx::m_mdl_requests became unnecessary and was removed. We no longer allocate copies of MDL_request objects on MEM_ROOT when MYSQL_OPEN_FORCE_SHARED/SHARED_HIGH_PRIO flags are in effect. - close_cached_tables() and tdc_wait_for_old_version() share code which implements waiting for share to be flushed - the both use TABLE_SHARE::wait_until_flush() method. Thanks to this close_cached_tables() supports timeouts and has extra parameter for this. - Open_table_context::OT_MDL_CONFLICT enum element was renamed to OT_CONFLICT as it is now also used in cases when back-off is required to resolve deadlock caused by waiting for flush and not metadata lock. - In cases when we discover that current connection tries to open tables from different generation we now simply back-off and restart process of opening tables. To support this Open_table_context::OT_REOPEN_TABLES enum element was added. - COND_refresh condition variable became unnecessary and was removed. - mysql_notify_thread_having_shared_lock() no longer wakes up connections waiting for flush as all such connections can be waken up by deadlock detector if necessary. sql/sql_base.h: - close_cached_tables() now has one more parameter - timeout for waiting for table to be flushed. - Open_table_context::OT_MDL_CONFLICT enum element was renamed to OT_CONFLICT as it is now also used in cases when back-off is required to resolve deadlock caused by waiting for flush and not metadata lock. Added new OT_REOPEN_TABLES enum element to be used in cases when we need to restart open tables process even in the middle of transaction. - Open_table_ctx::m_mdl_requests became unnecessary and was removed. sql/sql_class.h: Added assert ensuring that we won't use LOCK_open mutex with THD::enter_cond(). Otherwise deadlocks can arise in MDL deadlock detector. sql/sql_parse.cc: Changed FLUSH TABLES <list> WITH READ LOCK to take SNW metadata locks instead of X locks on tables to be flushed. Since we no longer require global IX lock to be taken when SNW locks are taken this makes this statement compatible with FLUSH TABLES WITH READ LOCK statement. Since SNW locks allow other connections to have table opened FLUSH TABLES <list> WITH READ LOCK now has to wait during open_tables() for old version to go away. Such waits can lead to deadlocks which will be detected by MDL deadlock detector which now takes waits for table to be flushed into account. Also adjusted code after adding one more parameter for close_cached_tables() call - timeout for waiting for table to be flushed. sql/sql_yacc.yy: FLUSH TABLES <list> WITH READ LOCK now needs only SNW metadata locks on tables. sql/sys_vars.cc: Adjusted code after adding one more parameter for close_cached_tables() call - timeout for waiting for table to be flushed. sql/table.cc: Implemented new approach to how threads are waiting for table to be flushed. Now thread that wants to wait for old table to go away subscribes for notification by adding Flush_ticket to table's share and waits using MDL_context::m_wait object. Once table gets flushed (i.e. all tables are closed and table share is ready to be destroyed) all such waiters are notified individually. This change allows to make such waits visible inside of MDL deadlock detector. To do it: - Added list of waiters/Flush_tickets to TABLE_SHARE class. - Changed free_table_share() to postpone freeing of share memory until last waiter goes away and to wake up subscribed waiters. - Added TABLE_SHARE::wait_until_flushed() method which implements subscription to the list of waiters for table to be flushed and waiting for this event. Implemented interface which allows to expose waits for flushes to MDL deadlock detector: - Introduced Flush_ticket class a descendant of Wait_for_edge class. - Added TABLE_SHARE::find_deadlock() method which allows deadlock detector to find out what contexts are still using old version of table in question (i.e. to find out what contexts are waited for by owner of Flush_ticket). sql/table.h: In order to support new strategy of waiting for table flush (see comment for table.cc for details) added list of waiters/Flush_tickets to TABLE_SHARE class. Implemented interface which allows to expose waits for flushes to MDL deadlock detector: - Introduced Flush_ticket class a descendant of Wait_for_edge class. - Added TABLE_SHARE::find_deadlock() method which allows deadlock detector to find out what contexts are still using old version of table in question (i.e. to find out what contexts are waited for by owner of Flush_ticket).	2010-07-27 17:34:58 +04:00
Jon Olav Hauglid	3ffa8b3b90	Followup to Bug #54360 Deadlock DROP/ALTER/CREATE DATABASE ... with open HANDLER Fixes problem which caused mdl_sync.test to fail on Solaris and Windows due to path name differences in error messages in the result file.	2010-07-02 11:26:27 +02:00
Jon Olav Hauglid	9ff272fbbd	A 5.5 version of the fix for Bug #54360 "Deadlock DROP/ALTER/CREATE ... DATABASE with open HANDLER" Remove LOCK_create_db, database name locks, and use metadata locks instead. This exposes CREATE/DROP/ALTER DATABASE statements to the graph-based deadlock detector in MDL, and paves the way for a safe, deadlock-free implementation of RENAME DATABASE. Database DDL statements will now take exclusive metadata locks on the database name, while table/view/routine DDL statements take intention exclusive locks on the database name. This prevents race conditions between database DDL and table/view/routine DDL. (e.g. DROP DATABASE with concurrent CREATE/ALTER/DROP TABLE) By adding database name locks, this patch implements WL#4450 "DDL locking: CREATE/DROP DATABASE must use database locks" and WL#4985 "DDL locking: namespace/hierarchical locks". The patch also changes code to use init_one_table() where appropriate. The new lock_table_names() function requires TABLE_LIST::db_length to be set correctly, and this is taken care of by init_one_table(). This patch also adds a simple template to help work with the mysys HASH data structure. Most of the patch was written by Konstantin Osipov.	2010-07-01 15:53:46 +02:00
Dmitry Lenev	9dbd9ce185	Patch that changes approach to how we acquire metadata ... locks for DML statements and changes the way MDL locks are acquired/granted in contended case. Instead of backing-off when a lock conflict is encountered and waiting for it to go away before restarting open_tables() process we now wait for lock to be released without releasing any previously acquired locks. If conflicting lock goes away we resume opening tables. If waiting leads to a deadlock we try to resolve it by backing-off and restarting open_tables() immediately. As result both waiting for possibility to acquire and acquiring of a metadata lock now always happen within the same MDL API call. This has allowed to make release of a lock and granting it to the most appropriate pending request an atomic operation. Thanks to this it became possible to wake up during release of lock only those waiters which requests can be satisfied at the moment as well as wake up only one waiter in case when granting its request would prevent all other requests from being satisfied. This solves thundering herd problem which occured in cases when we were releasing some lock and woke up many waiters for SNRW or X locks (this was the issue in bug#52289 "performance regression for MyISAM in sysbench OLTP_RW test". This also allowed to implement more fair (FIFO) scheduling among waiters with the same priority. It also opens the door for introducing new types of requests for metadata locks such as low-prio SNRW lock which is necessary in order to support LOCK TABLES LOW_PRIORITY WRITE. Notice that after this sometimes can report ER_LOCK_DEADLOCK error in cases in which it has not happened before. Particularly we will always report this error if waiting for conflicting lock has happened in the middle of transaction and resulted in a deadlock. Before this patch the error was not reported if deadlock could have been resolved by backing off all metadata locks acquired by the current statement. mysql-test/r/mdl_sync.result: Added test coverage for some aspects of deadlock handling in metadata locking subsystem. Adjusted test case after removing back-off in general case when conflicting metadata lock is encountered during open_tables() (now this happens only if waiting for conflicting lock to go away leads to a deadlock). mysql-test/r/sp_sync.result: Adjusted test case after removing back-off in general case when conflicting metadata lock is encountered during open_tables() (now this happens only if waiting for conflicting lock to go away leads to a deadlock). mysql-test/suite/perfschema/r/dml_setup_instruments.result: Adjusted test results after renaming MDL_context:: m_waiting_for_lock rwlock to m_LOCK_waiting_for. mysql-test/suite/rpl/r/rpl_sp.result: Adjusted test case after implementing new approach to acquiring metadata locks in open_tables(). We no longer release all MDL locks acquired by statement before waiting for conflicting lock to go away. As result DROP FUNCTION statement has to wait for DML statement which managed to acquire metadata lock on function being dropped and now waits for other conflicting metadata lock to go away. mysql-test/suite/rpl/t/rpl_sp.test: Adjusted test case after implementing new approach to acquiring metadata locks in open_tables(). We no longer release all MDL locks acquired by statement before waiting for conflicting lock to go away. As result DROP FUNCTION statement has to wait for DML statement which managed to acquire metadata lock on function being dropped and now waits for other conflicting metadata lock to go away. mysql-test/t/mdl_sync.test: Added test coverage for some aspects of deadlock handling in metadata locking subsystem. Adjusted test case after removing back-off in general case when conflicting metadata lock is encountered during open_tables() (now this happens only if waiting for conflicting lock to go away leads to a deadlock). mysql-test/t/sp_sync.test: Adjusted test case after removing back-off in general case when conflicting metadata lock is encountered during open_tables() (now this happens only if waiting for conflicting lock to go away leads to a deadlock). sql/mdl.cc: Changed MDL subsystem to support new approach to acquring metadata locks in open tables and more fair and efficient scheduling of metadata locks. To implement this: - Made releasing of the lock and granting it to the most appropriate pending request atomic operation. As result it became possible to wake up only those waiters requests from which can be satisfied at the moment as well as wake-up only one waiter in case when granting its request would prevent all other requests from being satisfied. This solved thundering herd problem which occured in cases when we were releasing some lock and woke up many waiters for SNRW or X locks (this was the issue in Bug #52289 "performance regression for MyISAM in sysbench OLTP_RW test". To emphasize above changes wake_up_waiters() was renamed to MDL_context::reschedule_waiters(). - Changed code to add tickets for new requests to the back of waiters queue and to select tickets to be satisfied from the head of the queue if possible (this makes scheduling of requests with the same priority fair). To be able to do this efficiently we now use for waiting and granted queues version of I_P_List class which provides fast push_back() method. - Members and methods of MDL_context related to sending and waiting for signal were moved to separate MDL_wait class. - Since in order to avoid race conditions we must grant the lock only to the context which was not chosen as a victim of deadlock, killed or aborted due to timeout MDL_wait::set_status() (former awake()) was changed not to send signal if signal slot is already occupied and to indicate this fact through its return value. As another consequence MDL_wait::timed_wait() method was changed to handle timeout (optionally) and abort due to kill as signals which make signal slot occupied. - Renamed MDL_context::acquire_lock_impl() to acquire_lock(). Changed it to be able correctly process requests for shared locks when there are open HANDLERs, made this method more optimized for acquisition of shared locks. As part of this change moved code common between try_acquire_lock() and acquire_lock() to new try_acquire_lock_impl() method. Also adjusted acquire_lock()'s code to take into account the fact that in cases when lock is granted as result of MDL_context::reschedule_waiters() call (i.e. when it is granted after waiting for lock conflict to go away) updating MDL_lock state is responsibility of the thread calling reschedule_waiters(). - Changed MDL_context::find_deadlock() to send VICTIM signal even if victim is the context which has initiated deadlock detection. This is required in order to avoid races in cases when the same context simultaneously is chosen as a victim and its request for lock is satisfied. As result return value of this method became unnecessary and it was changed to return void. Adjusted MDL_lock::find_deadlock() method to take into account that now there can be a discrepancy between MDL_context::m_waiting_for value being set and real state of the ticket this member points to. - Renamed MDL_context::m_waiting_for_lock to m_LOCK_waiting_for and MDL_context::stop_waiting() to done_waiting_for(). - Finally, removed MDL_context::wait_for_lock() method. sql/mdl.h: Changed MDL subsystem to support new approach to acquring metadata locks in open tables and more fair and efficient scheduling of metadata locks. To implement this: - Members and methods of MDL_context related to sending and waiting for signal were moved to separate MDL_wait class. - Since now in order to avoid race conditions we must grant the lock only to the context which was not chosen as a victim of deadlock, killed or aborted due to timeout MDL_wait::set_status (former awake()) was changed not to send signal if signal slot is already occupied and to indicate this fact through its return value. Also NORMAL_WAKE_UP signal became GRANTED, and timeouts and aborts due to kill became full blown signals rather than simple return values. - MDL_wait::timed_wait() now takes extra parameter that indicates whether signal should be set if timeout is reached. - Enabled fast push_back() operation in MDL_context::m_tickets list to make move_ticket_after_trans_sentinel() method more efficient. - Removed MDL_context::wait_for_lock() method. - Renamed MDL_context::m_waiting_for_lock to m_LOCK_waiting_for and MDL_context::stop_waiting() to done_waiting_for(). - MDL_context::acquire_lock_impl() became acquire_lock(). - Introduced MDL_context::try_acquire_lock_impl() as a place for code shared by try_acquire_lock and acquire_lock(). - Due to fact that now VICTIM signal is sent even if victim is the context which has initiated deadlock detection find_deadlock() no longer needs a return value. sql/sql_base.cc: Implemented new approach to acquiring metadata locks in open_tables(). We no longer perform back-off when conflicting metadata lock is encountered. Instead we wait for this lock to go away while holding all locks which were acquired so far. Back-off is only used in situation when further waiting will cause a deadlock which could be avoided by performing back-off and restarting open_tables() process. Absence of waiting between back-off and restart of acquiring metadata locks can't lead to livelocks as MDL subsystem was changed to make release of lock and granting it to waiting lock an atomic action, so back-off will automatically give way to other participants of deadlock loop. Accordingly: - open_table_get_mdl_lock() and open_and_process_routine() were changed to wait for conflicting metadata lock to go away without back-off. Only if such wait leads to a deadlock back-off is requested. As part of this change new error handler class was introduced which converts, if possible, ER_LOCK_DEADLOCK error to a request for back-off and re-start of open_tables() process. - Open_table_context::recover_from_failed_open() was changed not to wait in case of metadata lock conflict. Instead we immediately proceed to re-acquiring locks. - Open_table_context::request_backoff_action() now always emits error if back-off is requested in the middle of transaction as we can't be sure that releasing lock which were acquired only by current statement will resolve a deadlock. Before this patch such situations were successfully detected thanks to the fact that we called MDL_context::wait_for_lock() method in recover_from_failed_open(). - In order to avoid deadlocks open_tables() code was adjusted to flush open HANDLERs for which there are pending requests for X locks before restarting the process of acquiring metadata locks. - Changed close_tables_for_reopen() not to reset MDL_request for tables belonging to the tail of prelocking list. It is no longer necessary as these MDL_request objects won't be used for any waiting. - Adjusted comment in tdc_wait_for_old_version() to avoid mentioning removed MDL_context::wait_for_lock() method. sql/sql_base.h: As we no longer wait for conflicting metadata lock away in Open_table_context::recover_from_failed_open() method, Open_table_context::OT_WAIT_MDL_LOCK action was renamed to OT_MDL_CONFLICT. Also Open_table_context::m_failed_mdl_request became unnecessary and was removed. sql/sql_plist.h: Extended I_P_List template to support efficient push_back() operation if it is parameterized with an appropriate policy class. sql/sql_show.cc: Adjusted code after removal of MDL_context::wait_for_lock() method. Now if one needs to acquire metadata lock with waiting one has to use a variant of MDL_context::acquire_lock() method.	2010-06-07 11:06:55 +04:00
Jon Olav Hauglid	142a162c66	manual merge from mysql-trunk-bugfixing ... Conflicts: Text conflict in mysql-test/r/archive.result Contents conflict in mysql-test/r/innodb_bug38231.result Text conflict in mysql-test/r/mdl_sync.result Text conflict in mysql-test/suite/binlog/t/disabled.def Text conflict in mysql-test/suite/rpl_ndb/r/rpl_ndb_binlog_format_errors.result Text conflict in mysql-test/t/archive.test Contents conflict in mysql-test/t/innodb_bug38231.test Text conflict in mysql-test/t/mdl_sync.test Text conflict in sql/sp_head.cc Text conflict in sql/sql_show.cc Text conflict in sql/table.cc Text conflict in sql/table.h	2010-06-06 13:19:29 +02:00
Sergey Glukhov	07f07ffed1	test case fix	2010-05-31 12:38:45 +04:00
Sergey Glukhov	8fa381fda3	Bug#52856 concurrent show columns or show full columns causes a crash!!!1 ... We should avoid any SHARE fields assignments as this is shared structure and assignments may affect other therads. To avoid this copy of SHARE struct is created and stored into TABLE struct which is used in get_schema_coulumns_record later. mysql-test/r/mdl_sync.result: test case mysql-test/t/mdl_sync.test: test case sql/sql_show.cc: We should avoid any SHARE fields assignments as this is shared structure and assignments may affect other therads. To avoid this copy of SHARE struct is created and stored into TABLE struct which is used in get_schema_coulumns_record later.	2010-05-27 19:54:43 +04:00
Dmitry Lenev	2397d7fe19	Fix for bug #53238 "mdl_sync fails sporadically". ... The problem was that mdl_sync.test was failing sporadically, due to fact that part of the test didn't take into account effects of MyISAM's concurrent insert. This patch solves the problem by making test case robust against concurrent insert.	2010-05-26 23:58:16 +04:00
Davi Arnaut	4f18083b08	Bug#42643: InnoDB does not support replication of TRUNCATE TABLE ... The problem was that TRUNCATE TABLE didn't take a exclusive lock on a table if it resorted to truncating via delete of all rows in the table. Specifically for InnoDB tables, this could break proper isolation as InnoDB ends up aborting some granted locks when truncating a table. The solution is to take a exclusive metadata lock before TRUNCATE TABLE can proceed. This guarantees that no other transaction is using the table. Incompatible change: Truncate via delete no longer fails if sql_safe_updates is activated (this was a undocumented side effect). libmysqld/CMakeLists.txt: Add new files to the build list. libmysqld/Makefile.am: Add new files to the build list. mysql-test/extra/binlog_tests/binlog_truncate.test: Add test case for Bug#42643 mysql-test/include/mix1.inc: Update test case as TRUNCATE TABLE now grabs a exclusive lock. Ensure that TRUNCATE waits for granted locks on the table. mysql-test/suite/binlog/t/binlog_truncate_innodb.test: As with other data modifying statements, TRUNCATE is still not possible in a transaction with isolation level READ COMMITTED or READ UNCOMMITED. It would be possible to implement so, but it is not worth the effort. mysql-test/suite/binlog/t/binlog_truncate_myisam.test: Test under different binlog formats. mysql-test/suite/binlog/t/disabled.def: Re-enable test case. mysql-test/t/innodb_bug38231.test: Truncate no longer works with row-level locks. mysql-test/t/mdl_sync.test: Ensure that a acquired lock is not given up due to a conflict. mysql-test/t/partition_innodb_semi_consistent.test: End transaction as to release metadata locks. mysql-test/t/truncate.test: A metadata lock is now taken before the object is verified. sql/CMakeLists.txt: Add new files to the build list. sql/Makefile.am: Add new files to the build list. sql/datadict.cc: Introduce a new file specific for data dictionary operations. sql/datadict.h: Add header file. sql/sql_base.cc: Rename data dictionary function. sql/sql_bitmap.h: Include dependency. sql/sql_delete.cc: Move away from relying on mysql_delete() to delete all rows of a table. Thus, move any bits related to truncate to sql_truncate.cc sql/sql_delete.h: Remove parameter. sql/sql_parse.cc: Add protection against the global read lock -- a intention exclusive lock can be acquired in the truncate path. sql/sql_show.cc: Add sync point for testing scenarios where a pending flush is ignored. sql/sql_truncate.cc: Acquire a shared metadata lock before accessing table metadata. Upgrade the lock to a exclusive one if the table can be re-created. Rework binlog rules to better reflect the requirements. sql/sql_yacc.yy: Set appropriate lock types for table to be truncated. sql/table.h: Move to data dictionary header.	2010-05-25 17:01:38 -03:00
Konstantin Osipov	7116431a8a	A review comment for the fix for Bug#46672. ... Remove unnecessary need_reopen loops.	2010-03-13 13:58:27 +03:00
Alexander Nozdrin	d1ad316a59	Patch for WL#3736: Extended Table, Column and Index Comments. ... The task is to (a) add a comment on indexes and (b) increase the maximum length of column, table and the new index comments. The patch committed on behalf of Yoshinori Matsunobu (Yoshinori.Matsunobu@Sun.COM).	2010-02-20 13:07:32 +03:00
Dmitry Lenev	96344befd3	Fix for bug #50998 "Deadlock in MDL code during test ... rqg_mdl_stability". When start of statement's waiting on a metadata lock created more than one loop in waiters graph server might have entered deadlock condition. The problem was that in the case described above MDL deadlock detector had to perform several searches for deadlock but forgot to reset Deadlock_detection_context before performing new search. Failure to do so has broken assumption in code resposible for choosing victim that if Deadlock_detection_context::victim is set we also have read lock on m_waiting_for_lock for this context. As result this lock could have been unlocked more times than it was acquired which corrupted rwlock's state which led to server deadlock. This fix ensures that such reset is done before each attempt to find a deadlock. mysql-test/r/mdl_sync.result: Added test for bug #50998 "Deadlock in MDL code during test rqg_mdl_stability" as well as coverage for the case when addition of statement waiting for metadata lock adds several loops in the waiters graph and therefore several searches for deadlock should be performed by MDL deadlock detector. mysql-test/t/mdl_sync.test: Added test for bug #50998 "Deadlock in MDL code during test rqg_mdl_stability" as well as coverage for the case when addition of statement waiting for metadata lock adds several loops in the waiters graph and therefore several searches for deadlock should be performed by MDL deadlock detector. sql/mdl.cc: Ensure that in cases when MDL deadlock detector had to perform several searches for deadlock because several loops in waiters graph are possible we reset Deadlock_detection_context before performing each search. Failure to do so has broken assumption in code resposible for choosing victim that if Deadlock_detection_context::victim is set we also have read lock on m_waiting_for_lock for this context. As result this lock could have been unlocked more times than it was acquired which corrupted rwlock's state (no one was able to acquire write lock on it anymore).	2010-02-10 18:46:03 +03:00
Dmitry Lenev	8018ec5adb	Fix for bug #50913 "Deadlock between open_and_lock_tables_derived ... and MDL". Concurrent execution of a multi-DELETE statement and ALTER TABLE statement which affected one of the tables used in the multi-DELETE sometimes led to deadlock. Similar deadlocks might have occured when one performed INSERT/UPDATE/DELETE on a view and concurrently executed ALTER TABLE for the view's underlying table, or when one concurrently executed TRUNCATE TABLE for InnoDB table and ALTER TABLE for the same table. These deadlocks were caused by a discrepancy between types of metadata and thr_lock.cc locks acquired by those statements. What happened was that multi-DELETE/TRUNCATE/DML-through-the- view statement in the first connection acquired SR lock on a table, then ALTER TABLE would come in in the second connection and acquire SNW metadata lock and TL_WRITE_ALLOW_READ thr_lock.c lock and then would start waiting for the first connection during lock upgrade. After that the statement in the first connection would try to acquire TL_WRITE lock on table and would start waiting for the second connection, creating a deadlock. This patch solves this problem by ensuring that we acquire SW metadata lock in all cases in which we acquiring write thr_lock.c lock. This guarantees that deadlocks like the one described above won't occur since all lock conflicts in such situation are resolved within MDL subsystem. This patch also adds assert which should guarantee that such situations won't arise in future. mysql-test/r/lock_multi.result: Added main test for bug #50913 "Deadlock between open_and_lock_tables_derived and MDL". mysql-test/r/mdl_sync.result: Added additional coverage for bug #50913 "Deadlock between open_and_lock_tables_derived and MDL". mysql-test/t/lock_multi.test: Added main test for bug #50913 "Deadlock between open_and_lock_tables_derived and MDL". mysql-test/t/mdl_sync.test: Added additional coverage for bug #50913 "Deadlock between open_and_lock_tables_derived and MDL". sql/lock.cc: Added assert that enforces that when we are locking a non-temporary table we have an appropriate type of metadata lock on this table. sql/mysql_priv.h: Added separate flag for open_tables() to be able specify that SH metadata locks on table to be open should be acquired. We can no longer use MYSQL_LOCK_IGNORE_FLUSH flag for this as in addition to use in I_S implementation it is also used for opening system tables. Since in the latter case we also acquire thr_lock.c locks using SH metadata lock in it instead of SR or SW locks may lead to deadlock. sql/sql_base.cc: When opening tables don't interpret MYSQL_LOCK_IGNORE_FLUSH flag as request to acquire SH metadata locks. This flag is also used for opening system tables for which we also take thr_lock.c locks and thus proper metadata lock to take in this case is SR or SW lock (otherwise deadlocks can occur). In cases when SH lock is really required (e.g. when tables are open by I_S implementation) we rely on that newly introduced MYSQL_OPEN_FORCE_SHARED_HIGH_PRIO_MDL flag is used. sql/sql_delete.cc: mysql_truncate_by_delete(): Adjust type of metadata lock to be requested after changing type of thr_lock.c lock for table list element from one which was set in parser to TL_WRITE. This removes discrepancy between types of these locks which allowed deadlocks to creep in. sql/sql_handler.cc: When closing table which was open by HANDLER statement clear TABLE::open_by_handler flag. This allows to use this flag as a reliable indication that TABLE instance was open by HANDLER statement in assert which was added to mysql_lock_tables(). sql/sql_parse.cc: multi_delete_set_locks_and_link_aux_tables(): Adjust type of metadata lock to be requested after changing type of thr_lock.c lock for table list element from one which was set in parser to TL_WRITE. This removes discrepancy between types of these locks which allowed deadlocks to creep in. sql/sql_show.cc: Use newly introduced MYSQL_OPEN_FORCE_SHARED_HIGH_PRIO_MDL flag in order to acquire SH metadata locks when opening tables in I_S implementation. sql/sql_update.cc: Added comment explaining why in multi-update after deciding that we need weaker thr_lock.c lock on a table we don't downgrade metadata lock on it. sql/sql_view.cc: When merging view into main statement adjust type of metadata lock to be requested after changing type of thr_lock.c lock for table. This removes discrepancy between types of these locks which allowed deadlocks to creep in.	2010-02-08 23:19:55 +03:00
Konstantin Osipov	a009a4e518	next-mr -> next-4284 merge: ... Change the error code for ER_WARN_I_S_SKIPPED_TABLE, to not upset the tests that rely on ER_SLAVE_CONVERSION_ERROR error code = 1667. Fix a merge bug with binlogging of CREATE TABLE (temporary tables).	2010-02-05 17:58:43 +03:00
Jon Olav Hauglid	b417300c9a	Bug #50786 Assertion `thd->mdl_context.trans_sentinel() == __null' ... failed in open_ltable() The problem was too restrictive asserts that enforced that open_ltable() was called without any active HANDLERs, LOCK TABLES or global read locks. However, this can happen in several cases when opening system tables. The assert would, for example, be triggered when drop function was called from a connection with active HANDLERs as this would cause open_ltable() to be called for mysql.proc. The assert could also be triggered when using table-based general log (mysql.general_log). This patch removes the asserts since they will be triggered in several legitimate cases and because the asserts are no longer relevant due to changes in how locks are released. The patch also fixes set_needs_thr_lock_abort() that before ignored its parameter and always set the member variable to TRUE. Test case added to mdl_sync.test. Thanks to Dmitry Lenev for help with this bug!	2010-02-03 15:09:27 +01:00
Dmitry Lenev	eba5d30e67	Implement new type-of-operation-aware metadata locks. ... Add a wait-for graph based deadlock detector to the MDL subsystem. Fixes bug #46272 "MySQL 5.4.4, new MDL: unnecessary deadlock" and bug #37346 "innodb does not detect deadlock between update and alter table". The first bug manifested itself as an unwarranted abort of a transaction with ER_LOCK_DEADLOCK error by a concurrent ALTER statement, when this transaction tried to repeat use of a table, which it has already used in a similar fashion before ALTER started. The second bug showed up as a deadlock between table-level locks and InnoDB row locks, which was "detected" only after innodb_lock_wait_timeout timeout. A transaction would start using the table and modify a few rows. Then ALTER TABLE would come in, and start copying rows into a temporary table. Eventually it would stumble on the modified records and get blocked on a row lock. The first transaction would try to do more updates, and get blocked on thr_lock.c lock. This situation of circular wait would only get resolved by a timeout. Both these bugs stemmed from inadequate solutions to the problem of deadlocks occurring between different locking subsystems. In the first case we tried to avoid deadlocks between metadata locking and table-level locking subsystems, when upgrading shared metadata lock to exclusive one. Transactions holding the shared lock on the table and waiting for some table-level lock used to be aborted too aggressively. We also allowed ALTER TABLE to start in presence of transactions that modify the subject table. ALTER TABLE acquires TL_WRITE_ALLOW_READ lock at start, and that block all writes against the table (naturally, we don't want any writes to be lost when switching the old and the new table). TL_WRITE_ALLOW_READ lock, in turn, would block the started transaction on thr_lock.c lock, should they do more updates. This, again, lead to the need to abort such transactions. The second bug occurred simply because we didn't have any mechanism to detect deadlocks between the table-level locks in thr_lock.c and row-level locks in InnoDB, other than innodb_lock_wait_timeout. This patch solves both these problems by moving lock conflicts which are causing these deadlocks into the metadata locking subsystem, thus making it possible to avoid or detect such deadlocks inside MDL. To do this we introduce new type-of-operation-aware metadata locks, which allow MDL subsystem to know not only the fact that transaction has used or is going to use some object but also what kind of operation it has carried out or going to carry out on the object. This, along with the addition of a special kind of upgradable metadata lock, allows ALTER TABLE to wait until all transactions which has updated the table to go away. This solves the second issue. Another special type of upgradable metadata lock is acquired by LOCK TABLE WRITE. This second lock type allows to solve the first issue, since abortion of table-level locks in event of DDL under LOCK TABLES becomes also unnecessary. Below follows the list of incompatible changes introduced by this patch: - From now on, ALTER TABLE and CREATE/DROP TRIGGER SQL (i.e. those statements that acquire TL_WRITE_ALLOW_READ lock) wait for all transactions which has *updated* the table to complete. - From now on, LOCK TABLES ... WRITE, REPAIR/OPTIMIZE TABLE (i.e. all statements which acquire TL_WRITE table-level lock) wait for all transaction which *updated or read* from the table to complete. As a consequence, innodb_table_locks=0 option no longer applies to LOCK TABLES ... WRITE. - DROP DATABASE, DROP TABLE, RENAME TABLE no longer abort statements or transactions which use tables being dropped or renamed, and instead wait for these transactions to complete. - Since LOCK TABLES WRITE now takes a special metadata lock, not compatible with with reads or writes against the subject table and transaction-wide, thr_lock.c deadlock avoidance algorithm that used to ensure absence of deadlocks between LOCK TABLES WRITE and other statements is no longer sufficient, even for MyISAM. The wait-for graph based deadlock detector of MDL subsystem may sometimes be necessary and is involved. This may lead to ER_LOCK_DEADLOCK error produced for multi-statement transactions even if these only use MyISAM: session 1: session 2: begin; update t1 ... lock table t2 write, t1 write; -- gets a lock on t2, blocks on t1 update t2 ... (ER_LOCK_DEADLOCK) - Finally, support of LOW_PRIORITY option for LOCK TABLES ... WRITE was abandoned. LOCK TABLE ... LOW_PRIORITY WRITE from now on has the same priority as the usual LOCK TABLE ... WRITE. SELECT HIGH PRIORITY no longer trumps LOCK TABLE ... WRITE in the wait queue. - We do not take upgradable metadata locks on implicitly locked tables. So if one has, say, a view v1 that uses table t1, and issues: LOCK TABLE v1 WRITE; FLUSH TABLE t1; -- (or just 'FLUSH TABLES'), an error is produced. In order to be able to perform DDL on a table under LOCK TABLES, the table must be locked explicitly in the LOCK TABLES list. mysql-test/include/handler.inc: Adjusted test case to trigger an execution path on which bug 41110 "crash with handler command when used concurrently with alter table" and bug 41112 "crash in mysql_ha_close_table/get_lock_data with alter table" were originally discovered. Left old test case which no longer triggers this execution path for the sake of coverage. Added test coverage for HANDLER SQL statements and type-aware metadata locks. Added a test for the global shared lock and HANDLER SQL. Updated tests to take into account that the old simple deadlock detection heuristics was replaced with a graph-based deadlock detector. mysql-test/r/debug_sync.result: Updated results (see debug_sync.test). mysql-test/r/handler_innodb.result: Updated results (see handler.inc test). mysql-test/r/handler_myisam.result: Updated results (see handler.inc test). mysql-test/r/innodb-lock.result: Updated results (see innodb-lock.test). mysql-test/r/innodb_mysql_lock.result: Updated results (see innodb_mysql_lock.test). mysql-test/r/lock.result: Updated results (see lock.test). mysql-test/r/lock_multi.result: Updated results (see lock_multi.test). mysql-test/r/lock_sync.result: Updated results (see lock_sync.test). mysql-test/r/mdl_sync.result: Updated results (see mdl_sync.test). mysql-test/r/sp-threads.result: SHOW PROCESSLIST output has changed due to the fact that waiting for LOCK TABLES WRITE now happens within metadata locking subsystem. mysql-test/r/truncate_coverage.result: Updated results (see truncate_coverage.test). mysql-test/suite/funcs_1/datadict/processlist_val.inc: SELECT FROM I_S.PROCESSLIST output has changed due to fact that waiting for LOCK TABLES WRITE now happens within metadata locking subsystem. mysql-test/suite/funcs_1/r/processlist_val_no_prot.result: SELECT FROM I_S.PROCESSLIST output has changed due to fact that waiting for LOCK TABLES WRITE now happens within metadata locking subsystem. mysql-test/suite/rpl/t/rpl_sp.test: Updated to a new SHOW PROCESSLIST state name. mysql-test/t/debug_sync.test: Use LOCK TABLES READ instead of LOCK TABLES WRITE as the latter no longer allows to trigger execution path involving waiting on thr_lock.c lock and therefore reaching debug sync-point covered by this test. mysql-test/t/innodb-lock.test: Adjusted test case to the fact that innodb_table_locks=0 option is no longer supported, since LOCK TABLES WRITE handles all its conflicts within MDL subsystem. mysql-test/t/innodb_mysql_lock.test: Added test for bug #37346 "innodb does not detect deadlock between update and alter table". mysql-test/t/lock.test: Added test coverage which checks the fact that we no longer support DDL under LOCK TABLES on tables which were locked implicitly. Adjusted existing test cases accordingly. mysql-test/t/lock_multi.test: Added test for bug #46272 "MySQL 5.4.4, new MDL: unnecessary deadlock". Adjusted other test cases to take into account the fact that waiting for LOCK TABLES ... WRITE now happens within MDL subsystem. mysql-test/t/lock_sync.test: Since LOCK TABLES ... WRITE now takes SNRW metadata lock for tables locked explicitly we have to implicitly lock InnoDB tables (through view) to trigger the table-level lock conflict between TL_WRITE and TL_WRITE_ALLOW_WRITE. mysql-test/t/mdl_sync.test: Added basic test coverage for type-of-operation-aware metadata locks. Also covered with tests some use cases involving HANDLER statements in which a deadlock could arise. Adjusted existing tests to take type-of-operation-aware MDL into account. mysql-test/t/multi_update.test: Update to a new SHOW PROCESSLIST state name. mysql-test/t/truncate_coverage.test: Adjusted test case after making LOCK TABLES WRITE to wait until transactions that use the table to be locked are completed. Updated to the changed name of DEBUG_SYNC point. sql/handler.cc: Global read lock functionality has been moved into a class. sql/lock.cc: Global read lock functionality has been moved into a class. Updated code to use the new MDL API. sql/mdl.cc: Introduced new type-of-operation aware metadata locks. To do this: - Changed MDL_lock to use one list for waiting requests and one list for granted requests. For each list, added a bitmap that holds information what lock types a list contains. Added a helper class MDL_lock::List to manipulate with granted and waited lists while keeping the bitmaps in sync with list contents. - Changed lock-compatibility functions to use bitmaps that define compatibility. - Introduced a graph based deadlock detector inspired by waiting_threads.c from Maria implementation. - Now that we have a deadlock detector, and no longer have a global lock to protect individual lock objects, but rather use an rw lock per object, removed redundant code for upgrade, and the global read lock. Changed the MDL API to no longer require the caller to acquire the global intention exclusive lock by means of a separate method. Removed a few more methods that became redundant. - Removed deadlock detection heuristic, it has been made obsolete by the deadlock detector. - With operation-type-aware metadata locks, MDL subsystem has become aware of potential conflicts between DDL and open transactions. This made it possible to remove calls to mysql_abort_transactions_with_shared_lock() from acquisition paths for exclusive lock and lock upgrade. Now we can simply wait for these transactions to complete without fear of deadlock. Function mysql_lock_abort() has also become unnecessary for all conflicting cases except when a DDL conflicts with a connection that has an open HANDLER. sql/mdl.h: Introduced new type-of-operation aware metadata locks. Introduced a graph based deadlock detector and supporting methods. Added comments. God rid of redundant API calls. Renamed m_lt_or_ha_sentinel to m_trans_sentinel, since now it guards the global read lock as well as LOCK TABLES and HANDLER locks. sql/mysql_priv.h: Moved the global read lock functionality into a class. Added MYSQL_OPEN_FORCE_SHARED_MDL flag which forces open_tables() to take MDL_SHARED on tables instead of metadata locks specified in the parser. We use this to allow PREPARE run concurrently in presence of LOCK TABLES ... WRITE. Added signature for find_table_for_mdl_ugprade(). sql/set_var.cc: Global read lock functionality has been moved into a class. sql/sp_head.cc: When creating TABLE_LIST elements for prelocking or system tables set the type of request for metadata lock according to the operation that will be performed on the table. sql/sql_base.cc: - Updated code to use the new MDL API. - In order to avoid locks starvation we take upgradable locks all at once. As result implicitly locked tables no longer get an upgradable lock. Consequently DDL and FLUSH TABLES for such tables is prohibited. find_write_locked_table() was replaced by find_table_for_mdl_upgrade() function. open_table() was adjusted to return TABLE instance with upgradable ticket when necessary. - We no longer wait for all locks on OT_WAIT back off action -- only on the lock that caused the wait conflict. Moreover, now we distinguish cases when we have to wait due to conflict in MDL and old version of table in TDC. - Upate mysql_notify_threads_having_share_locks() to only abort thr_lock.c waits of threads that have open HANDLERs, since lock conflicts with only these threads now can lead to deadlocks not detectable by the MDL deadlock detector. - Remove mysql_abort_transactions_with_shared_locks() which is no longer needed. sql/sql_class.cc: Global read lock functionality has been moved into a class. Re-arranged code in THD::cleanup() to simplify assert. sql/sql_class.h: Introduced class to incapsulate global read lock functionality. Now sentinel in MDL subsystem guards the global read lock as well as LOCK TABLES and HANDLER locks. Adjusted code accordingly. sql/sql_db.cc: Global read lock functionality has been moved into a class. sql/sql_delete.cc: We no longer acquire upgradable metadata locks on tables which are locked by LOCK TABLES implicitly. As result TRUNCATE TABLE is no longer allowed for such tables. Updated code to use the new MDL API. sql/sql_handler.cc: Inform MDL_context about presence of open HANDLERs. Since HANLDERs break MDL protocol by acquiring table-level lock while holding only S metadata lock on a table MDL subsystem should take special care about such contexts (Now this is the only case when mysql_lock_abort() is used). sql/sql_parse.cc: Global read lock functionality has been moved into a class. Do not take upgradable metadata locks when opening tables for CREATE TABLE SELECT as it is not necessary and limits concurrency. When initializing TABLE_LIST objects before adding them to the table list set the type of request for metadata lock according to the operation that will be performed on the table. We no longer acquire upgradable metadata locks on tables which are locked by LOCK TABLES implicitly. As result FLUSH TABLES is no longer allowed for such tables. sql/sql_prepare.cc: Use MYSQL_OPEN_FORCE_SHARED_MDL flag when opening tables during PREPARE. This allows PREPARE to run concurrently in presence of LOCK TABLES ... WRITE. sql/sql_rename.cc: Global read lock functionality has been moved into a class. sql/sql_show.cc: Updated code to use the new MDL API. sql/sql_table.cc: Global read lock functionality has been moved into a class. We no longer acquire upgradable metadata locks on tables which are locked by LOCK TABLES implicitly. As result DROP TABLE is no longer allowed for such tables. Updated code to use the new MDL API. sql/sql_trigger.cc: Global read lock functionality has been moved into a class. We no longer acquire upgradable metadata locks on tables which are locked by LOCK TABLES implicitly. As result CREATE/DROP TRIGGER is no longer allowed for such tables. Updated code to use the new MDL API. sql/sql_view.cc: Global read lock functionality has been moved into a class. Fixed results of wrong merge that led to misuse of GLR API. CREATE VIEW statement is not a commit statement. sql/table.cc: When resetting TABLE_LIST objects for PS or SP re-execution set the type of request for metadata lock according to the operation that will be performed on the table. Do the same in auxiliary function initializing metadata lock requests in a table list. sql/table.h: When initializing TABLE_LIST objects set the type of request for metadata lock according to the operation that will be performed on the table. sql/transaction.cc: Global read lock functionality has been moved into a class.	2010-02-01 14:43:06 +03:00
Dmitry Lenev	6ddd01c27a	Patch that changes metadata locking subsystem to use mutex per lock and ... condition variable per context instead of one mutex and one conditional variable for the whole subsystem. This should increase concurrency in this subsystem. It also opens the way for further changes which are necessary to solve such bugs as bug #46272 "MySQL 5.4.4, new MDL: unnecessary deadlock" and bug #37346 "innodb does not detect deadlock between update and alter table". Two other notable changes done by this patch: - MDL subsystem no longer implicitly acquires global intention exclusive metadata lock when per-object metadata lock is acquired. Now this has to be done by explicit calls outside of MDL subsystem. - Instead of using separate MDL_context for opening system tables/tables for purposes of I_S we now create MDL savepoint in the main context before opening tables and rollback to this savepoint after closing them. This means that it is now possible to get ER_LOCK_DEADLOCK error even not inside a transaction. This might happen in unlikely case when one runs DDL on one of system tables while also running DDL on some other tables. Cases when this ER_LOCK_DEADLOCK error is not justified will be addressed by advanced deadlock detector for MDL subsystem which we plan to implement. mysql-test/include/handler.inc: Adjusted handler_myisam.test and handler_innodb.test to the fact that exclusive metadata locks on tables are now acquired according to alphabetical order of fully qualified table names instead of order in which tables are mentioned in statement. mysql-test/r/handler_innodb.result: Adjusted handler_myisam.test and handler_innodb.test to the fact that exclusive metadata locks on tables are now acquired according to alphabetical order of fully qualified table names instead of order in which tables are mentioned in statement. mysql-test/r/handler_myisam.result: Adjusted handler_myisam.test and handler_innodb.test to the fact that exclusive metadata locks on tables are now acquired according to alphabetical order of fully qualified table names instead of order in which tables are mentioned in statement. mysql-test/r/mdl_sync.result: Adjusted mdl_sync.test to the fact that exclusive metadata locks on tables are now acquired according to alphabetical order of fully qualified table names instead of order in which tables are mentioned in statement. mysql-test/t/mdl_sync.test: Adjusted mdl_sync.test to the fact that exclusive metadata locks on tables are now acquired according to alphabetical order of fully qualified table names instead of order in which tables are mentioned in statement. sql/events.cc: Instead of using separate MDL_context for opening system tables we now create MDL savepoint in the main context before opening such tables and rollback to this savepoint after closing them. To support this change methods of THD responsible for saving/restoring open table state were changed to use Open_tables_backup class which in addition to Open_table_state has a member for this savepoint. As result code opening/closing system tables was changed to use Open_tables_backup instead of Open_table_state class as well. sql/ha_ndbcluster.cc: Since manipulations with open table state no longer install proxy MDL_context it does not make sense to perform them in order to satisfy assert in mysql_rm_tables_part2(). Removed them per agreement with Cluster team. This has not broken test suite since scenario in which deadlock can occur and assertion fails is not covered by tests. sql/lock.cc: MDL subsystem no longer implicitly acquires global intention exclusive metadata lock when per-object exclusive metadata lock is acquired. Now this has to be done by explicit calls outside of MDL subsystem. sql/log.cc: Instead of using separate MDL_context for opening system tables we now create MDL savepoint in the main context before opening such tables and rollback to this savepoint after closing them. To support this change methods of THD responsible for saving/restoring open table state were changed to use Open_tables_backup class which in addition to Open_table_state has a member for this savepoint. As result code opening/closing system tables was changed to use Open_tables_backup instead of Open_table_state class as well. sql/mdl.cc: Changed metadata locking subsystem to use mutex per lock and condition variable per context instead of one mutex and one conditional variable for the whole subsystem. Changed approach to handling of global metadata locks. Instead of implicitly acquiring intention exclusive locks when user requests per-object upgradeable or exclusive locks now we require them to be acquired explicitly in the same way as ordinary metadata locks. In fact global lock are now ordinary metadata locks in new GLOBAL namespace. To implement these changes: - Removed LOCK_mdl mutex and COND_mdl condition variable. - Introduced MDL_lock::m_mutex mutexes which protect individual lock objects. - Replaced mdl_locks hash with MDL_map class, which has hash for MDL_lock objects as a member and separate mutex which protects this hash. Methods of this class allow to find(), find_or_create() or remove() MDL_lock objects in concurrency-friendly fashion (i.e. for most common operation, find_or_create(), we don't acquire MDL_lock::m_mutex while holding MDL_map::m_mutex. Thanks to MikaelR for this idea and benchmarks!). Added three auxiliary members to MDL_lock class (m_is_destroyed, m_ref_usage, m_ref_release) to support this concurrency-friendly behavior. - Introduced MDL_context::m_ctx_wakeup_cond condition variable to be used for waiting until this context's pending request can be satisfied or its thread has to perform actions to resolve potential deadlock. Context which want to wait add ticket corresponding to the request to an appropriate queue of waiters in MDL_lock object so they can be noticed when other contexts change state of lock and be awaken by them by signalling on MDL_context::m_ctx_wakeup_cond. As consequence MDL_ticket objects has to be used for any waiting in metadata locking subsystem including one which happens in MDL_context::wait_for_locks() method. Another consequence is that MDL_context is no longer copyable and can't be saved/restored when working with system tables. - Made MDL_lock an abstract class, which delegates specifying exact compatibility matrix to its descendants. Added MDL_global_lock child class for global lock (The old is_lock_type_compatible() method became can_grant_lock() method of this class). Added MDL_object_lock class to represent per-object lock (The old MDL_lock::can_grant_lock() became its method). Choice between two classes happens based on MDL namespace in MDL_lock::create() method. - Got rid of MDL_lock::type member as its meaning became ambigous for global locks. - To simplify waking up of contexts waiting for lock split waiting queue in MDL_lock class in two queues. One for pending requests for exclusive (including intention exclusive) locks and another for requests for shared locks. - Added virtual wake_up_waiters() method to MDL_lock, MDL_global_lock and MDL_object_lock classes which allows to wake up waiting contexts after state of lock changes. Replaced old duplicated code with calls to this method. - Adjusted MDL_context::try_acquire_shared_lock()/exclusive_lock()/ global_shared_lock(), MDL_ticket::upgrade_shared_lock_to_exclusive_lock() and MDL_context::release_ticket() methods to use MDL_map and MDL_lock::m_mutex instead of single LOCK_mdl mutex and wake up waiters according to the approach described above. The latter method also was renamed to MDL_context::release_lock(). - Changed MDL_context::try_acquire_shared_lock()/exclusive_lock() and release_lock() not to handle global locks. They are now supposed to be taken explicitly like ordinary metadata locks. - Added helper MDL_context::try_acquire_global_intention_exclusive_lock() and acquire_global_intention_exclusive_lock() methods. - Moved common code from MDL_context::acquire_global_shared_lock() and acquire_global_intention_exclusive_lock() to new method - MDL_context::acquire_lock_impl(). - Moved common code from MDL_context::try_acquire_shared_lock(), try_acquire_global_intention_exclusive_lock()/exclusive_lock() to MDL_context::try_acquire_lock_impl(). - Since acquiring of several exclusive locks can no longer happen under single LOCK_mdl mutex the approach to it had to be changed. Now we do it in one by one fashion. This is done in alphabetical order to avoid deadlocks. Changed MDL_context::acquire_exclusive_locks() accordingly (as part of this change moved code responsible for acquiring single exclusive lock to new MDL_context::acquire_exclusive_lock_impl() method). - Since we no longer have single LOCK_mdl mutex which protects all MDL_context::m_is_waiting_in_mdl members using these members to determine if we have really awaken context holding conflicting shared lock became inconvinient. Got rid of this member and changed notify_shared_lock() helper function and process of acquiring of/upgrading to exclusive lock not to rely on such information. Now in MDL_context::acquire_exclusive_lock_impl() and MDL_ticket::upgrade_shared_lock_to_exclusive_lock() we simply re-try to wake up threads holding conflicting shared locks after small time out. - Adjusted MDL_context::can_wait_lead_to_deadlock() and MDL_ticket::has_pending_conflicting_lock() to use per-lock mutexes instead of LOCK_mdl. To do this introduced MDL_lock::has_pending_exclusive_lock() method. sql/mdl.h: Changed metadata locking subsystem to use mutex per lock and condition variable per context instead of one mutex and one conditional variable for the whole subsystem. In order to implement this change: - Added MDL_key::cmp() method to be able to sort MDL_key objects alphabetically. Changed length fields in MDL_key class to uint16 as 16-bit is enough for length of any key. - Changed MDL_ticket::get_ctx() to return pointer to non-const object in order to be able to use MDL_context::awake() method for such contexts. - Got rid of unlocked versions of can_wait_lead_to_deadlock()/ has_pending_conflicting_lock() methods in MDL_context and MDL_ticket. We no longer has single mutex which protects all locks. Thus one always has to use versions of these methods which acquire per-lock mutexes. - MDL_request_list type of list now counts its elements. - Added MDL_context::m_ctx_wakeup_cond condition variable to be used for waiting until this context's pending request can be satisfied or its thread has to perform actions to resolve potential deadlock. Added awake() method to wake up context from such wait. Addition of condition variable made MDL_context uncopyable. As result we no longer can save/restore MDL_context when working with system tables. Instead we create MDL savepoint before opening those tables and rollback to it once they are closed. - MDL_context::release_ticket() became release_lock() method. - Added auxiliary MDL_context::acquire_exclusive_lock_impl() method which does all necessary work to acquire exclusive lock on one object but should not be used directly as it does not enforce any asserts ensuring that no deadlocks are possible. - Since we no longer need to know if thread trying to acquire exclusive lock managed to wake up any threads having conflicting shared locks (as, anyway, we will try to wake up such threads again shortly) - MDL_context::m_is_waiting_in_mdl member became unnecessary and notify_shared_lock() no longer needs to be friend of MDL_context. Changed approach to handling of global metadata locks. Instead of implicitly acquiring intention exclusive locks when user requests per-object upgradeable or exclusive locks now we require them to be acquired explicitly in the same way as ordinary metadata locks. - Added new GLOBAL namespace for such locks. - Added new type of lock to be requested MDL_INTENTION_EXCLISIVE. - Added MDL_context::try_acquire_global_intention_exclusive_lock() and acquire_global_intention_exclusive_lock() methods. - Moved common code from MDL_context::acquire_global_shared_lock() and acquire_global_intention_exclusive_lock() to new method - MDL_context::acquire_lock_impl(). - Moved common code from MDL_context::try_acquire_shared_lock(), try_acquire_global_intention_exclusive_lock()/exclusive_lock() to MDL_context::try_acquire_lock_impl(). - Added helper MDL_context::is_global_lock_owner() method to be able easily to find what kind of global lock this context holds. - MDL_context::m_has_global_shared_lock became unnecessary as global read lock is now represented by ordinary ticket. - Removed assert in MDL_context::set_lt_or_ha_sentinel() which became false for cases when we execute LOCK TABLES under global read lock mode. sql/mysql_priv.h: Instead of using separate MDL_context for opening system tables we now create MDL savepoint in the main context before opening such tables and rollback to this savepoint after closing them. To support this change methods of THD responsible for saving/restoring open table state were changed to use Open_tables_backup class which in addition to Open_table_state has a member for this savepoint. As result calls opening/closing system tables were changed to use Open_tables_backup instead of Open_table_state class as well. sql/sp.cc: Instead of using separate MDL_context for opening system tables we now create MDL savepoint in the main context before opening such tables and rollback to this savepoint after closing them. To support this change methods of THD responsible for saving/restoring open table state were changed to use Open_tables_backup class which in addition to Open_table_state has a member for this savepoint. As result code opening/closing system tables was changed to use Open_tables_backup instead of Open_table_state class as well. sql/sp.h: Instead of using separate MDL_context for opening system tables we now create MDL savepoint in the main context before opening such tables and rollback to this savepoint after closing them. To support this change methods of THD responsible for saving/restoring open table state were changed to use Open_tables_backup class which in addition to Open_table_state has a member for this savepoint. As result code opening/closing system tables was changed to use Open_tables_backup instead of Open_table_state class as well. sql/sql_base.cc: close_thread_tables(): Since we no longer use separate MDL_context for opening system tables we need to avoid releasing all transaction locks when closing system table. Releasing metadata lock on system table is now responsibility of THD::restore_backup_open_tables_state(). open_table_get_mdl_lock(), Open_table_context::recover_from_failed_open(): MDL subsystem no longer implicitly acquires global intention exclusive metadata lock when per-object upgradable or exclusive metadata lock is acquired. So this have to be done explicitly from these calls. Changed Open_table_context class to store MDL_request object for global intention exclusive lock acquired when opening tables. open_table(): Do not release metadata lock if we have failed to open table as this lock might have been acquired by one of previous statements in transaction, and therefore should not be released. open_system_tables_for_read()/close_system_tables()/ open_performance_schema_table(): Instead of using separate MDL_context for opening system tables we now create MDL savepoint in the main context before opening such tables and rollback to this savepoint after closing them. To support this change methods of THD responsible for saving/restoring open table state were changed to use Open_tables_backup class which in addition to Open_table_state has a member for this savepoint. As result code opening/closing system tables was changed to use Open_tables_backup instead of Open_table_state class as well. close_performance_schema_table(): Got rid of duplicated code. sql/sql_class.cc: Instead of using separate MDL_context for opening system tables we now create MDL savepoint in the main context before opening such tables and rollback to this savepoint after closing them. To support this change methods of THD responsible for saving/restoring open table state were changed to use Open_tables_backup class which in addition to Open_table_state has a member for this savepoint. Also releasing metadata lock on system table is now responsibility of THD::restore_backup_open_tables_state(). Adjusted assert in THD::cleanup() to take into account fact that now we also use MDL sentinel for global read lock. sql/sql_class.h: Instead of using separate MDL_context for opening system tables we now create MDL savepoint in the main context before opening such tables and rollback to this savepoint after closing them. As result: - 'mdl_context' member was moved out of Open_tables_state to THD class. enter_locked_tables_mode()/leave_locked_tables_mode() had to follow. - Methods of THD responsible for saving/restoring open table state were changed to use Open_tables_backup class which in addition to Open_table_state has a member for this savepoint. Changed Open_table_context class to store MDL_request object for global intention exclusive lock acquired when opening tables. sql/sql_delete.cc: MDL subsystem no longer implicitly acquires global intention exclusive metadata lock when per-object exclusive metadata lock is acquired. Now this has to be done by explicit calls outside of MDL subsystem. sql/sql_help.cc: Instead of using separate MDL_context for opening system tables we now create MDL savepoint in the main context before opening such tables and rollback to this savepoint after closing them. To support this change methods of THD responsible for saving/restoring open table state were changed to use Open_tables_backup class which in addition to Open_table_state has a member for this savepoint. As result code opening/closing system tables was changed to use Open_tables_backup instead of Open_table_state class as well. sql/sql_parse.cc: Adjusted assert reload_acl_and_cache() to the fact that global read lock now takes full-blown metadata lock. sql/sql_plist.h: Added support for element counting to I_P_List list template. One can use policy classes to specify if such counting is needed or not needed for particular list. sql/sql_show.cc: Instead of using separate MDL_context for opening tables for I_S purposes we now create MDL savepoint in the main context before opening tables and rollback to this savepoint after closing them. To support this and similar change for system tables methods of THD responsible for saving/restoring open table state were changed to use Open_tables_backup class which in addition to Open_table_state has a member for this savepoint. As result code opening/closing tables for I_S purposes was changed to use Open_tables_backup instead of Open_table_state class as well. sql/sql_table.cc: mysql_rm_tables_part2(): Since now global intention exclusive metadata lock is ordinary metadata lock we no longer can rely that by releasing MDL locks on all tables we will release all locks acquired by this routine. So in non-LOCK-TABLES mode we have to release all locks acquired explicitly. prepare_for_repair(), mysql_alter_table(): MDL subsystem no longer implicitly acquires global intention exclusive metadata lock when per-object exclusive metadata lock is acquired. Now this has to be done by explicit calls outside of MDL subsystem. sql/tztime.cc: Instead of using separate MDL_context for opening system tables we now create MDL savepoint in the main context before opening such tables and rollback to this savepoint after closing them. To support this change methods of THD responsible for saving/restoring open table state were changed to use Open_tables_backup class which in addition to Open_table_state has a member for this savepoint. As result code opening/closing system tables was changed to use Open_tables_backup instead of Open_table_state class as well. Also changed code not to use special mechanism for open system tables when it is not really necessary.	2010-01-21 23:43:03 +03:00
Dmitry Lenev	0228c98936	Implementation of simple deadlock detection for metadata locks. ... This change is supposed to reduce number of ER_LOCK_DEADLOCK errors which occur when multi-statement transaction encounters conflicting metadata lock in cases when waiting is possible. The idea is not to fail ER_LOCK_DEADLOCK error immediately when we encounter conflicting metadata lock. Instead we release all metadata locks acquired by current statement and start to wait until conflicting lock go away. To avoid deadlocks we use simple empiric which aborts waiting with ER_LOCK_DEADLOCK error if it turns out that somebody is waiting for metadata locks owned by this transaction. This patch also fixes bug #46273 "MySQL 5.4.4 new MDL: Bug#989 is not fully fixed in case of ALTER". The bug was that concurrent execution of UPDATE or MULTI-UPDATE statement as a part of multi-statement transaction that already has used table being updated and ALTER TABLE statement might have resulted of loss of isolation between this transaction and ALTER TABLE statement, which manifested itself as changes performed by ALTER TABLE becoming visible in transaction and wrong binary log order as a consequence. This problem occurred when UPDATE or MULTI-UPDATE's wait in mysql_lock_tables() call was aborted due to metadata lock upgrade performed by concurrent ALTER TABLE. After such abort all metadata locks held by transaction were released but transaction silently continued to be executed as if nothing has happened. We solve this problem by changing our code not to release all locks in such case. Instead we release only locks which were acquired by current statement and then try to reacquire them by restarting open/lock tables process. We piggyback on simple deadlock detector implementation since this change has to be done anyway for it. mysql-test/include/handler.inc: After introduction of basic deadlock detector for metadata locks it became necessary to change parts of test for HANDLER statements which covered some of scenarios in which ER_LOCK_DEADLOCK error was detected in absence of real deadlock (with new deadlock detector this no longer happens). Also adjusted test to the fact that HANDLER READ for the table no longer will be blocked by ALTER TABLE for the same table which awaits for metadata lock upgrade (this is due to removal of mysql_lock_abort() from wait_while_table_is_used()). mysql-test/r/handler_innodb.result: After introduction of basic deadlock detector for metadata locks it became necessary to change parts of test for HANDLER statements which covered some of scenarios in which ER_LOCK_DEADLOCK error was detected in absence of real deadlock (with new deadlock detector this no longer happens). Also adjusted test to the fact that HANDLER READ for the table no longer will be blocked by ALTER TABLE for the same table which awaits for metadata lock upgrade (this is due to removal of mysql_lock_abort() from wait_while_table_is_used()). mysql-test/r/handler_myisam.result: After introduction of basic deadlock detector for metadata locks it became necessary to change parts of test for HANDLER statements which covered some of scenarios in which ER_LOCK_DEADLOCK error was detected in absence of real deadlock (with new deadlock detector this no longer happens). Also adjusted test to the fact that HANDLER READ for the table no longer will be blocked by ALTER TABLE for the same table which awaits for metadata lock upgrade (this is due to removal of mysql_lock_abort() from wait_while_table_is_used()). mysql-test/r/mdl_sync.result: Added test coverage for basic deadlock detection in metadata locking subsystem and for bug #46273 "MySQL 5.4.4 new MDL: Bug#989 is not fully fixed in case of ALTER". mysql-test/r/sp-lock.result: Adjusted test coverage for metadata locking for stored routines since after introduction of basic deadlock detector for metadata locks number of scenarios in which ER_LOCK_DEADLOCK error in absence of deadlock has decreased. mysql-test/t/mdl_sync.test: Added test coverage for basic deadlock detection in metadata locking subsystem and for bug #46273 "MySQL 5.4.4 new MDL: Bug#989 is not fully fixed in case of ALTER". mysql-test/t/sp-lock.test: Adjusted test coverage for metadata locking for stored routines since after introduction of basic deadlock detector for metadata locks number of scenarios in which ER_LOCK_DEADLOCK error in absence of deadlock has decreased. sql/log_event_old.cc: close_tables_for_reopen() now takes one more argument which specifies at which point it should stop releasing metadata locks acquired by this connection. sql/mdl.cc: Changed metadata locking subsystem to support basic deadlock detection with a help of the following simple empiric -- we assume that there is a deadlock if there is a connection which has to wait for a metadata lock which is currently acquired by some connection which is itself waiting to be able to acquire some shared metadata lock. To implement this change: - Added MDL_context::can_wait_lead_to_deadlock()/_impl() methods which allow to find out if there is someone waiting for metadata lock which is held by the connection and therefore deadlocks are possible if this connection is going to wait for some metadata lock. To do this added version of MDL_ticket::has_pending_conflicting_lock() method which assumes that its caller already owns LOCK_mdl mutex. - Changed MDL_context::wait_for_locks() to use one of the above methods to check if somebody is waiting for metadata lock owned by this context (and therefore deadlock is possible) and emit ER_LOCK_DEADLOCK error in this case. Also now we mark context of connections waiting inside of this method by setting MDL_context::m_is_waiting_in_mdl member. Thanks to this such connection could be waken up if some other connection starts waiting for one of its metadata locks and so a deadlock can occur. - Adjusted notify_shared_lock() to wake up connections which wait inside MDL_context::wait_for_locks() while holding shared metadata lock. - Changed MDL_ticket::upgrade_shared_lock_to_exclusive() to add temporary ticket for exclusive lock to MDL_lock::waiting queue, so request for metadata lock upgrade can be properly detected by our empiric. Also now this method invokes a callback which forces transactions holding shared metadata lock on the table to call MDL_context:: can_wait_lead_to_deadlock() method even if they don't need any new metadata locks. Thanks to this such transactions can detect deadlocks/ livelocks between MDL and table-level locks. Also reduced timeouts between calls to notify_shared_lock() in MDL_ticket::upgrade_shared_lock_to_exclusive() and MDL_context::acquire_exclusive_locks(). This was necessary to get rid of call to mysql_lock_abort() in wait_while_table_is_used(). (Now we instead rely on notify_shared_lock() timely calling mysql_lock_abort_for_thread() for the table on which lock is being upgraded/acquired). sql/mdl.h: - Added a version of MDL_ticket::has_pending_conflicting_lock() method to be used in situations when caller already has acquired LOCK_mdl mutex. - Added MDL_context::can_wait_lead_to_deadlock()/_impl() methods which allow to find out if there is someone waiting for metadata lock which is held by this connection and thus deadlocks are possible if this connections will start waiting for some metadata lock. - Added MDL_context::m_is_waiting_in_mdl member to mark connections waiting in MDL_context::wait_for_locks() method of metadata locking subsystem. Added getter method for this private member to make it accessible in notify_shared_lock() auxiliary so we can wake-up such connections if they hold shared metadata locks. - Finally, added mysql_abort_transactions_with_shared_lock() callback to be able force transactions which don't need any new metadata locks still call MDL_context::can_wait_lead_to_deadlock() and detect some of deadlocks between metadata locks and table-level locks. sql/mysql_priv.h: close_tables_for_reopen() now takes one more argument which specifies at which point it should stop releasing metadata locks acquired by this connection. sql/sql_base.cc: Changed approach to metadata locking for multi-statement transactions. We no longer fail ER_LOCK_DEADLOCK error immediately when we encounter conflicting metadata lock. Instead we release all metadata locks acquired by current statement and start to wait until conflicting locks to go away by calling MDL_context::wait_for_locks() method. To avoid deadlocks the latter implements simple empiric which aborts waiting with ER_LOCK_DEADLOCK error if it turns out that somebody is waiting for metadata locks owned by this transaction. To implement the change described above: - Introduced Open_table_context::m_start_of_statement_svp member to store state of metadata locks at the start of the statement. - Changed Open_table_context::request_backoff_action() not to fail with ER_LOCK_DEADLOCK immediately if back-off is requested due to conflicting metadata lock. - Added new argument for close_tables_for_reopen() procedure which allows to specify subset of metadata locks to be released. - Changed open_tables() not to release all metadata locks acquired by current transaction when metadata lock conflict is discovered. Instead we release only locks acquired by current statement. - Changed open_ltable() and open_and_lock_tables_derived() not to emit ER_LOCK_DEADLOCK error when mysql_lock_tables() is aborted in multi-statement transaction when somebody tries to acquire exclusive metadata lock on the table. Instead we release metadata locks acquired by current statement and try to wait until they can be re-acquired. - Adjusted tdc_wait_for_old_versions() to check if there is someone waiting for one of metadata locks held by this connection and run deadlock detection in order to avoid deadlocks in some situations. - Added mysql_abort_transactions_with_shared_lock() callback which allows to force transactions holding shared metadata lock on the table to call MDL_context::can_wait_lead_to_deadlock() even if they don't need any new metadata locks so they can detect potential deadlocks between metadata locking subsystem and table-level locks. - Adjusted wait_while_table_is_used() not to set TABLE::version to 0 as it is now done only when necessary by the above-mentioned callback. Also removed unnecessary call to mysql_lock_abort(). Instead we rely on code performing metadata lock upgrade aborting waits on the table-level lock for this table by calling mysql_lock_abort_for_thread() (invoked by mysql_notify_thread_having_shared_lock()). In future this should allow to reduce number of scenarios in which we produce ER_LOCK_DEADLOCK error even though no real deadlock exists. sql/sql_class.h: Introduced Open_table_context::m_start_of_statement_svp member to store state of metadata locks at the start of the statement. Replaced Open_table_context::m_can_deadlock member with m_has_locks member to reflect the fact that we no longer unconditionally emit ER_LOCK_DEADLOCK error for transaction having some metadata locks when conflicting metadata lock is discovered. sql/sql_insert.cc: close_tables_for_reopen() now takes one more argument which specifies at which point it should stop releasing metadata locks acquired by this connection. sql/sql_plist.h: Made I_P_List_iterator<T, B> usable with const lists. sql/sql_show.cc: close_tables_for_reopen() now takes one more argument which specifies at which point it should stop releasing metadata locks acquired by this connection. sql/sql_update.cc: Changed UPDATE and MULTI-UPDATE code not to release all metadata locks when calls to mysql_lock_tables() are aborted. Instead we release only locks which are acquired by this statement and then try to reacquire them by calling open_tables(). This solves bug #46273 "MySQL 5.4.4 new MDL: Bug#989 is not fully fixed in case of ALTER".	2009-12-30 20:53:30 +03:00
Jon Olav Hauglid	94154c9592	Backport of revno: 3690 ... Postfix for Bug#48210 FLUSH TABLES WITH READ LOCK deadlocks against concurrent CREATE PROCEDURE Rewrote the second test to use DROP PROCEDURE instead of CREATE USER as CREATE USER does not work with embedded server.	2009-12-10 15:09:56 +01:00
Jon Olav Hauglid	3d062adf25	Backport of revno: 3685 ... Bug #48210 FLUSH TABLES WITH READ LOCK deadlocks against concurrent CREATE PROCEDURE This deadlock occured between a) CREATE PROCEDURE (or other commands listed below) b) FLUSH TABLES WITH READ LOCK If the execution of them happened in the following order: - a) opens a table (e.g. mysql.proc) - b) locks the global read lock (or GRL) - a) sleeps inside wait_if_global_read_lock() - b) increases refresh_version and sleeps waiting for old tables to go away Note that a) must start waiting on the GRL before FLUSH increases refresh_version. Otherwise a) won't wait on the GRL and instead close its tables for reopen, allowing FLUSH to complete and thus avoid the deadlock. With this patch the deadlock is avoided by making CREATE PROCEDURE acquire a protection against global read locks before it starts executing. This means that FLUSH TABLES WITH READ LOCK will have to wait until CREATE PROCEDURE completes before acquiring the global read lock, thereby avoiding the deadlock. This is implemented by introducing a new SQL command flag called CF_PROTECT_AGAINST_GRL. Commands marked with this flag will acquire a GRL protection in the beginning of mysql_execute_command(). This patch adds the flag to CREATE, ALTER and DROP for PROCEDURE and FUNCTION, as well as CREATE USER, DROP USER, RENAME USER and REVOKE ALL. All these commands either call open_grant_tables() or open_system_table_for_updated() which make them susceptible for this deadlock. The patch also adds the CF_PROTECT_AGAINST_GRL flag to a number of commands that previously acquired GRL protection in their respective SQLCOM case in mysql_execute_command(). Test case that checks for GRL protection for CREATE PROCEDURE and CREATE USER added to mdl_sync.test.	2009-12-10 15:09:00 +01:00
Jon Olav Hauglid	5e1dfa4c06	Backport of revno: 2617.71.1 ... Bug#42546 Backup: RESTORE fails, thinking it finds an existing table The problem occured when a MDL locking conflict happened for a non-existent table between a CREATE and a INSERT statement. The code for CREATE interpreted this lock conflict to mean that the table existed, which meant that the statement failed when it should not have. The problem could occur for CREATE TABLE, CREATE TABLE LIKE and ALTER TABLE RENAME. This patch fixes the problem for CREATE TABLE and CREATE TABLE LIKE. It is based on code backported from the mysql-6.1-fk tree written by Dmitry Lenev. CREATE now uses normal open_and_lock_tables() code to acquire exclusive locks. This means that for the test case in the bug description, CREATE will wait until INSERT completes so that it can get the exclusive lock. This resolves the reported bug. The patch also prohibits CREATE TABLE and CREATE TABLE LIKE under LOCK TABLES. Note that this is an incompatible change and must be reflected in the documentation. Affected test cases have been updated. mdl_sync.test contains tests for CREATE TABLE and CREATE TABLE LIKE. Fixing the issue for ALTER TABLE RENAME is beyond the scope of this patch. ALTER TABLE cannot be prohibited from working under LOCK TABLES as this could seriously impact customers and a proper fix would require a significant rewrite.	2009-12-10 11:53:20 +01:00
Konstantin Osipov	e001a9f0d0	Backport of: ... ------------------------------------------------------------ revno: 2617.68.10 committer: Dmitry Lenev <dlenev@mysql.com> branch nick: mysql-next-bg46673 timestamp: Tue 2009-09-01 19:57:05 +0400 message: Fix for bug #46673 "Deadlock between FLUSH TABLES WITH READ LOCK and DML". Deadlocks occured when one concurrently executed transactions with several statements modifying data and FLUSH TABLES WITH READ LOCK statement or SET READ_ONLY=1 statement. These deadlocks were introduced by the patch for WL 4284: "Transactional DDL locking"/Bug 989: "If DROP TABLE while there's an active transaction, wrong binlog order" which has changed FLUSH TABLES WITH READ LOCK/SET READ_ONLY=1 to wait for pending transactions. What happened was that FLUSH TABLES WITH READ LOCK blocked all further statements changing tables by setting global_read_lock global variable and has started waiting for all pending transactions to complete. Then one of those transactions tried to executed DML, detected that global_read_lock non-zero and tried to wait until global read lock will be released (i.e. global_read_lock becomes 0), indeed, this led to a deadlock. Proper solution for this problem should probably involve full integration of global read lock with metadata locking subsystem (which will allow to implement waiting for pending transactions without blocking DML in them). But since it requires significant changes another, short-term solution for the problem is implemented in this patch. Basically, this patch restores behavior of FLUSH TABLES WITH READ LOCK/ SET READ_ONLY=1 before the patch for WL 4284/bug 989. By ensuring that extra references to TABLE_SHARE are not stored for active metadata locks it changes these statements not to wait for pending transactions. As result deadlock is eliminated. Note that this does not change the fact that active FLUSH TABLES WITH READ LOCK lock or SET READ_ONLY=1 prevent modifications to tables as they also block transaction commits. mysql-test/r/flush_block_commit.result: Adjusted test case after change in FLUSH TABLES WITH READ LOCK behavior - it is no longer blocked by a pending transaction. mysql-test/r/mdl_sync.result: Added test for bug #46673 "Deadlock between FLUSH TABLES WITH READ LOCK and DML". mysql-test/r/read_only_innodb.result: Adjusted test case after change in SET READ_ONLY behavior - it is no longer blocked by a pending transaction. mysql-test/t/flush_block_commit.test: Adjusted test case after change in FLUSH TABLES WITH READ LOCK behavior - it is no longer blocked by a pending transaction. mysql-test/t/mdl_sync.test: Added test for bug #46673 "Deadlock between FLUSH TABLES WITH READ LOCK and DML". mysql-test/t/read_only_innodb.test: Adjusted test case after change in SET READ_ONLY behavior - it is no longer blocked by a pending transaction. sql/sql_base.cc: Disable caching of pointers to TABLE_SHARE objects in MDL subsystem. This means that transactions holding metadata lock on the table will no longer have extra reference to the TABLE_SHARE (due to this lock) and will no longer block concurrent FLUSH TABLES/FLUSH TABLES WITH READ LOCK. Note that this does not change the fact that FLUSH TABLES WITH READ LOCK prevents concurrent transactions from modifying data as it also blocks all commits.	2009-12-09 18:56:34 +03:00
Konstantin Osipov	2f26574026	Backport of: ... ------------------------------------------------------------ revno: 2617.68.7 committer: Dmitry Lenev <dlenev@mysql.com> branch nick: mysql-next-bg46044 timestamp: Thu 2009-08-27 10:22:17 +0400 message: Fix for bug #46044 "MDL deadlock on LOCK TABLE + CREATE TABLE HIGH_PRIORITY FOR UPDATE". Deadlock occured when during execution of query to I_S we tried to open a table or its .FRM in order to get information about it and had to wait because we have encountered exclusive metadata lock on this table held by a DDL operation from another connection which in its turn waited for some resource currently owned by connection executing this I_S query. For example, this might have happened if one under LOCK TABLES executed I_S query targeted to particular table (which was not among locked) and also concurrently tried to create this table using CREATE TABLE SELECT which had to wait for one of tables locked by the first connection. Another situation in which deadlock might have occured is when I_S query, which was executed as part of transaction, tried to get information about table which just has been dropped by concurrent DROP TABLES executed under LOCK TABLES and this DROP TABLES for its completion also had to wait transaction from the first connection. This problem stemmed from the fact that opening of tables/.FRMs for I_S filling is happening outside of connection's main MDL_context so code which tries to detect deadlocks due to conflicting metadata locks doesn't work in this case. Indeed, this led to deadlocks when during I_S filling we tried to wait for conflicting metadata lock to go away, while its owner was waiting for some resource held by connection executing I_S query. This patch solves this problem by avoiding waiting in such situation. Instead we skip this table and produce warning that information about it was omitted from I_S due to concurrent DDL operation. We still wait for conflicting metadata lock to go away when it is known that deadlock is not possible (i.e. when connection executing I_S query does not hold any metadata or table-level locks). Basically, we apply our standard deadlock avoidance technique for metadata locks to the process of filling of I_S tables but replace ER_LOCK_DEADLOCK error with a warning. Note that this change is supposed to be safe for 'mysqldump' since the only its mode which is affected by this change is --single-transaction mode is not safe in the presence of concurrent DDL anyway (and this fact is documented). Other modes are unaffected because they either use SHOW TABLES/SELECT * FROM I_S.TABLE_NAMES which do not take any metadata locks in the process of I_S table filling and thus cannot skip tables or execute I_S queries for tables which were previously locked by LOCK TABLES (or in the presence of global read lock) which excludes possibility of encountering conflicting metadata lock. mysql-test/r/mdl_sync.result: Added test for bug #46044 "MDL deadlock on LOCK TABLE + CREATE TABLE HIGH_PRIORITY FOR UPDATE". mysql-test/t/mdl_sync.test: Added test for bug #46044 "MDL deadlock on LOCK TABLE + CREATE TABLE HIGH_PRIORITY FOR UPDATE". sql/mysql_priv.h: Added a new flag for open_table() call which allows it to fail with an error in cases when conflicting metadata lock is discovered instead of waiting until this lock goes away. sql/share/errmsg-utf8.txt: Added error/warning message to be generated in cases when information about table is omitted from I_S since there is conflicting metadata lock on the table. sql/share/errmsg.txt: Added error/warning message to be generated in cases when information about table is omitted from I_S since there is conflicting metadata lock on the table. sql/sql_base.cc: Added a new flag for open_table() call which allows it to fail with an error in cases when conflicting metadata lock is discovered instead of waiting until this lock goes away. sql/sql_show.cc: When we are opening a table (or just .FRM) in order to fill I_S with information about this table and encounter conflicting metadata lock waiting for this lock to go away can lead to a deadlock in some situations (under LOCK TABLES, within transaction, etc.). To avoid these deadlocks we detect such situations and don't do waiting. Instead, we skip table for which we have conflicting metadata lock, thus omitting information about it from I_S table, and produce an appropriate warning.	2009-12-09 18:48:42 +03:00
Konstantin Osipov	736db89a76	Backport of: ... ------------------------------------------------------------ revno: 2617.69.37 committer: Dmitry Lenev <dlenev@mysql.com> branch nick: mysql-next-bg46748 timestamp: Fri 2009-08-21 18:17:02 +0400 message: Fix for bug #46748 "Assertion in MDL_context::wait_for_locks() on INSERT + CREATE TRIGGER". Concurrent execution of statements involving stored functions or triggers which were using several tables and DDL statements which affected those tables on debug build of server might have led to assertion failures in MDL_context::wait_for_locks(). Non-debug build was not affected. The problem was that during back-off which happens when open_tables() encounters conflicting metadata lock for one of the tables being open we didn't reset MDL_request::ticket value for requests which correspond to tables from extended prelocking set. Since these requests are part of of list of requests to be waited for in Open_table_context this broke assumption that ticket value for them is 0 in MDL_context::wait_for_locks() and caused assertion failure. This fix ensures that close_tables_for_reopen(), which performs this back-off resets MDL_request::ticket value not only for tables directly used by the statement but also for tables from extended prelocking set, thus satisfying assumption described above. mysql-test/r/mdl_sync.result: Added test case for bug #46748 "Assertion in MDL_context::wait_for_locks() on INSERT + CREATE TRIGGER". mysql-test/t/mdl_sync.test: Added test case for bug #46748 "Assertion in MDL_context::wait_for_locks() on INSERT + CREATE TRIGGER". sql/sql_base.cc: Since metadata lock requests for tables from extended part of prelocking set are also part of list of requests to be waited for in Open_table_context in close_tables_for_reopen() we have to reset MDL_request::ticket values for them to assumptions in MDL_context::wait_for_locks().	2009-12-09 12:44:05 +03:00
Konstantin Osipov	f477e66ec5	Backport of: ... ------------------------------------------------------------ revno: 2617.23.18 committer: Davi Arnaut <Davi.Arnaut@Sun.COM> branch nick: 4284-6.0 timestamp: Mon 2009-03-02 18:18:26 -0300 message: Bug#989: If DROP TABLE while there's an active transaction, wrong binlog order WL#4284: Transactional DDL locking This is a prerequisite patch: These changes are intended to split lock requests from granted locks and to allow the memory and lifetime of granted locks to be managed within the MDL subsystem. Furthermore, tickets can now be shared and therefore are used to satisfy multiple lock requests, but only shared locks can be recursive. The problem is that the MDL subsystem morphs lock requests into granted locks locks but does not manage the memory and lifetime of lock requests, and hence, does not manage the memory of granted locks either. This can be problematic because it puts the burden of tracking references on the users of the subsystem and it can't be easily done in transactional contexts where the locks have to be kept around for the duration of a transaction. Another issue is that recursive locks (when the context trying to acquire a lock already holds a lock on the same object) requires that each time the lock is granted, a unique lock request/granted lock structure structure must be kept around until the lock is released. This can lead to memory leaks in transactional contexts as locks taken during the transaction should only be released at the end of the transaction. This also leads to unnecessary wake ups (broadcasts) in the MDL subsystem if the context still holds a equivalent of the lock being released. These issues are exacerbated due to the fact that WL#4284 low-level design says that the implementation should "2) Store metadata locks in transaction memory root, rather than statement memory root" but this is not possible because a memory root, as implemented in mysys, requires all objects allocated from it to be freed all at once. This patch combines review input and significant code contributions from Konstantin Osipov (kostja) and Dmitri Lenev (dlenev). mysql-test/r/mdl_sync.result: Add test case result. mysql-test/t/mdl_sync.test: Add test case for shared lock upgrade case. sql/event_db_repository.cc: Rename mdl_alloc_lock to mdl_request_alloc. sql/ha_ndbcluster_binlog.cc: Use new function names to initialize MDL lock requests. sql/lock.cc: Rename MDL functions. sql/log_event.cc: The MDL request now holds the table and database name data (MDL_KEY). sql/mdl.cc: Move the MDL key to the MDL_LOCK structure in order to make the object suitable for allocation from a fixed-size allocator. This allows the simplification of the lists in the MDL_LOCK object, which now are just two, one for granted tickets and other for waiting (upgraders) tickets. Recursive requests for a shared lock on the same object can now be granted using the same lock ticket. This schema is only used for shared locks because that the only case that matters. This is used to avoid waste of resources in case a context (connection) already holds a shared lock on a object. sql/mdl.h: Introduce a metadata lock object key which is used to uniquely identify lock objects. Separate the structure used to represent pending lock requests from the structure used to represent granted metadata locks. Rename functions used to manipulate locks requests in order to have a more consistent function naming schema. sql/sp_head.cc: Rename mdl_alloc_lock to mdl_request_alloc. sql/sql_acl.cc: Rename alloc_mdl_locks to alloc_mdl_requests. sql/sql_base.cc: Various changes to accommodate that lock requests are separated from lock tickets (granted locks). sql/sql_class.h: Last acquired lock before the savepoint was set. sql/sql_delete.cc: Various changes to accommodate that lock requests are separated from lock tickets (granted locks). sql/sql_handler.cc: Various changes to accommodate that lock requests are separated from lock tickets (granted locks). sql/sql_insert.cc: Rename alloc_mdl_locks to alloc_mdl_requests. sql/sql_parse.cc: Rename alloc_mdl_locks to alloc_mdl_requests. sql/sql_plist.h: Typedef for iterator type. sql/sql_plugin.cc: Rename alloc_mdl_locks to alloc_mdl_requests. sql/sql_servers.cc: Rename alloc_mdl_locks to alloc_mdl_requests. sql/sql_show.cc: Various changes to accommodate that lock requests are separated from lock tickets (granted locks). sql/sql_table.cc: Various changes to accommodate that lock requests are separated from lock tickets (granted locks). sql/sql_trigger.cc: Save reference to the lock ticket so it can be downgraded later. sql/sql_udf.cc: Rename alloc_mdl_locks to alloc_mdl_requests. sql/table.cc: Rename mdl_alloc_lock to mdl_request_alloc. sql/table.h: Separate MDL lock requests from lock tickets (granted locks). storage/myisammrg/ha_myisammrg.cc: Rename alloc_mdl_locks to alloc_mdl_requests.	2009-12-04 02:29:40 +03:00