Mysql metadata lock timeout ** once it is forever waiting on the metadata lock, i can stop the application, which drops all connections. The permissible values range from 1 to 31536000 (1 year). SET innodb_lock_wait_timeout = 120; The default timeout for a query waiting on a metadata lock is based on the value of the lock_wait_timeout parameter, which defaults to 31,536,000 seconds (365 days). 14, this setting is not suitable for file systems such as XFS and EXT4, which require an fsync() system call to synchronize file system metadata changes. 执行DDL语句时卡住 提示 发现更改表名的进程卡住，出现表锁，之后所有对这张表的操作都会卡住 GET_LOCK(str,timeout) Tries to obtain a lock with a name given by the string str, using a timeout of timeout seconds. 为了减少 metadata lock 带来的危害，设置一个合理的 lock_wait_timeout 比较重要，这个值默认是 365 天，我们可以根据自身业务来考虑，避免长时间的 metadata lock 等待。 Nov 20, 2010 · Renamed open_and_lock_tables_derived() to open_and_lock_tables(). waiting for table level lock. 7. The default A lock wait timeout causes InnoDB to roll back the current statement (the statement that was waiting for the lock and encountered the timeout). Nov 13, 2015 · Description: Situation: CREATE TRIGGER on a busy table (w/ many writes) This hangs To troubleshoot: select LOCK_TYPE, LOCK_DURATION, LOCK_STATUS, OWNER_THREAD_ID, t. May 6, 2015 · The correct answer is the lock_wait_timeout system variable. 3版本之前,MySQL事务对于表结构元数据(Metadata)的锁定是语句(statement)粒度的即语句执行完成后，不管事务是否可以完成，其表结构就 Apr 24, 2021 · Background. While held by one session, other sessions cannot obtain a lock of the same name. In the case of MySQL, these resources can be tables, rows, or internal data structures. Jul 24, 2014 · I am using a MySQL 5. I 2nd this. 3版本中引入了Metadata lock: DDL语句打破了事务的隔离级别 在5. Mar 26, 2025 · The most important thing to remember is that the “Lock wait timeout exceeded” error happens when a transaction is waiting for a lock acquired by another. Changes that you make are immediately applied. METADATA_LOCKS A INNER JOIN PERFORMANCE_SCHEMA. , via FOR UPDATE or by using an UPDATE or DELETE > operation. lock_wait_timeout This variable specifies the timeout in seconds for attempts to acquire metadata locks. PROCESSLIST_COMMAND, t. If you cannot restart mysql at this time, run this: SET GLOBAL innodb_lock_wait_timeout = 120; You could also just set it for the duration of your session. It's a metadata lock, which uses a different timeout option, lock_wait_timeout. Metadata locking applies not just to tables, but also to schemas, stored programs (procedures, functions, triggers, scheduled events), tablespaces, user locks acquired with the GET_LOCK() function (see Section 14. Mar 12, 2023 · 所以，如果要降低metadata lock的锁等待时间，最好要及时提交事务，同时尽量避免大事务。 那么如果发生metadata lock锁等待，等待锁的session会等待多长时间呢？大家都知道MySQL里面行锁等待有个超时时间（参数innodb_lock_wait_timeout），默认50s。 May 19, 2016 · TRUNCATE TABLE is sort of a hybrid of DDL and DML in MySQL, and happens outside the scope of InnoDB's MVCC, so it can't be done with any read snapshot referencing the table -- the snapshot would be useless, hence a metadata lock. The type of lock used in the metadata lock subsystem. Metadata Dead locks may equally happen between a ddl operation on a given table (drop, alter) and a select query on that table. mysql 使用元数据锁定来管理对数据库对象的并发访问并确保数据一致性；参见 第 8. Jun 3, 2012 · I'm adding further information since I came up with another interesting experience. This function cannot be called while holding LOCK_open_mutex. mysql> truncate table mytable; <hangs> What it's waiting for is a metadata lock. May 14, 2020 · [MariaDB][ADMIN] Lock wait timeout exceeded; try restarting transaction 장애 원인 및 처리 방법 2020. > Second, the "open transaction" referenced here is not a commit-able transaction because > it did not lock anything explicitly, e. Even a "Metadata lock timeout" would be a nice future feature. Bug 61935 was not a bug, and is littered with nonsense commentary. 5, the hot topic these days is MySQL 5. lock_timeout: An integer number of seconds to wait to acquire the locks before giving up. 11. Aug 17, 2023 · 查看 State 列是否存在大量 Waiting for table metadata lock，出现 Waiting for table metadata lock 即表示出现阻塞。 查找造成阻塞的会话 ID。 查看状态为 Waiting for table metadata lock 会话的 Info 列，找到该会话操作的表，例如 sbtest2 。 Nov 7, 2023 · 实际上，MySQL也提供了一个类似的视图来解决metadata lock问题，视图名称为sys. 保留中のロックリクエスト (er_lock_wait_timeout) がタイムアウトすると、その行ステータスが pending から timeout に更新されます。 ロックまたは保留中のロックリクエストが強制終了されると、その行ステータスが GRANTED または PENDING から KILLED に更新されます。 Feb 3, 2021 · 本人博客原地址：MYSQL 持续踩坑之-metadata lock 创作时间： 2019. 05. 14, “Locking Functions”), and locks acquired with the locking service Oct 2, 2024 · Mysql2::Error::TimeoutError: Lock wait timeout exceeded という文言から、MySQL上でロックを取っている他のクエリにブロックされ、そのブロックが長時間に渡ったため自クエリがタイムアウトしてabortしてしまっているという状況のようです。 mysql_lock_remove (THD *thd, MYSQL_LOCK *locked, TABLE *table) Try to find the table in the list of locked tables. -- "Waiting for table metadata lock" <= mysql2 innodb_lock_wait_timeout 옵션으로 Sep 16, 2022 · So if there is a metadata lock lock waiting, how long will the session waiting for the lock wait? Everyone knows that there is a timeout for row lock waiting in MySQL (parameter innodb_lock_wait_timeout), the default is 50s. pid in the data directory and writes SHOW ENGINE INNODB STATUS output to it every 15 seconds, approximately. OWNER_THREAD_ID = B. Jan 19, 2018 · 在5. . 03. 3版本之前,MySQL事务对于表结构元数据(Metadata)的锁定是语句(statement)粒度的 &nb Mar 22, 2020 · 2. 3, “The metadata_locks Table” . 事前知識 1-1. Mar 8, 2024 · 文章浏览阅读2. 起因. 二、关于Table Metadata Lock 1、为什么会有 Metadata Lock 1. 还是先看官方文档，从文档上来看wait_timeout和interactive_timeout都是指不活跃的连接超时时间，连接线程启动的时候wait_timeout会根据是交互模式还是非交互模式被设置为这两个值中的一个。 The world's most popular open source database Contact MySQL | Login | Register. 1 OBJECT_TYPE. See Section 17. This table also contains one row describing each May 3, 2025 · 운영상 체크리스트 select * from information_schema. Mar 14, 2023 · 如何解决mysql 删表卡住的问题mysql删表卡住的解决办法：首先执行“show full processlist;”语句；然后执行“kill processid;”语句；最后使用kill语句将所有的id杀死，并重启MySQL即可。推荐：《mysql视频教程》MySQL表不能修改、删除等操作，卡死、锁死情况的处理办法。 Sep 20, 2018 · MySQL在进行一些alter table等DDL操作时，如果该表上有未提交的事务则会出现 Waiting for table metadata lock ，而一旦出现metadata lock，该表上的后续操作都会被阻塞，由于当时直接把ALTER给kill了，所以基本没有现场. thread_id left join events_statements_current e on e. Added MYSQL_LOCK_IGNORE_TIMEOUT flag which is used when opening and locking a table to use 1 year timeouts rather than the user- supplied timeout value (lock_wait_timeout). 2, “Deadlock Detection”. 2. 28 MySQL Community Server - GPLDBに Sakila Sample Database を利用Sakila Sample DatabaseはMySQL開発チームが提供しているMySQLの機能を検証したりするためのサンプルデータベースです… If a transaction is waiting for a lock, it is in a LOCK WAIT state. For information about the naming conventions used in MySQL wait events, see Performance Schema instrument naming conventions in the MySQL documentation. A negative timeout value means infinite timeout. 3版本之前,MySQL事务对于表结构元数据(Metadata)的锁定是语句(statement)粒度的即语句执行完成后，不管事务是否可以完成，其表结构就 Nov 11, 2024 · Why Do You See the “Lock Wait Timeout Exceeded” Error? Common Solutions to Fix the Lock Wait Timeout Issue. Another concept to get used to is the lock mode. metadata_locks is operated on connection 3 when query of connection 2 is blocking by DDL, which is described in section "How to repeat": ----- while 'select for update' is executing, operate session 3: [session 3] ysql> select NOW(); select OBJECT_TYPE,OBJECT_SCHEMA,OBJECT_NAME,LOCK_TYPE,LOCK_DURATION,LOCK_STATUS,OWNER_THREAD_ID from performance_schema OBJECT_TYPE. 04. MySQL在进行alter table等DDL操作时，有时会出现Waiting for table metadata lock的等待场景。而且，一旦alter table TableA的操作停滞在Waiting for table metadata lock的状态，后续对TableA的任何操作（包括读）都无法进行，因为他们也会在Opening tables的阶段进入到Waiting for table metadata lock的锁等待队列。 GET_LOCK(str,timeout) Tries to obtain a lock with a name given by the string str, using a timeout of timeout seconds. Mar 26, 2025 · A lock is a special object that controls access to a resource. It isn't a good idea to increase the innodb_lock_wait_timeout variable. For details, see Section 29. MySQL数据库的配置参数中有一些与Metadata Lock有关的参数，如innodb_lock_wait_timeout。你可以调整这些参数来增加Metadata Lock的等待时间，以允许长时间 Clarification: innodb_lock_wait_timeout sets the number of seconds that a transaction will wait for a lock to be released before giving up; what I want is a way of forcing a lock to be released. # MySQL `lock_wait_timeout` 参数优化指南在MySQL数据库中，`lock_wait_timeout` 参数用于定义一个线程在等待锁释放时的超时时间。当遇到锁争用时，如果一个线程在等待锁的过程中超出了这个时间，MySQL将会返回错误，提示用户等待超时。 Apr 14, 2022 · 我们码农平时大多数时间都在撸码或者撸码的路上，很少关注mysql的一些底层原理，当出现问题时没能力第一时间解决问题，出现问题后不去层层剖析问题产生的原因，后续也就可能无法避免或者绕开同类的问题。因此不要单纯做Ctrl+c和Ctrl+V，而是一边仰望星空(目标规划)，一边脚踏实地去分析每个 Jun 20, 2017 · 在 mysql 的服务器配置中, 我们经常会使用到几个 timeout诸如 connect_timeout, wait_timeout, interactive_timeout, read_timeout, write_timeout 等等我们 这里来看一下 他们的具体的使用场景, 以及具体控制的相关信息 是什么这个是 客户端 和 服务器建立连接之后, 客户端需要向服务器发起认证请求如果在 connect_timeout 期限 . It does not hang forever, there is a timeout. PROCESSLIST_USER, t. 26 [MariaDB][ADMIN] show processlist - Waiting for table metadata lock 2017. The default innodb_lock_wait_timeout variable value is 50 seconds, but you can check it with this query: SHOW VARIABLES WHERE variable_name = 'innodb_lock_wait_timeout'; Sep 27, 2024 · Bug #116145 [Warning] [MY-015116] [Server] Background histogram update on SCHEMA. 普段意識することや、使ったことが多いのは、InnoDBロックの方かなと思います。 つまり、グローバル設定上はinnodb_lock_wait_timeoutが50秒ってこと。 注意：lock_wait_timeoutという設定でもあるが、そっちはmetadata lockに使用されています。innodb_lock_wait_timeoutが正しいです。 Sep 23, 2014 · In the example, the only threads *not* in 'Waiting for table metadata lock' are: Thread 3 (executing) is using tables t2 t8 t9 t17 t27 t22 Thread 6 (Sending data) is using tables t1 t5 t7 t16 t18 t25 t29 Thread 29 (Sending data) is using tables t1 t7 t3 t10 t18 t21 t23 Yet, for instance thread 13 is 'Waiting for table metadata lock' while the table it is accessing (t6) is not in use by any of Aug 28, 2024 · 前提MySQL versionServer version: 8. cc Added timeout value to Open_table_context. 在使用mysql的时候，我们有时会碰到Waiting for table metadata lock的锁等待。但是这个锁等待比较特殊，在innodb_lock_wait和show engine innodb status 表里面都查不到。 This function cannot be called while holding LOCK_open_mutex. 68 before timing out? May 5, 2016 · There are various solutions to tackling MDL: Appropriate setting of wait_timeout variable which will kill stuck/sleep threads after a certain time. Solution 1: Verify Implicit Transactions Due to Autocommit; Solution 2: Increase the Timeout with innodb_lock_wait_timeout; Solution 3: Check and Adjust Transaction Isolation Levels; Solution 4: Identify and Kill the Blocking Processes Jan 7, 2023 · metadata lock的超时时间是lock_wait_timeout，并不是innodb_lock_wait_timeoutMySQL 5. PROCESSLIST select * from performance_schema. However I recently encounter permanantly the error "Waiting for table metadata lock". I'm pretty sure I'm "commit"-ing every call, but when I try an ALTER TABLE, I have the "Waiting for table metadata lock" in my processlist. Dec 18, 2022 · But LOCK TABLES acquires a different type of lock. One session is holding a lock on a table while another session tries to acquire the same lock on the same table. 说到lock_wait_timeout我们就不得不提到 metadata locks Mar 20, 2018 · Even simpler repro: create table test1( a int not null, b char(2) not null, primary key(a, b) ) ENGINE=INNODB; create table test2( a int not null, b char(2) not null, primary key(a, b) ) ENGINE=INNODB; LOCK TABLES `test`. 5 (on a staging server, of course). The default is 31536000. In order for MySQL to establish this lock it has to wait for any query against the table in question to finish, and in turn, any query on the table that occurs after the lock request has to wait for the Jul 28, 2022 · 【问题】Mysql Waiting for table metadata lock 解决方案 修改lock_wait_timeout时间. If a lock is held too long, any other transaction that needs to lock the same items will risk timing out. To set your transaction to wait longer, increase the innodb_lock_wait_timeout parameter value based on your MySQL workload. lock_type: The lock mode, either LOCKING_SERVICE_READ or LOCKING_SERVICE_WRITE to acquire read locks or write locks, respectively. 修改lock_wait_timeout时间 可以通过修改MySQL的参数lock_wait_timeout来解决Waiting for table metadata lock问题。该参数表示当一个线程在等待metadata lock时，最长等待的时间，单位为秒。 Apr 1, 2025 · metadata lock的超时时间是lock_wait_timeout，并不是innodb_lock_wait_timeoutMySQL 5. Apr 23, 2025 · Code Snippets: Here’s an example of how to set a metadata lock timeout in MySQL: SET GLOBAL lock_wait_timeout = 60; This command sets the global lock wait timeout to 60 seconds, which can help manage long-running transactions effectively. Jun 16, 2019 · mysql> begin; mysql> select * from test. The metadata lock's timeout is determined by the value of the lock_wait_timeout server system variable (in seconds). The offensive transaction is waiting for the row lock to be released by another transaction. OBJECT_TYPE. Dec 17, 2013 · 概述 随着5. 这种方法可以减小Metadata Lock的 粒度 ，降低锁定时间，但需要谨慎操作，以确保数据一致性。 方法三：调整等待时间. The lock is exclusive. 0，使用方法2及时提交或者缩短SQL执行时间（优化SQL），可以减少Waiting for table metadata lock出现次数。 Dec 27, 2013 · MySQL uses metadata locking to manage concurrent access to database objects and to ensure data consistency. THREADS B WHERE 1 = 1 AND A. When running an in-place online DDL operation, the thread that runs the ALTER TABLE statement applies an online log of DML operations that were run concurrently on the same table from other connection threads. Jul 21, 2011 · That is a bug in and of itself. I've been trying to deal with this ever since I upgraded to 5. 修改lock_wait_timeout时间 可以通过修改MySQL的参数lock_wait_timeout来解决Waiting for table metadata lock问题。该参数表示当一个线程在等待metadata lock时，最长等待的时间，单位为秒。 Aug 4, 2017 · MySQL의 잠금 특성을 확인하기 위한 실험 결과입니다. As I began to dig into the Percona Toolkit bug he reported concerning this change apropos pt-online-schema-change , I discovered something about lock_wait_timeout that GET_LOCK(str,timeout) Tries to obtain a lock with a name given by the string str, using a timeout of timeout seconds. FOR UPDATE is a data (i. 224 app_user Trx read view will not see trx with id >= 1742251019747, sees < 1742250438378 OBJECT_TYPE. Everyday, we would store close to 2 million rows in the table. threads *DB의 특정 계정에 대해 특정시간 이상 Metadata lock 발송 건을 counting SELECT COUNT(*) CNT FROM PERFORMANCE_SCHEMA. Jan 30, 2013 · Where would I set the maximum time a query will wait for a lock in MySQL 5. 12. From the documentation: This variable specifies the timeout in seconds for attempts to acquire metadata locks. 6，使用方法1处理MySQL 5. 3版本加入metadata lock以后，由于SESSION 1先查询了TABLE1，持有TABLE1的metadata lock，会导致SESSION 2等待，直到SESSION 1提交。 正因为如此，MySQL在5. innodb的dml操作的行级锁的等待时间，默认50秒. 200. 3), or 86400 (1 day, MariaDB >= 10. TABLE: Lock: Submitted: 18 Sep 2024 12:45: Modified: 27 Sep 2024 13:55 May 4, 2025 · MySQLのロックを適切に管理していますか？本記事では、ロックの基本概念から、バージョンごとのロック状態の確認方法、ロックの解除手順、デッドロック回避のベストプラクティスまで詳しく解説します。安全で効率的なデータベース運用のために、ぜひご覧ください。 GET_LOCK(str,timeout) Tries to obtain a lock with a name given by the string str, using a timeout of timeout seconds. 6 DB with MyISAM tables under FreeBSD 8. PROCESSLIST_ID, t. You don't need to reboot the affected instance. The value is one of GLOBAL, SCHEMA, TABLE, FUNCTION, PROCEDURE, TRIGGER (currently unused), EVENT, COMMIT, USER LEVEL LOCK, TABLESPACE, or LOCKING SERVICE. For more information, see innodb_lock_wait_timeout on the MySQL website. PROCESSLIST_TIME, LEFT(e. 4). 0. 3版本中引入了Metadata lock: DDL语句打破了事务的隔离级别在5. More void mysql_lock_abort_for_thread (THD *thd, TABLE *table) Abort one thread / table combination. (The INFORMATION_SCHEMA INNODB_TRX table indicates transaction state values. 3. There does not appear to be anything wrong with the imported data, but the warn Take a look to see if your database is fine tuned, especially the transaction isolation. This invariant is enforced by asserts in MDL_context::acquire_locks. `test1` RENAME `test`. To have the entire transaction roll back, start the server with --innodb-rollback-on-timeout enabled. Apr 23, 2025 · Use mysql unlock metadata lock: Configurable Timeout Setting. MySQL在进行alter table等DDL操作时，有时会出现Waiting for table metadata lock的等待场景。而且，一旦alter table TableA的操作停滞在Waiting for table metadata lock的状态，后续对TableA的任何操作（包括读）都无法进行，因为他们也会在Opening tables的阶段进入到Waiting for table metadata lock的锁等待队列。 This function cannot be called while holding LOCK_open_mutex. This is implemented as a table lock, outside the storage engine layer (notice the lack of "innodb" in the variable name). Nov 9, 2021 · Id User Host db Command Time State Info; 25800: root: localhost:51282: mydb: Sleep: 630: Waiting for table metadata lock: select id, name: 25803: root: localhost Jan 15, 2021 · lock_wait_timeout：数据结构ddl操作的锁的等待时间; 如何查看innodb_lock_wait_timeout的具体值？ SHOW VARIABLES LIKE 'innodb_lock_wait_timeout' 如何修改innode lock wait timeout的值？ 参数修改的范围有Session和Global，并且支持动态修改，可以有两种方法修改： 方法一： 通过下面语句 Sep 16, 2022 · 为了防止这种情况，表查询开始MySQL会在表上加一个锁，来防止被别的session修改了表定义，这个锁就叫‘metadata lock’，简称MDL，翻译成中文也叫‘元数据锁’。 二、MDL和行锁有什么区别？ metadata lock是表级锁，是在server层加的，适用于所有存储引擎。 Jun 3, 2024 · Hello, the query on performance_schema. Mar 29, 2017 · MySQL Waiting for table metadata lock问题可以从以下两个方面解决： 1. thread_id Nov 20, 2010 · Renamed open_and_lock_tables_derived() to open_and_lock_tables(). Solution 1: Verify Implicit Transactions Due to Autocommit; Solution 2: Increase the Timeout with innodb_lock_wait_timeout; Solution 3: Check and Adjust Transaction Isolation Levels; Solution 4: Identify and Kill the Blocking Processes Apr 24, 2021 · Background. Metadata locking applies not just to tables, but also to schemas, stored programs (procedures, functions, triggers, scheduled events), tablespaces, user locks acquired with the GET_LOCK() function (see Locking Functions), and locks acquired with the locking service Apr 8, 2020 · But in the given test for partition table even with one metadata lock, lock_wait_timeout taking twice the time as compared to its current timeout value. The default value of lock_wait_timeout is 31536000 seconds -- i. In the case of a long running or inactive transaction, an online DDL operation can time out waiting for an exclusive metadata lock. row) lock, not a metadata lock. Back in those days when I was working with an org, we had a Mysql table which would store voluminous data. example: lock This function cannot be called while holding LOCK_open_mutex. 4 节，“元数据锁定”。 元数据锁定不仅适用于表，还适用于模式、存储程序（过程、函数、触发器、计划事件）、表空间、使用 get_lock()函数获取的用户锁（请参阅 第 12. g. 20 [에러] ERROR 1932 (42S02): Table [테이블명] doesn't exist in engine 2017. 13. According to the MySQL Documentation on MetaData Locking : To ensure transaction serializability, the server must not permit one session to perform a data definition language (DDL) statement on a table that is used This function cannot be called while holding LOCK_open_mutex. MySQL. Aug 10, 2016 · [mysqld] innodb_lock_wait_timeout=120 and restart mysql. Jun 13, 2024 · MySQL Waiting for table metadata lock问题可以从以下两个方面解决： 1. For more details on different InnoDB locks and the types of locks that can cause conflicts, see InnoDB Locking in the MySQL documentation. ) The Performance Schema data_locks table holds one or more rows for each LOCK WAIT transaction, indicating any lock requests that prevent its progress. 但为什么出现这种现象？"table metadata lock"又是什么锁？ 从"table metadata lock"的名称，可以知道他是个表锁，"metadata lock"简称为 MDL ，即 元数据锁 ，从 MySQL 5. 1 year. ロックの種類. 07 16:54:42. The timeout for link metadata requests can be configured in the config. It can also occur when we perform maintenance operations on tables, DELETE tables, or try to access the WRITE lock on table-level (using this query LOCK TABLE table_name WRITE; ). Oct 21, 2021 · テーブルロックは LOCK TABLES tbl_name lock_typeを実行すると取得することができます。 tbl_nameには対象のテーブル名を、lock_typeにはロックの種類を指定します。 在使用mysql的时候，我们有时会碰到Waiting for table metadata lock的锁等待。但是这个锁等待比较特殊，在innodb_lock_wait和show engine innodb status 表里面都查不到。 Feb 28, 2013 · Like Ovais said in Implications of Metadata Locking Changes in MySQL 5. InnoDB lock wait timeout can cause two major implications: GET_LOCK() で取得された一意の名前付きロックは、パフォーマンススキーマの metadata_locks テーブルに表示されます。 OBJECT_TYPE カラムには USER LEVEL LOCK と示され、 OBJECT_NAME カラムにはロック名が示されます。 Dec 29, 2013 · OBJECT_TYPE. Metadata locking applies not just to tables, but also to schemas, stored programs (procedures, functions, triggers, scheduled events), tablespaces, user locks acquired with the GET_LOCK() function (see Section 12. The amount of time the transaction will wait depends on the value in the property innodb_lock_wait_timeout defined at the global or session level. 最近生产的MySQL数据库出现锁表的情况，通过show processlist;发现下图状态（模拟）waiting for table metadata lock Sep 17, 2024 · I recently upgraded the image to the latest major version and noticed some strange warnings when trying to import an existing SQL dump during initialisation. @ sql/sql_base. 5. json file. OBJECT_SCHEMA = '(DB명)' AND B GET_LOCK(str,timeout) Tries to obtain a lock with a name given by the string str, using a timeout of timeout seconds. 1k次，点赞10次，收藏17次。MySQL 5. 29 Dec 27, 2013 · MySQL uses metadata locking to manage concurrent access to database objects and to ensure data consistency. THREAD_ID AND A. I use the mysql. The innodb_lock_wait_timeout parameter is dynamic. schema_table_lock_waits，但此视图查询结果有bug，不是很准确，建议大家还是参考上面sql。 Oct 19, 2015 · session中在session级别设置 lock_wait_timeout 参数，防止 metadata lock 被一直锁住。 8）mysql命令行工具中执行的 DDL 语句不会受到 autocommit=on/off 的影响，DDL 语句自动开始事务，结束时自动提交事物 ； 9） DDL语句的最大危害之处 ： A long running or inactive transaction that holds a metadata lock on the table can cause an online DDL operation to timeout. Since opening and locking the MERGE table and its children failed, the tables would be closed and the metadata locks released. `test1_tmp_16810`; # This will transfer the Table MDL set by LOCK A lock wait timeout causes InnoDB to roll back the current statement (the statement that was waiting for the lock and encountered the timeout). 15 14:40 浏览量：89. The value is one of GLOBAL, SCHEMA, TABLE, FUNCTION, PROCEDURE, TRIGGER (currently unused), EVENT, COMMIT, USER LEVEL LOCK, TABLESPACE, BACKUP LOCK, or LOCKING SERVICE. Dec 29, 2013 · MySQL uses metadata locking to manage concurrent access to database objects and to ensure data consistency. `test1` WRITE; ALTER TABLE `test`. mytable; +-----+ | answer | +-----+ | 42 | +-----+ In the second window, try to truncate that table. com; Downloads; Documentation; Developer Zone Feb 2, 2023 · 实际上，MySQL也提供了一个类似的视图来解决metadata lock问题，视图名称为sys. MySQLには大きく分けて2つのロックがあります - InnoDBロック 1 - メタデータロック 2. schema_table_lock_waits，但此视图查询结果有bug，不是很准确，建议大家还是参考上面sql。 Nov 11, 2024 · Why Do You See the “Lock Wait Timeout Exceeded” Error? Common Solutions to Fix the Lock Wait Timeout Issue. 9. The Effects of an InnoDB Lock Wait Timeout. It happen nearly all the time and I do Feb 2, 2024 · The Waiting for table metadata lock may occur when we DELETE or CREATE an index and modify the table’s structure. To avoid deadlocks, we do not try to obtain exclusive metadata locks in LOCK TABLES mode, since in this mode there may be other metadata locks already taken by the current connection, and we must not wait for MDL locks while holding locks. 09. 15, “Locking Functions”), and locks acquired with the locking service Oct 19, 2015 · 而且， 一旦alter table TableA的操作停滞在Waiting for table metadata lock的状态，后续对TableA的任何操作（包括读）都无法进行， 因为他们也会在Opening tables的阶段进入到Waiting for table metadata lock的锁等待队列 。如果是产品环境的核心表出现了这样的锁等待队列，就会造成 Apr 29, 2013 · If an InnoDB table is being accessed at all via SELECT or DML (INSERT, UPDATE, DELETE), you should rightly expect a metadata lock. MySQL uses metadata locking to manage concurrent access to database objects and to ensure data consistency; see Metadata Locking. OWNER_THREAD_ID=t. Mar 11, 2020 · The offensive transaction is not fast enough to commit or roll back the transaction within innodb_lock_wait_timeout duration. If you are not sure whether your file system requires an fsync() system call to synchronize file system metadata changes, use O_DIRECT instead. This timeout applies to all statements that use metadata locks. Jan 7, 2023 · metadata lock的超时时间是lock_wait_timeout，并不是innodb_lock_wait_timeoutMySQL 5. waiting for table metadata lock. MySQL uses metadata locking to manage concurrent access to database objects and to ensure data consistency. 解决MySQL中'Waiting for table metadata lock'问题 作者：php是最好的 2024. Mar 2, 2016 · My MySQL database serves three webapps as the storage backend. Dec 29, 2013 · The Performance Schema metadata_locks table exposes metadata lock information, which can be useful for seeing which sessions hold locks, are blocked waiting for locks, and so forth. 6, but there was an important metadata locking change in MySQL 5. GET_LOCK(str,timeout) Tries to obtain a lock with a name given by the string str, using a timeout of timeout seconds. metadata lock also has similar parameter control: Nov 23, 2022 · Any time you make a change to a table a metadata lock is needed to ensure consistency between the table itself and MySQL’s data dictionary. Check your database transaction isolation level in MySQL: Jun 17, 2022 · Long-running statements likely indicate resource contention. Update 1 : Here's a simple example that demonstrates why innodb_lock_wait_timeout is not sufficient to ensure that the second transaction is not Jan 6, 2023 · Waiting for table metadata lock 1205 - Lock wait timeout exceeded; try restarting transaction MySQL如果频繁的修改一个表的数据，那么这么表会被锁死。 造成假死现象。 The --innodb-status-file startup option controls whether InnoDB creates a file named innodb_status. Aug 21, 2020 · ©著作权归作者所有,转载或内容合作请联系作者 平台声明：文章内容（如有图片或视频亦包括在内）由作者上传并发布，文章内容仅代表作者本人观点，简书系信息发布平台，仅提供信息存储服务。 Feb 13, 2012 · this is my own logic to generate custom auto primary key, I have not used any transaction or lock statement for concurrency then also I am seeing intended row was some how get locked (I think it is own innodb row locks not my transaction lock) and my update query start generating errors like this becuase i have default 50 value for innodb_lock Dec 12, 2024 · アソビュー！ Advent Calendar 2024 12日B面 はじめに こんにちは。アソビューでエンジニアをやっています。小池です。 最近、MySQLのテーブルにインデックス追加 (ALTER TABLE) をしたのですが、その際にメタデータロックを発生させてしまい、一時的な障害につながりました。 When innodb_deadlock_detect is disabled, InnoDB relies on innodb_lock_wait_timeout for transaction rollback when a deadlock occurs. More MYSQL_LOCK * mysql_lock_merge (MYSQL_LOCK *a, MYSQL_LOCK *b) bool lock_schema_name (THD *thd, const char *db) Obtain an Nov 20, 2010 · This could for example happen if a child table did not exist or if a lock timeout happened while waiting for a conflicting metadata lock to disappear. The main part of code is in PHP, but the problem arises, when I launch the self-written on C++ chat-server. 7，先判断是否开启了metadata_locks表特性，如果开启了使用方法2，否则使用方法1MySQL 8. 6. 3版本后引入了Metadata lock锁，事务释放后才会释放Metadata lock，因此，在事务完成之前，DDL是无法执行的。 May 5, 2024 · ---TRANSACTION 1742251019746, ACTIVE 283392 sec 230145 lock struct(s), heap size 29685288, 1531889 row lock(s), undo log entries 1527774 MySQL thread id 1891102408, OS thread handle 0x7f7d8c132700, query id 59116541146 10. innodb_lock_wait_timeout can be set at runtime with the SET GLOBAL or SET SESSION statement. 2 interactive_timeout & wait_timeout. 5 开始引入的，他是基于表元数据(表结构)的锁， MDL锁 是为了保证并发环境下元数据和表数据的结构一致性 Mar 20, 2018 · Even simpler repro: create table test1( a int not null, b char(2) not null, primary key(a, b) ) ENGINE=INNODB; create table test2( a int not null, b char(2) not null, primary key(a, b) ) ENGINE=INNODB; LOCK TABLES `test`. e. Prior to MySQL 8. h for DB For information on tuning Aurora MySQL performance using wait events, see Tuning Aurora MySQL with wait events. 14, “Locking Functions”), and locks acquired with the locking service Feb 1, 2021 · innodb_lock_wait_timeout The length of time in seconds an InnoDB transaction waits for a row lock before giving up. 3引入MDL，更多的Query被“Waiting for table metadata lock”给'炕'了SHOW PROCESSLIST的输出也有之前的"Locked"变得粒度更加细的&#39;Waiting for table metada lock_num: The number of names in the lock_names array. Additionally, a pending exclusive metadata lock requested by an online DDL operation blocks subsequent transactions on the table. 15 节，“锁定函数”），以及使用第 5. Aurora MySQL uses metadata locking to manage concurrent access to database objects and to ensure data consistency. 简介：在MySQL中，'Waiting for table metadata lock'是一个常见的错误，通常发生在多个线程尝试同时修改表结构时。本文将介绍此问题的原因和几种常见的解决方法。 Jul 8, 2011 · ** once this happens, even if i kill that thread manually, or it times out (when i set a low lock_timeout) it will always freeze each subsequent time that alter table is issued on that table. However, note that its default value is 31536000 (1 year, MariaDB <= 10. It will wait for a number of seconds equal to the lock_wait_timeout configuration option. SQL_TEXT,40) from metadata_locks mdl LEFT JOIN threads t on mdl. sdqlu ddalr xzmuqjt nyus oozumtr fdnwr ppyn jwnow arlqgs okcu