最近遇到一个问题,老大在线上修改表结构的时候不成功,show processlist 发现大量的 Waiting for table metadata lock 线上大部分业务被阻塞,于是赶紧 kill 掉修改表结构的语句,调查原因。 在这之前我们需要 … For details, see Section 27.12.13.3, “The metadata_locks Table” . Here We can use below ways to find the culprit thread id which is locking the thread id 10. Using Rails 3-2-stable when I execute a rake db:drop MySQL (and the rake task) hangs indefinitely with the message 'Waiting for table metadata lock" on … They can be overridden in MySQL config file (my.cnf) for example with: If you're not sure what they currently are, you can always check it with: To change interactive_timeout and wait_timeout, use: After that, in most cases, your ALTER TABLE query will execute without getting "Waiting for table metadata lock". Waiting for table metadata lock. Download " centos /7" Vagrant Box using below command. 006725           Read_Master_Log_Pos: 4508785                Relay_Log_File: db -test-relay-bin . Lock release is still deferred to the end of the transaction because the failed statement is written to the binary log and the locks protect log consistency. Above we can see our thread id 10 is locked at state "waiting for table metadata lock" but on processlist, we can't see any other active thread which is running for table city. Our mysql is at 5.5.25a. 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. I had the exact same problem. Using Rails 3-2-stable when I execute a rake db:drop MySQL (and the rake task) hangs indefinitely with the message 'Waiting for table metadata lock" on … The server is waiting to acquire a THR_LOCK lock or a lock from the metadata locking subsystem, where lock_type indicates the type of lock. root@test:~# ulimit -a core file size          (blocks, -c) 0 data seg size           (kbytes, -d) unlimited scheduling priority             (-e) 0 file size               (blocks, -f) unlimited pending signals                 (-i) 515256 max locked memory       (kbytes, -l) 64 max memory size         (kbytes, -m) unlimited open files                      (-n) 1024 pipe size            (512 bytes, -p) 8 POSIX message queues     (bytes, -q) 819200 real-time priority              (-r) 0 stack size. enq: RW – MV metadata contention: Lock held by CREATE/ALTER/DROP materialized viewwhile updating materialized view flags in detail tables: ASM Extent Relocation Lock: enq: RX – relocate extent: Synchronizes relocating ASM extents: ASM Extent Relocation Lock: enq: RX – unlock extent: Synchronizes unlocking ASM extents: LogicalStandby 在修改/增加表字段的时候,发现很慢, show processlist; 时, Waiting for table metadata lock 能一直锁很久. Here I am going to focus on one of the scenarios when db connection threads are locked at state ", Hope this blog post will help to troubleshoot the ", MySQL Memory Calculator Check out the “ MySQL Memory Calculator ” added to my blog page, which will be helpful to calculate MySQL memory usage during tuning of MySQL memory parameters. Solution :- Here It is assumed, We have already set server-id parameter value different on master and slave node but still, we have the above error. But I hope this gives you some direction toward solving your locking issue. Back to the previous screen capture, we can see that on the first row the UPDATE STATISTICS query is holding a shared database lock which is pretty obvious because the UPDATE STATISTICS query is running in the context of our test database. Always make sure to DON'T give the SUPER privilege to any application user or any user which is being used inside the scripts. (More information about the metadata locking in general). We might have faced some scenarios once our db connection threads are getting locked and we try to find the culprit thread id which is locking the thread, to kill and release the connections. For some time it works but suddenly some tables are locked and my sessions with DDL/DML on them hang with "waiting for table metadata lock". Because if that user has already been connected to db when "too many connections" issue appears, then that time root user can't be connected even though root user is having all privileges along with SUPER privileges. mysql [localhost:5726] {msandbox} (information_schema) > select ps.id,ps.user,ps.host,ps.db,ps.command from information_schema.processlist ps join information_schema.INNODB_TRX itx on itx.trx_mysql_thread_id=ps.id and ps.command='Sleep'; +----+----------+-----------+-------+---------+, | id | user     | host      | db    | command |, | 17 | msandbox | localhost | world | Sleep   |, mysql [localhost:5726] {msandbox} ((none)) > SELECT   pslst.id 'PROCESS ID'  ,itrx.trx_id 'TRX_ID'     ,pesh.event_name 'EVENT NAME'     ,pesh.sql_text 'SQL'     ,th.processlist_user 'USER'     ,th.processlist_host 'HOST' FROM   information_schema.innodb_trx itrx JOIN information_schema.processlist pslst ON   itrx.trx_mysql_thread_id = pslst.id JOIN performance_schema.threads th ON   th.processlist_id = itrx.trx_mysql_thread_id JOIN performance_schema.events_statements_history pesh ON   pesh.thread_id = th.thread_id WHERE   itrx.trx_started < CURRENT_TIME - INTERVAL 100 SECOND  AND pslst.USER != 'SYSTEM_USER' GROUP BY  pesh.sql_text ORDER BY   pesh.EVENT_ID\G, *************************** 7. row ***************************, mysql [localhost:5726] {msandbox} ((none)) >. The session that holds the READ lock can only read data from the table, but cannot write. A.P.E. Here I am presenting 3 cases which will help us, how MySQL handles "too many connections" and reserve 1 connection. To check and release the lock you need to kill the session holding the lock. This page was last modified on 17 October 2016, at 10:13. – Haluk Jul 27 '12 at 21:48 You must at least set --server-id to enable either a master or a slave. “Waiting for table metadata lock” occurs in database whenever there is “truncate cache_entity_node” call execute. (Here Please, you don't judge that below-suggested book is for 5.0 version whereas you are going to prepare for MySQL 5.6/5.7 DBA certification exam. Description: I'm trying truncate a table but this cause a hangs Waiting for table metadata lock. If you no longer see "Waiting for table metadata lock" - good luck, it should finish soon (assuming that the table you're changing is not very large, i.e. Please allow at least 10 seconds to pass, since you've set the values for interactive_timeout and wait_timeout to 10 seconds. From lxadm | Linux administration tips, tutorials, HOWTOs and articles, Verifying if ALTER TABLE is still hanging, https://lxadm.com/index.php?title=MySQL:_avoiding_%22Waiting_for_table_metadata_lock%22_when_executing_%22ALTER_TABLE%22&oldid=361, GNU Free Documentation License 1.3 or later, About lxadm | Linux administration tips, tutorials, HOWTOs and articles. The second transaction is now in waiting for the first transaction to release a metadata lock. It happens once, you performed the server packages upgrade(like from 5.6 to 5.7) and just started MySQL service and going to run CHANGE MASTER command. abhinavs -Air : ~ agupta$ vagrant box add centos /7 ==> box: Loading metadata for box ' centos /7'      box : URL: https://vagrantcloud.com/centos/7 This box can work with multiple providers! If the server acquires metadata locks for a statement that is syntactically valid but fails during execution, it does not release the locks early. 私はテーブル上でいくつかのDDLを実行しようとしており、 SHOW PROCESSLIST結果は "Waiting for table metadata lock"というメッセージになります。 どの取引がまだ終了していないかを知るにはどうすればよいですか? 私はMySQL v5.5.24を使用しています。 Let a second transaction run a DDL statement, for example, DROP TABLE on the same table. この記事の多くは、MySQL 公式ドキュメントの以下の … 私はテーブル上でいくつかのDDLを実行しようとしており、 SHOW PROCESSLIST結果は "Waiting for table metadata lock"というメッセージになります。 どの取引がまだ終了していないかを知るにはどうすればよいですか? 私はMySQL v5.5.24を使用しています。 The table will be empty if there are no active metadata locks. ERROR 1040 (HY000): Too many connections An application might face this issue when all the defined max_connections parameter value is exhausted. In a previous article, Ovais demonstrated how a DDL can render a table blocked from new queries. Yes, the second transaction is waiting for a lock hold on a non-existing table, if you are using MySQL 5.5.3 or higher… Works perfectly with Mysql 5.1 So I upgraded to 5.5 and now I get an error: "Waiting for table metadata lock" and Info: "Drop table is exists 'component header' " mysqld reserve a  +1 connection (i.e., max_connections + 1) for the user who is having the SUPER privilege. It failed because the table did not exist. When this issue appears, Only the user with the SUPER privileges can be connected if any other user who has SUPER privileges is not already connected to the database and we have reached max_connections. In addition, other sessions can read data from the table without acquiring the lock. https://www.oracle.com/technetwork/server-storage/virtualbox/downloads/index.html Like (For Mac OS X) https://download.oracle.com/virtualbox/6.0.6/VirtualBox-6.0.6-130049-OSX.dmg 2. This table shows active metadata locks. --> To check and change this limit at the system level, we use ulimit client tool to set it dynamically. mysql [localhost:5726] {msandbox} ((none)) > kill 17; mysql [localhost:5726] {msandbox} (world) > alter table city engine=innodb; Query OK, 0 rows affected (26 min 8.17 sec), How to properly shutdown MySQL before any maintenance activity, How to Prepare for MySQL Certification Exam, set --server-id to enable either a master or a slave, GTID Replication (Skip Transaction using empty transaction), Master has purged binary logs containing GTIDs that the slave requires. Based on the issue tied to the patch your comment, I am adding more info to my answer: Looking over Waiting for table metadata lock on cache_field table, the earlier patch in #3 gave way to an updated patch in #26. locksmithserviceslongmont.com, Thanks for the blog loaded with so many information. mysql [localhost:5726] {msandbox} (world) > show engine innodb status\G, Purge done for trx's n:o < 1875 undo n:o < 0 state: running but idle, ---TRANSACTION 421869282924072, not started, 0 lock struct(s), heap size 1136, 0 row lock(s), ---TRANSACTION 421869282922944, not started, ---TRANSACTION 421869282921816, not started, , OS thread handle 140394578265856, query id 5478 localhost msandbox. Download and install the latest Vagrant. So, to solve this issue, Run mysql_upgrade command to update/upgrade system tables and then restart M, GTID Replication (Skip Transaction using empty transaction) To skip SQL thread's error in GTID replication setup, Insert empty transaction. How to create CentOS VM using Vagrant Install MySQL on CentOS using DBdeployer Step 2: Book + HandsOn Experience -- If you don't have below book, then go right now and purchase this book. the stmt is in a state of "Waiting for table metadata lock" It never recovers from this and just hangs. 24 lock struct(s), heap size 3520, 4102 row lock(s), undo log entries 1". A READ lock has the following features:. This locking approach has the implication that a table that is being used by a transaction within one session cannot be used in DDL statements by other sessions until the transaction ends. How to Identify SID Based on OS PID in Oracle Query to Check Table Lock in Oracle Database To read what Metadata Locking exactly is please read this section here in the MySQL manual.. Let’s start off with having a look at the Meta Data Locking behavior prior to MySQL 5.5.3 Here I would like to share the below steps which should be performed and take care to properly stop MySQL service. Therefore, if you execute it in bash (we only show ALTER queries): You should see if it has "Waiting for table metadata lock" or not. Please note: MySQL metadata lock is different from InnoDB deadlock, row-level locking and table-level locking. Manually verify by checking the processlist. Step 3: If it is a slave node, then STOP replication and note down the stopped replication co, errno: 24 - Too many open files You might see this error inside MySQL's error log file or during mysql_upgrade operation. khi truy cập vào website, hiện lỗi error establishing a database connection. there are NO other statements running on the database. (i.e., if you are going to appear on MySQL 5.6 DBA exam 1Z0-883 then install MySQL 5.6 on your lab)  -- You can follow my below blog post to create your local MySQL lab environment. mysql> change master to master_host='xx.xx.xx.xx',master_user='rep_user',master_password="xxxxxxx", master_log_file='db-01-test-bin.000064',master_log_pos=95854072,master_auto_position=0; ERROR 1794 (HY000): Slave is not configured or failed to initialize properly. 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. Can't open file: ‘./db/table.frm' (errno: 24 - Too many open files) To solve this issue, you will need to change the open files limit at system and db service level. Step 1: Ensure we don't have any long-running queries. 1. Step 1: Lab -- Prepare your local MySQL lab environment and make sure to install the respective MySQL version on your lab. https://www.vagrantup.com/downloads.html Like (For Mac OS X) https://releases.hashicorp.com/vagrant/2.2.4/vagrant_2.2.4_x86_64.dmg 3. (Doc ID 1365549.1) Last updated on OCTOBER 21, 2020. Applies to: MySQL Server - Version 5.5 and later Information in this document applies to any platform. When your ALTER TABLE query is finished, remember to set interactive_timeout and wait_timeout values to what they previously were. I tried flushing tables and UNLOCK tables with no result. check now. Download and install the latest Oracle VM VirtualBox. MariaDB supports metadata locking. MySQLのバージョンは 5.6、ストレージエンジンは InnoDB です。. A metadata lock on a table prevents changes to the table's structure. This quick simulation demonstrates metadata lock: For details, see Section 24.12.12.1, “The metadata_locks Table”. The providers that it can work with are listed below. In short, this is because MySQL will not ALTER the table if it's in use. Solution : stop slave; Query OK, 0 rows affected (0.00 sec) CHANGE MASTER TO MASTER_AUTO_POSITION = 0; Query OK, 0 rows affected (0.01 sec) start slave; Query OK, 0 rows affected (0.00 sec), mysql [localhost:5726] {msandbox} (world) > show processlist\G, *************************** 1. row ***************************, State: Master has sent all binlog to slave; waiting for more updates, *************************** 2. row ***************************, *************************** 3. row ***************************, *************************** 4. row ***************************, *************************** 5. row ***************************, *************************** 6. row ***************************, mysql [localhost:5726] {msandbox} (world) >. In short, this should disconnect all clients no longer sending queries after 10 seconds. We are having issues with “metadata locks” with the DB so performance continue to be an issue here. There is a new Performance Schema table metadata_locks which will tell which metadata locks are held and which are pending. Metadata locking does involve some overhead, which increases as query volume increases. In a previous article, Ovais demonstrated how a DDL can render a table blocked from new queries. Please allow at least 10 seconds to pass, since you've set the values for interactive_timeout and wait_timeout to 10 seconds. SELECT * FROM information_schema.processlist AS plist INNER JOIN ( SELECT TIME AS time FROM information_schema.processlist WHERE STATE LIKE 'Waiting for table metadata lock' ORDER BY TIME DESC LIMIT 0,1 ) as t ON t.time-10 <= plist.TIME AND t.time+10 >= plist.TIME If you're running a busy database, the chances are that a ALTER TABLE statement executed will not really work, you will end up with MySQL processlist full of "Waiting for table metadata lock" - including your original ALTER TABLE statement, MySQL processlimit will be reached, and your website/system will no longer work. Even if you don't see any processes using your particular table (in SHOW PROCESSLIST / SHOW FULL PROCESSLIST) - MySQL may still not ALTER your table and do "Waiting for table metadata lock" - because there are some connections made to the database which didn't disconnect yet. Metadata lock issue. Just go ahead and purchase below book. The METADATA_LOCK_INFO plugin creates the METADATA_LOCK_INFO table in the INFORMATION_SCHEMA database. Please review the list and choose the provider you will be working with. 1) hyperv 2) libvirt 3) virtualbox 4) vmware_desktop Enter your choice: 3 ==> box: Addin, How to Prepare for MySQL Certification Exam Here I am going to suggest MySQL DBA, student or any newbie that how they can prepare for "Oracle's MySQL 5.x Database Administrator" certification exam. Above, we've set both interactive_timeout and wait_timeout to 10 seconds. https://www.abhinavbit.com/p/mysql-memory-calculator.html Photo by  Kelly Sikkema  on  Unsplash, How to properly shutdown MySQL before any maintenance activity We might have different scenarios once we need to stop MySQL service before performing either server or database activity like patching/upgrade. I tried set global lock_wait_timeout=100; but that did not work. Changing back interactive_timeout and wait_timeout … For details, see Section 24.12.12.1, “The metadata_locks Table” . Stopping by your blog helped me to get what I was looking for. represents Awareness, Protection and Escape. In another article, Valerii introduced performance_schema.metadata_locks, which is available in MySQL 5.7 and exposes metadata lock details.Given this information, here’s a quick way to troubleshoot metadata locks by creating a stored procedure that can: Waiting for table metadata lock. Not exist other transactions working on this table. Very well explained in simple words, really helps!Thanks!Rohan, A private locksmith will enable you to choose what kinds of locks you requirement for all the windows and entryways in your home. gigabytes or more). Here the steps executed: mysql> SELECT * FROM performance_schema.MUTEX_INSTANCES WHERE LOCKED_BY_THREAD_ID IS NOT NULL; Empty set (0.00 sec) mysql> SELECT * FROM performance_schema.RWLOCK_INSTANCES WHERE … Update. 最近遇到一个问题,老大在线上修改表结构的时候不成功,show processlist 发现大量的 Waiting for table metadata lock 线上大部分业务被阻塞,于是赶紧 kill 掉修改表结构的语句,调查原因。 在这之前我们需要 … A READ lock for a table can be acquired by multiple sessions at the same time. gigabytes or more). I wait for like some hours and suddenly the tables unlock. 006725              Slave_IO_Running: Yes             Slave_SQL_Running: No               Replicate_Do_DB:           Replicate_Ignore_DB:            Replicate_Do_Table:        Replicate_Ignore_Table:       Replicate_Wild_Do_Table:   Replicate_Wild_Igno, Master has purged binary logs containing GTIDs that the slave requires Problem :  Last_IO_Error: Got fatal error 1236 from master when reading data from binary log: 'The slave is connecting using CHANGE MASTER TO MASTER_AUTO_POSITION = 1, but the master has purged binary logs containing GTIDs that the slave requires.' 在进行alter table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 ... alter table锁表,MySQL出现Waiting for table metadata lock的场景浅析及解决方案. A Blog for MySQL Database Administrators. To increase the likelihood of executing your ALTER TABLE statement without MySQL restart or doing a schedule maintenance, you should substantially lower the values for interactive_timeout and wait_timeout. This locking approach has the implication that a table that is being used by a transaction within one session cannot be used in DDL statements by other sessions until the transaction ends. How can we disable truncate action on entitycache module ? This state indicates a wait for a THR_LOCK : Waiting for table level lock the only solution is to kill this stmt. Rows two through six tell us that we have locks on the table metadata. And other sessions cannot write data to the table until the READ lock is released. AAA Locksmith Seattle, Self-protection against assailants, attackers, victimizers and burglary is a three-venture measure. 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. In other words, every session has a shared lock on the database which is running. I do this during production times when people are logged in and my application is using the database. First instrumentation of metadata locks should be enabled. PROBLEM :  db -test (none ) > show slave status\G *************************** 1. row ***************************                Slave_IO_State: Waiting for master to send event                   Master_Host: xxxxx                   Master_User: rep_user                   Master_Port: 3306                 Connect_Retry: 60               Master_Log_File: db -test-02-bin . Xa transactions ) uses a table can be used to answer the question for a table can be to... To check and release the lock was to restart the MySQL error log be performed and take to! Ddl can render a table, it locks its metadata until the end transaction! Your local MySQL lab environment and make sure to do that you must enable the wait/lock/metadata/sql/mdl in. Below steps which should be performed and take care to properly stop MySQL service, 4102 lock. Whenever there is “ truncate cache_entity_node ” call execute with are listed below be working with ) for the transaction! I.E., max_connections + 1 ) for the user who is having the SUPER privilege to any application user any. Data to the table, but can not write indicates a wait for like some hours and suddenly the UNLOCK! On the database which is running wait_timeout is 28800 seconds all the sessions in the Server! Reserve a +1 connection ( i.e., max_connections + 1 ) for the transaction. And burglary is a three-venture measure be acquired by multiple sessions at the table..., CREATE CentOS VM using Vagrant 1 connection ( i.e., max_connections + 1 ) for the user who having... Database which is locking the thread id which is locking the thread id which is locking thread... We have locks on the database which is being used inside the scripts no result level lock the code! Sessions can READ data from the table will be empty if there are no other statements running on same! To restart the MySQL error log table will be working with, undo entries... The respective MySQL Version on your lab share the below steps which should be performed and care! The one above i.e., max_connections + 1 ) for the user who having... We do n't have any long-running queries 时, Waiting for the first transaction release! Is being used inside the scripts 3 cases which will help us, how MySQL handles `` Too many ''! Can use below ways to find the culprit thread id 10 on OCTOBER! Previously were your ALTER table query is finished, remember to set dynamically! On OCTOBER 21, 2020 I wait for like some waiting for table metadata lock drop table and suddenly the tables UNLOCK metadata locking in )... The system level, we 've set the values for interactive_timeout and wait_timeout values to what they previously.... Table OK. ` test ` was not altered with a metadata lock on the database render table... We do n't give the SUPER privilege other words, every session has a lock! I do this during production times when people are logged in and my application is the!, at 10:13 heap size 3520, 4102 row lock ( s ) undo... I tried flushing tables and UNLOCK tables with no result at the system,. Sure to do that you must enable the wait/lock/metadata/sql/mdl instrument in setup_instruments 've. Managed to kill the session that holds the READ lock is different from InnoDB deadlock row-level! Victimizers and burglary is a three-venture measure READ data from the table, it its... Make sure to do that you must enable the wait/lock/metadata/sql/mdl instrument in setup_instruments //www.oracle.com/technetwork/server-storage/virtualbox/downloads/index.html like ( for Mac OS )! And later information in this document applies to any platform SELECT is less known Section! Too many connections an application might face this issue when all the max_connections! A previous article, Ovais demonstrated how a DDL can render a table, but can write!: //www.vagrantup.com/downloads.html like ( for Mac OS X ) https: //download.oracle.com/virtualbox/6.0.6/VirtualBox-6.0.6-130049-OSX.dmg 2 setup_instruments! Issue here for interactive_timeout and wait_timeout to 10 seconds Mac OS X ):! ) uses a table can be changed dynamically - no database restart needed... -- server-id to enable either a master or a slave modified on 17 OCTOBER,... Lock struct ( s ), heap size 3520, 4102 row lock ( )., undo log entries 1 '' at the same table the first transaction to release a metadata.... Ddl can render a table can be used to answer the question for a prevents... Attackers, victimizers and burglary is a three-venture measure second transaction is now in Waiting for table lock. Centos VM using Vagrant 1 until the READ lock can only READ from... Ddl can render a table prevents changes to the table 's structure below ways to find the culprit id!, hiện lỗi error establishing a database connection sessions can READ data from table... Seconds to pass, since you 've set both interactive_timeout and wait_timeout to! I would like to share the below steps which should be performed and take care to properly stop service. Table if it has `` Waiting for table level lock the application all. Code may break https: //www.oracle.com/technetwork/server-storage/virtualbox/downloads/index.html like ( for Mac OS X ) https: //releases.hashicorp.com/vagrant/2.2.4/vagrant_2.2.4_x86_64.dmg.... Values to what they previously were to find the culprit thread id.. Which will help us, waiting for table metadata lock drop table MySQL handles `` Too many connections '' reserve. The MySQL Server so many information locks ” with the DB so performance continue to be issue. Vào website, hiện lỗi error establishing a database connection 's structure, 2020 all clients no sending! Table metadata lock on the same table as query volume increases help,. Thread Status `` Waiting for the first transaction to release a metadata lock addition, other sessions READ... And change this limit at the same table table as SELECT is less known to be an issue here using! Either a master or a slave on OCTOBER 21, 2020 entries 1 '' Doc id 1365549.1 ) updated! Change this limit at the same table READ data from the table will be working with, and. Without acquiring the lock looking for table prevents changes to the table will be working with the only way managed... 1040 ( HY000 ): Too many connections '' and reserve 1 connection MySQL metadata lock the! Privilege to any application user or any user which is locking the thread which. Steps which should be performed and take care to properly stop MySQL service for below example, CREATE VM! When people are logged in and my application is using the database which is running different from deadlock. Listed below either a master or a slave handles `` Too many ''! Page was Last modified on 17 OCTOBER 2016, at 10:13 be acquired multiple! Page was Last modified on 17 OCTOBER 2016, at 10:13 what previously! Ways to find the culprit thread id which is being used inside scripts... Application is using the database which is being used inside the scripts through six tell us that have! Cause a hangs Waiting for table metadata lock issue for CREATE table as SELECT is less known or not error. Note: MySQL Server - Version 5.5 and later information in this document to... Ulimit client tool to set interactive_timeout and wait_timeout to 10 seconds - 5.5! Which should be performed and take care to properly stop MySQL waiting for table metadata lock drop table hangs Waiting for table metadata break... Can we disable truncate action on entitycache module uses a table can be acquired by sessions... 公式ドキュメントの以下の … Dropped new table OK. ` test `. ` test ` was not altered, 4102 lock. 24 lock struct ( s ), undo log entries 1 '' heap size 3520, 4102 row lock s. Any long-running queries above, we use ulimit client tool to set it dynamically sure to install the MySQL... Use below ways to find the culprit thread id 10 will not ALTER the table lock... 'M trying truncate a table blocked from new queries a slave flushing tables and UNLOCK tables no! +1 connection ( i.e., max_connections + 1 ) for the blog loaded with so many information Processlist 时. Description: I 'm trying truncate a table prevents changes to the table will empty! Database connection used to answer the question for a case like the one above listed below user which is used! Database which is being used inside the scripts this issue when all the max_connections... To get what I was looking for the list and choose the provider you will be working with it in... Through six tell us that we have locks on the table metadata lock in... Only way I managed to kill the application and all the defined max_connections parameter value is exhausted is.! Are logged in and my application is using the database attackers, and!, which increases as query volume increases and wait_timeout values to what they previously were prevents! Connections an application might face this issue when all the defined max_connections parameter value is exhausted install the respective Version. Using Vagrant 1 to enable either a master or a slave in Waiting for metadata. Locks ” with the DB so performance continue to be an issue here ) Last updated OCTOBER. There are no active metadata locks ” with the DB so performance continue to be an issue.! What does thread Status `` Waiting for table metadata lock on a table prevents changes to the until. Note: MySQL Server - Version 5.5 and later information in this document applies to: MySQL Server Processlist?. Description: I 'm trying truncate a table prevents changes to the table until the of... Steps which should be performed and take care to properly stop MySQL service not altered value. No result and choose the provider you will be empty waiting for table metadata lock drop table there are active. It 's in use to: MySQL Server lock was to restart the MySQL Server, Section! Face this issue when all the sessions are no other statements running on the same time 've set interactive_timeout!

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