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本篇內容主要講解“mysql InnoDB鎖等待的查看以及分析”，感興趣的朋友不妨來看看。本文介紹的方法操作簡單快捷，實用性強。下面就讓小編來帶大家學習“mysql InnoDB鎖等待的查看以及分析”吧!
在InnoDB Plugin之前，一般通過show full processlist和show engine innodb status命令查看當前的數據庫請求，然后再判斷當前事務中鎖的情況。隨著mysql的發展，已經提供更加便捷的方法來監控數據庫中的鎖等待現象了。
在information_schema下面有三張表:INNODB_TRX、INNODB_LOCKS、INNODB_LOCK_WAITS，通過這三張表，可以更簡單地監控當前的事務并分析可能存在的問題。
INNODB_TRX表及結構
| Column name | Description |
| TRX_ID | Unique transaction ID number, internal to InnoDB. (Starting in MySQL 5.6, these IDs are not created for transactions that are read-only and non-locking. See Optimizing InnoDB Read-Only Transactions for details.) |
| TRX_WEIGHT | The weight of a transaction, reflecting (but not necessarily the exact count of) the number of rows altered and the number of rows locked by the transaction. To resolve a deadlock, InnoDB selects the transaction with the smallest weight as the “victim” to rollback. Transactions that have changed non-transactional tables are considered heavier than others, regardless of the number of altered and locked rows. |
| TRX_STATE | Transaction execution state. One of RUNNING, LOCK WAIT, ROLLING BACK or COMMITTING. |
| TRX_STARTED | Transaction start time. |
| TRX_REQUESTED_LOCK_ID | ID of the lock the transaction is currently waiting for (if TRX_STATE is LOCK WAIT, otherwise NULL). Details about the lock can be found by joining with INNODB_LOCKS on LOCK_ID. |
| TRX_WAIT_STARTED | Time when the transaction started waiting on the lock (if TRX_STATE is LOCK WAIT, otherwise NULL). |
| TRX_MYSQL_THREAD_ID | MySQL thread ID. Can be used for joining with PROCESSLIST on ID. See Section 14.17.2.3.1, “Potential Inconsistency with PROCESSLIST Data”. |
| TRX_QUERY | The SQL query that is being executed by the transaction. |
| TRX_OPERATION_STATE | The transaction's current operation, or NULL. |
| TRX_TABLES_IN_USE | The number of InnoDB tables used while processing the current SQL statement of this transaction. |
| TRX_TABLES_LOCKED | Number of InnoDB tables that the current SQL statement has row locks on. (Because these are row locks, not table locks, the tables can usually still be read from and written to by multiple transactions, despite some rows being locked.) |
| TRX_LOCK_STRUCTS | The number of locks reserved by the transaction. |
| TRX_LOCK_MEMORY_BYTES | Total size taken up by the lock structures of this transaction in memory. |
| TRX_ROWS_LOCKED | Approximate number or rows locked by this transaction. The value might include delete-marked rows that are physically present but not visible to the transaction. |
| TRX_ROWS_MODIFIED | The number of modified and inserted rows in this transaction. |
| TRX_CONCURRENCY_TICKETS | A value indicating how much work the current transaction can do before being swapped out, as specified by the innodb_concurrency_tickets option. |
| TRX_ISOLATION_LEVEL | The isolation level of the current transaction. |
| TRX_UNIQUE_CHECKS | Whether unique checks are turned on or off for the current transaction. (They might be turned off during a bulk data load, for example.) |
| TRX_FOREIGN_KEY_CHECKS | Whether foreign key checks are turned on or off for the current transaction. (They might be turned off during a bulk data load, for example.) |
| TRX_LAST_FOREIGN_KEY_ERROR | Detailed error message for last FK error, or NULL. |
| TRX_ADAPTIVE_HASH_LATCHED | Whether or not the adaptive hash index is locked by the current transaction. (Only a single transaction at a time can modify the adaptive hash index.) |
| TRX_ADAPTIVE_HASH_TIMEOUT | Whether to relinquish the search latch immediately for the adaptive hash index, or reserve it across calls from MySQL. When there is no AHI contention, this value remains zero and statements reserve the latch until they finish. During times of contention, it counts down to zero, and statements release the latch immediately after each row lookup. |
| TRX_IS_READ_ONLY | A value of 1 indicates the transaction is read-only. (5.6.4 and up.) |
| TRX_AUTOCOMMIT_NON_LOCKING | A value of 1 indicates the transaction is a SELECT statement that does not use the FOR UPDATE or LOCK IN SHARED MODE clauses, and is executing with the autocommit setting turned on so that the transaction will only contain this one statement. (5.6.4 and up.) When this column and TRX_IS_READ_ONLY are both 1, InnoDB optimizes the transaction to reduce the overhead associated with transactions that change table data. |
比較常用的列：
trx_id:InnoDB存儲引擎內部唯一的事物ID
trx_status:當前事務的狀態
trx_status:事務的開始時間
trx_requested_lock_id：等待事務的鎖ID
trx_wait_started：事務等待的開始時間
trx_weight：事務的權重，反應一個事務修改和鎖定的行數，當發現死鎖需要回滾時，權重越小的值被回滾
trx_mysql_thread_id：MySQL中的進程ID，與show processlist中的ID值相對應
trx_query：事務運行的SQL語句
INNODB_LOCKS
| Column name | Description |
| LOCK_ID | Unique lock ID number, internal to InnoDB. Treat it as an opaque string. Although LOCK_ID currently contains TRX_ID, the format of the data in LOCK_ID is not guaranteed to remain the same in future releases. Do not write programs that parse the LOCK_ID value. |
| LOCK_TRX_ID | ID of the transaction holding this lock. Details about the transaction can be found by joining with INNODB_TRX on TRX_ID. |
| LOCK_MODE | Mode of the lock. One of S, X, IS, IX, S_GAP, X_GAP, IS_GAP, IX_GAP, or AUTO_INC for shared, exclusive, intention shared, intention exclusive row locks, shared and exclusive gap locks, intention shared and intention exclusive gap locks, and auto-increment table level lock, respectively. Refer to the sections Section 14.5.3, “InnoDB Lock Modes” and Section 14.5.2, “The InnoDB Transaction Model and Locking” for information on InnoDB locking. |
| LOCK_TYPE | Type of the lock. One of RECORD or TABLE for record (row) level or table level locks, respectively. |
| LOCK_TABLE | Name of the table that has been locked or contains locked records. |
| LOCK_INDEX | Name of the index if LOCK_TYPE='RECORD', otherwise NULL. |
| LOCK_SPACE | Tablespace ID of the locked record if LOCK_TYPE='RECORD', otherwise NULL. |
| LOCK_PAGE | Page number of the locked record if LOCK_TYPE='RECORD', otherwise NULL. |
| LOCK_REC | Heap number of the locked record within the page if LOCK_TYPE='RECORD', otherwise NULL. |
| LOCK_DATA | Primary key value(s) of the locked record if LOCK_TYPE='RECORD', otherwise NULL. This column contains the value(s) of the primary key column(s) in the locked row, formatted as a valid SQL string (ready to be copied to SQL commands). If there is no primary key then the InnoDB internal unique row ID number is used. If a gap lock is taken for key values or ranges above the largest value in the index, LOCK_DATA reports “supremum pseudo-record”. When the page containing the locked record is not in the buffer pool (in the case that it was paged out to disk while the lock was held), InnoDB does not fetch the page from disk, to avoid unnecessary disk operations. Instead, LOCK_DATA is set to NULL. |
INNODB_LOCK_WAITS
| Column name | Description |
| REQUESTING_TRX_ID | ID of the requesting transaction. |
| REQUESTED_LOCK_ID | ID of the lock for which a transaction is waiting. Details about the lock can be found by joining with INNODB_LOCKS on LOCK_ID. |
| BLOCKING_TRX_ID | ID of the blocking transaction. |
| BLOCKING_LOCK_ID | ID of a lock held by a transaction blocking another transaction from proceeding. Details about the lock can be found by joining with INNODB_LOCKS on LOCK_ID. |
以上這些表，其實只要知道其中比較常用的字段，就差不多能夠滿足日常的工作需求了，下面通過測試進行演示；
一、準備工作
1、在test下面隨便創建一張表john，并取消自動commit操作，腳本如下：
| mysql> use information_schema Database changed mysql> select count(*) from tables; mysql> create table test.john as select * from tables;
mysql> insert into john select * from john; （經過幾次插入后john表的數據671744行）
mysql> set @@autocommit=0; （取消數據庫的自動commit） |
二、進行表john加鎖操作，腳本如下：
mysql> select count(*) from john for update; |
在另外一個窗口中監控innodb鎖的狀態；
mysql> SELECT * FROM INNODB_TRX\G; |
trx_id: B14 只是持有鎖，但并沒有產生鎖等待；
三、模擬鎖等待
3.1 在另外一個窗口中，執行語句：
| mysql> select count(*) from john where table_name='CHARACTER_SETS' for update; |
3.2 查看當前鎖等待的情況
INNODB_TRX的鎖情況：
mysql> SELECT * FROM INNODB_TRX\G; |
請注意：因為我們只有模擬兩個session，所以這邊只有兩個會話。（因此一個處于鎖等待，另外一個必然就是持有鎖的對象。實際的生產環境中可能這邊會出現很多列，所以需要用下面的語句才能判斷：鎖等待和持有鎖對象的匹配關系）
3.3 鎖等待和持有鎖的相互關系
mysql> SELECT * FROM INNODB_LOCK_WAITS\G; ERROR: |
通過視圖INNODB_LOCK_WAITS可以清晰的看到B14持有鎖，而B15處于鎖等待；
3.4 鎖等待的原因
mysql> SELECT * FROM INNODB_LOCKS\G; |
可以看到持有鎖的模式、對象
3.5 在進程里面查看狀態
|
Id值為8的進程，Info顯示為NULL值，可以推斷當前的session由于未進行commit導致鎖未釋放的；
總結：通過以上幾個視圖，就可以很快速的判斷出鎖等待的對象及原因了，從這上面也可以看出mysql管理更加便捷和容易了；
到此，相信大家對“mysql InnoDB鎖等待的查看以及分析”有了更深的了解，不妨來實際操作一番吧！這里是億速云網站，更多相關內容可以進入相關頻道進行查詢，關注我們，繼續學習！
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