檢查線程信息 · mysql 8.0 中文文檔

## 8.14 檢查線程信息 When you are attempting to ascertain what your MySQL server is doing, it can be helpful to examine the process list, which is the set of threads currently executing within the server. 進程列表信息可以從以下來源中獲得: - `SHOW [FULL] PROCESSLIST` 語句: [Section 13.7.6.29, “SHOW PROCESSLIST 語法](https://dev.mysql.com/doc/refman/8.0/en/show-processlist.html) - [`SHOW PROFILE`](https://dev.mysql.com/doc/refman/8.0/en/show-profile.html) 語句: [Section 13.7.6.31, “SHOW PROFILES 語法](https://dev.mysql.com/doc/refman/8.0/en/show-profiles.html) - `INFORMATION_SCHEMA` [`PROCESSLIST`](https://dev.mysql.com/doc/refman/8.0/en/processlist-table.html) 表: [Section 25.19, “The INFORMATION_SCHEMA PROCESSLIST Table”](https://dev.mysql.com/doc/refman/8.0/en/processlist-table.html) - The [**mysqladmin processlist**](https://dev.mysql.com/doc/refman/8.0/en/mysqladmin.html) 命令: [Section 4.5.2, “**mysqladmin** — 管理 MySQL 服務器的客戶端”](https://dev.mysql.com/doc/refman/8.0/en/mysqladmin.html) - The Performance Schema [`threads`](https://dev.mysql.com/doc/refman/8.0/en/threads-table.html) table, stage tables, and lock tables: [Section 26.12.17, “Performance Schema Miscellaneous Tables”](https://dev.mysql.com/doc/refman/8.0/en/performance-schema-miscellaneous-tables.html), [Section 26.12.5, “Performance Schema Stage Event Tables”](https://dev.mysql.com/doc/refman/8.0/en/performance-schema-stage-tables.html), [Section 26.12.12, “Performance Schema Lock Tables”](https://dev.mysql.com/doc/refman/8.0/en/performance-schema-lock-tables.html). Access to [`threads`](https://dev.mysql.com/doc/refman/8.0/en/threads-table.html) does not require a mutex and has minimal impact on server performance. [`INFORMATION_SCHEMA.PROCESSLIST`](https://dev.mysql.com/doc/refman/8.0/en/processlist-table.html) and [`SHOW PROCESSLIST`](https://dev.mysql.com/doc/refman/8.0/en/show-processlist.html) have negative performance consequences because they require a mutex. [`threads`](https://dev.mysql.com/doc/refman/8.0/en/threads-table.html) also shows information about background threads, which [`INFORMATION_SCHEMA.PROCESSLIST`](https://dev.mysql.com/doc/refman/8.0/en/processlist-table.html) and [`SHOW PROCESSLIST`](https://dev.mysql.com/doc/refman/8.0/en/show-processlist.html) do not. This means that [`threads`](https://dev.mysql.com/doc/refman/8.0/en/threads-table.html) can be used to monitor activity the other thread information sources cannot. You can always view information about your own threads. To view information about threads being executed for other accounts, you must have the [`PROCESS`](https://dev.mysql.com/doc/refman/8.0/en/privileges-provided.html#priv_process) privilege. Each process list entry contains several pieces of information: - `Id` 是線程關聯的客戶端的連接標識符. - `User` 和 `Host` 表示與線程關聯的賬戶. - `db` 是線程默認的數據庫, 如果沒有選擇, 則為 NULL. - `Command` 和 `State` 表示線程正在做什么. 大多數狀態對應非常快速的操作, 如果一個線程在給定的狀態中停留了許多秒, 那么可能需要研究一下這個問題. - `Time` indicates how long the thread has been in its current state. The thread's notion of the current time may be altered in some cases: The thread can change the time with [`SET TIMESTAMP = value`](https://dev.mysql.com/doc/refman/8.0/en/set-variable.html). For a thread running on a slave that is processing events from the master, the thread time is set to the time found in the events and thus reflects current time on the master and not the slave. - `Info` contains the text of the statement being executed by the thread, or NULL if it is not executing one. By default, this value contains only the first 100 characters of the statement. To see the complete statements, use [`SHOW FULL PROCESSLIST`](https://dev.mysql.com/doc/refman/8.0/en/show-processlist.html). - The `sys` schema [processlist](https://dev.mysql.com/doc/refman/8.0/en/sys-processlist.html) view, which presents information from the Performance Schema [`threads`](https://dev.mysql.com/doc/refman/8.0/en/threads-table.html) table in a more accessible format: [Section 27.4.3.22, “The processlist and x$processlist Views”](https://dev.mysql.com/doc/refman/8.0/en/sys-processlist.html) - The `sys` schema [`session`](https://dev.mysql.com/doc/refman/8.0/en/sys-session.html) view, which presents information about user sessions (like the `sys` schema [`processlist`](https://dev.mysql.com/doc/refman/8.0/en/sys-processlist.html) view, but with background processes filtered out): [Section 27.4.3.33, “The session and x$session Views”(https://dev.mysql.com/doc/refman/8.0/en/sys-session.html)] The following sections list the possible `Command` values, and `State` values grouped by category. The meaning for some of these values is self-evident. For others, additional description is provided.