性能模式会记录阶段，这是语句执行过程中的步骤，例如解析语句、打开表或执行 filesort 操作。阶段对应于 SHOW PROCESSLIST 显示的线程状态，或在 Information Schema PROCESSLIST 表中可见的线程状态。当状态值发生变化时，阶段开始和结束。The Performance Schema instruments stages, which are steps during the statement-execution process, such as parsing a statement, opening a table, or performing a filesort operation. Stages correspond to the thread states displayed by SHOW PROCESSLIST or that are visible in the Information Schema PROCESSLIST table. Stages begin and end when state values change.

在事件层次结构中，等待事件嵌套在阶段事件中，阶段事件嵌套在语句事件中，语句事件嵌套在事务事件中。Within the event hierarchy, wait events nest within stage events, which nest within statement events, which nest within transaction events.

这些表存储阶段事件：These tables store stage events:

以下各节描述了阶段事件表。还有汇总表，用于聚合阶段事件的信息；请参见 第 29.12.20.2 节，“阶段汇总表”。The following sections describe the stage event tables. There are also summary tables that aggregate information about stage events; see Section 29.12.20.2, “Stage Summary Tables”.

有关三个阶段事件表之间关系的更多信息，请参见 第 29.9 节，“当前和历史事件的性能模式表”。For more information about the relationship between the three stage event tables, see Section 29.9, “Performance Schema Tables for Current and Historical Events”.

配置阶段事件收集Configuring Stage Event Collection

要控制是否收集阶段事件，请设置相关仪器和消费者的状态：To control whether to collect stage events, set the state of the relevant instruments and consumers:

除了那些提供语句进度信息的工具之外，阶段工具默认情况下是禁用的。例如：Other than those instruments that provide statement progress information, the stage instruments are disabled by default. For example:

mysql> SELECT NAME, ENABLED, TIMED
       FROM performance_schema.setup_instruments
       WHERE NAME RLIKE 'stage/sql/[a-c]';
+----------------------------------------------------+---------+-------+
| NAME                                               | ENABLED | TIMED |
+----------------------------------------------------+---------+-------+
| stage/sql/After create                             | NO      | NO    |
| stage/sql/allocating local table                   | NO      | NO    |
| stage/sql/altering table                           | NO      | NO    |
| stage/sql/committing alter table to storage engine | NO      | NO    |
| stage/sql/Changing master                          | NO      | NO    |
| stage/sql/Checking master version                  | NO      | NO    |
| stage/sql/checking permissions                     | NO      | NO    |
| stage/sql/cleaning up                              | NO      | NO    |
| stage/sql/closing tables                           | NO      | NO    |
| stage/sql/Connecting to master                     | NO      | NO    |
| stage/sql/converting HEAP to MyISAM                | NO      | NO    |
| stage/sql/Copying to group table                   | NO      | NO    |
| stage/sql/Copying to tmp table                     | NO      | NO    |
| stage/sql/copy to tmp table                        | NO      | NO    |
| stage/sql/Creating sort index                      | NO      | NO    |
| stage/sql/creating table                           | NO      | NO    |
| stage/sql/Creating tmp table                       | NO      | NO    |
+----------------------------------------------------+---------+-------+

提供语句进度信息的阶段事件工具默认情况下是启用并计时的：Stage event instruments that provide statement progress information are enabled and timed by default:

mysql> SELECT NAME, ENABLED, TIMED
       FROM performance_schema.setup_instruments
       WHERE ENABLED='YES' AND NAME LIKE "stage/%";
+------------------------------------------------------+---------+-------+
| NAME                                                 | ENABLED | TIMED |
+------------------------------------------------------+---------+-------+
| stage/sql/copy to tmp table                          | YES     | YES   |
| stage/sql/Applying batch of row changes (write)      | YES     | YES   |
| stage/sql/Applying batch of row changes (update)     | YES     | YES   |
| stage/sql/Applying batch of row changes (delete)     | YES     | YES   |
| stage/innodb/alter table (end)                       | YES     | YES   |
| stage/innodb/alter table (flush)                     | YES     | YES   |
| stage/innodb/alter table (insert)                    | YES     | YES   |
| stage/innodb/alter table (log apply index)           | YES     | YES   |
| stage/innodb/alter table (log apply table)           | YES     | YES   |
| stage/innodb/alter table (merge sort)                | YES     | YES   |
| stage/innodb/alter table (read PK and internal sort) | YES     | YES   |
| stage/innodb/buffer pool load                        | YES     | YES   |
| stage/innodb/clone (file copy)                       | YES     | YES   |
| stage/innodb/clone (redo copy)                       | YES     | YES   |
| stage/innodb/clone (page copy)                       | YES     | YES   |
+------------------------------------------------------+---------+-------+

阶段消费者默认情况下是禁用的：The stage consumers are disabled by default:

mysql> SELECT *
       FROM performance_schema.setup_consumers
       WHERE NAME LIKE 'events_stages%';
+----------------------------+---------+
| NAME                       | ENABLED |
+----------------------------+---------+
| events_stages_current      | NO      |
| events_stages_history      | NO      |
| events_stages_history_long | NO      |
+----------------------------+---------+

要在服务器启动时控制阶段事件收集，请在您的 my.cnf 文件中使用如下行：To control stage event collection at server startup, use lines like these in your my.cnf file:

要在运行时控制阶段事件收集，请更新 setup_instruments 和 setup_consumers 表：To control stage event collection at runtime, update the setup_instruments and setup_consumers tables:

要仅收集特定的阶段事件，请只启用相应的阶段工具。要仅收集特定阶段事件表的阶段事件，请启用阶段工具，但只启用与所需表对应的阶段消费者。To collect only specific stage events, enable only the corresponding stage instruments. To collect stage events only for specific stage event tables, enable the stage instruments but only the stage consumers corresponding to the desired tables.

有关配置事件收集的更多信息，请参见第 29.3 节，“性能模式启动配置”，以及第 29.4 节，“性能模式运行时配置”。For additional information about configuring event collection, see Section 29.3, “Performance Schema Startup Configuration”, and Section 29.4, “Performance Schema Runtime Configuration”.

阶段事件进度信息Stage Event Progress Information

Performance Schema 阶段事件表包含两列，结合起来可为每行提供阶段进度指示器：The Performance Schema stage event tables contain two columns that, taken together, provide a stage progress indicator for each row:

如果没有提供某个工具的信息，每一列都是NULL。如果信息可用，对其的解释完全依赖于工具的实现。性能模式表提供了存储进度数据的容器，但不对度量本身的语义做任何假设：Each column is NULL if no progress information is provided for an instrument. Interpretation of the information, if it is available, depends entirely on the instrument implementation. The Performance Schema tables provide a container to store progress data, but make no assumptions about the semantics of the metric itself:

阶段事件进度指示器的插装可以实现以下任何行为：Instrumentation for a stage event progress indicator can implement any of the following behaviors:

stage/sql/copy to tmp table 工具说明了进度指示器的工作原理。在执行 ALTER TABLE 语句时，会使用 stage/sql/copy to tmp table 阶段，根据要复制的数据量，这个阶段可能会执行很长时间。The stage/sql/copy to tmp table instrument illustrates how progress indicators work. During execution of an ALTER TABLE statement, the stage/sql/copy to tmp table stage is used, and this stage can execute potentially for a long time, depending on the size of the data to copy.

表复制任务有一个已定义的终止条件（所有行已复制），并且 stage/sql/copy to tmp table 阶段会提供有限的进度信息：所使用的工作单元是已复制的行数，WORK_COMPLETED 和 WORK_ESTIMATED 都是有意义的，它们的比值表示任务完成的百分比。The table-copy task has a defined termination (all rows copied), and the stage/sql/copy to tmp table stage is instrumented to provided bounded progress information: The work unit used is number of rows copied, WORK_COMPLETED and WORK_ESTIMATED are both meaningful, and their ratio indicates task percentage complete.

要启用该工具和相关的使用者，请执行以下语句：To enable the instrument and the relevant consumers, execute these statements:

UPDATE performance_schema.setup_instruments
SET ENABLED='YES'
WHERE NAME='stage/sql/copy to tmp table';

UPDATE performance_schema.setup_consumers
SET ENABLED='YES'
WHERE NAME LIKE 'events_stages_%';

要查看正在进行的 ALTER TABLE 语句的进度，请从 events_stages_current 表中进行选择。To see the progress of an ongoing ALTER TABLE statement, select from the events_stages_current table.