performance_schema

此变量的值为 ON 或 OFF，用于指示 Performance Schema 是否启用。默认情况下，值为 ON。在服务器启动时，可以指定此变量而不赋值，或赋值为 ON 或 1 以启用它，或者赋值为 OFF 或 0 以禁用它。The value of this variable is ON or OFF to indicate whether the Performance Schema is enabled. By default, the value is ON. At server startup, you can specify this variable with no value or a value of ON or 1 to enable it, or with a value of OFF or 0 to disable it.

即使性能模式（Performance Schema）被禁用，它仍然会继续填充 global_variables、session_variables、global_status 和 session_status 表。这样做是为了在必要时允许通过这些表获取 SHOW VARIABLES 和 SHOW STATUS 语句的结果。当禁用时，性能模式还会填充部分复制表。Even when the Performance Schema is disabled, it continues to populate the global_variables, session_variables, global_status, and session_status tables. This occurs as necessary to permit the results for the SHOW VARIABLES and SHOW STATUS statements to be drawn from those tables. The Performance Schema also populates some of the replication tables when disabled.

performance_schema_accounts_size

accounts 表中的行数。如果该变量为 0，Performance Schema 不会在 accounts 表中维护连接统计信息，也不会在 status_by_account 表中维护状态变量信息。The number of rows in the accounts table. If this variable is 0, the Performance Schema does not maintain connection statistics in the accounts table or status variable information in the status_by_account table.

performance_schema_digests_size

events_statements_summary_by_digest 表中的最大行数。如果超过此最大值，导致某个摘要无法被检测，Performance Schema 会增加 Performance_schema_digest_lost 状态变量。The maximum number of rows in the events_statements_summary_by_digest table. If this maximum is exceeded such that a digest cannot be instrumented, the Performance Schema increments the Performance_schema_digest_lost status variable.

有关语句摘要的更多信息，请参见 第 29.10 节，“Performance Schema 语句摘要与采样”。For more information about statement digesting, see Section 29.10, “Performance Schema Statement Digests and Sampling”.

performance_schema_error_size

已记录的服务器错误代码数量。默认值为实际的服务器错误代码数量。虽然该值可以设置在 0 到最大值之间，但预期用途是将其设置为默认值（记录所有错误）或 0（不记录任何错误）。The number of instrumented server error codes. The default value is the actual number of server error codes. Although the value can be set anywhere from 0 to its maximum, the intended use is to set it to either its default (to instrument all errors) or 0 (to instrument no errors).

错误信息汇总在摘要表中；请参见 第 29.12.20.11 节，“错误摘要表”。如果发生未被监控的错误，该错误的相关信息将汇总到每个摘要表中的 NULL 行；也就是说，汇总到 ERROR_NUMBER=0、ERROR_NAME=NULL 和 SQLSTATE=NULL 的行。Error information is aggregated in summary tables; see Section 29.12.20.11, “Error Summary Tables”. If an error occurs that is not instrumented, information for the occurrence is aggregated to the NULL row in each summary table; that is, to the row with ERROR_NUMBER=0, ERROR_NAME=NULL, and SQLSTATE=NULL.

performance_schema_events_stages_history_long_size

events_stages_history_long 表中的行数。The number of rows in the events_stages_history_long table.

performance_schema_events_stages_history_size

events_stages_history 表中每个线程的行数。The number of rows per thread in the events_stages_history table.

performance_schema_events_statements_history_long_size

events_statements_history_long 表中的行数。The number of rows in the events_statements_history_long table.

performance_schema_events_statements_history_size

在 events_statements_history 表中，每个线程的行数。The number of rows per thread in the events_statements_history table.

performance_schema_events_transactions_history_long_size

events_transactions_history_long 表中的行数。The number of rows in the events_transactions_history_long table.

performance_schema_events_transactions_history_size

每个线程在 events_transactions_history 表中的行数。The number of rows per thread in the events_transactions_history table.

performance_schema_events_waits_history_long_size

events_waits_history_long 表中的行数。The number of rows in the events_waits_history_long table.

performance_schema_events_waits_history_size

events_waits_history 表中每个线程的行数。The number of rows per thread in the events_waits_history table.

performance_schema_hosts_size

hosts 表中的行数。如果该变量为 0，Performance Schema 将不会在 hosts 表中维护连接统计信息，也不会在 status_by_host 表中维护状态变量信息。The number of rows in the hosts table. If this variable is 0, the Performance Schema does not maintain connection statistics in the hosts table or status variable information in the status_by_host table.

performance_schema_max_cond_classes

条件工具的最大数量。有关如何设置和使用此变量的信息，请参见 第 29.7 节，“性能模式状态监控”。The maximum number of condition instruments. For information about how to set and use this variable, see Section 29.7, “Performance Schema Status Monitoring”.

performance_schema_max_cond_instances

仪器化条件对象的最大数量。有关如何设置和使用此变量的信息，请参阅 第 29.7 节，“性能模式状态监控”。The maximum number of instrumented condition objects. For information about how to set and use this variable, see Section 29.7, “Performance Schema Status Monitoring”.

performance_schema_max_digest_length

在 Performance Schema 中，为计算标准化语句摘要值，每条语句保留的最大内存字节数。此变量与 max_digest_length 有关；请参阅第 7.1.8 节，“服务器系统变量” 中该变量的描述。The maximum number of bytes of memory reserved per statement for computation of normalized statement digest values in the Performance Schema. This variable is related to max_digest_length; see the description of that variable in Section 7.1.8, “Server System Variables”.

有关语句消化的更多信息，包括内存使用方面的考虑，请参见 第 29.10 节，“性能模式语句消化和采样”。For more information about statement digesting, including considerations regarding memory use, see Section 29.10, “Performance Schema Statement Digests and Sampling”.

performance_schema_max_digest_sample_age

该变量影响 events_statements_summary_by_digest 表的语句采样。当插入新的表行时，生成该行 digest 值的语句会被存储为与该 digest 关联的当前样本语句。此后，当服务器看到具有相同 digest 值的其他语句时，它会决定是否使用新语句替换当前样本语句（即是否重新采样）。重新采样策略基于当前样本语句和新语句的比较等待时间，并可选择考虑当前样本语句的存留时间：This variable affects statement sampling for the events_statements_summary_by_digest table. When a new table row is inserted, the statement that produced the row digest value is stored as the current sample statement associated with the digest. Thereafter, when the server sees other statements with the same digest value, it determines whether to use the new statement to replace the current sample statement (that is, whether to resample). Resampling policy is based on the comparative wait times of the current sample statement and new statement and, optionally, the age of the current sample statement:

有关语句采样的信息，请参见 第 29.10 节，“性能模式语句摘要与采样”。For information about statement sampling, see Section 29.10, “Performance Schema Statement Digests and Sampling”.

performance_schema_max_file_classes

文件工具的最大数量。有关如何设置和使用此变量的信息，请参阅 第 29.7 节，“性能模式状态监控”。The maximum number of file instruments. For information about how to set and use this variable, see Section 29.7, “Performance Schema Status Monitoring”.

performance_schema_max_file_handles

最大打开的文件对象数量。有关如何设置和使用此变量的信息，请参阅 第 29.7 节，“性能模式状态监控”。The maximum number of opened file objects. For information about how to set and use this variable, see Section 29.7, “Performance Schema Status Monitoring”.

performance_schema_max_file_handles 的值应大于 open_files_limit 的值：open_files_limit 影响服务器可以支持的最大打开文件句柄数，而 performance_schema_max_file_handles 影响这些文件句柄中可被监测的数量。The value of performance_schema_max_file_handles should be greater than the value of open_files_limit: open_files_limit affects the maximum number of open file handles the server can support and performance_schema_max_file_handles affects how many of these file handles can be instrumented.

performance_schema_max_file_instances

可检测文件对象的最大数量。有关如何设置和使用此变量的信息，请参见 第 29.7 节，“性能模式状态监控”。The maximum number of instrumented file objects. For information about how to set and use this variable, see Section 29.7, “Performance Schema Status Monitoring”.

performance_schema_max_index_stat

Performance Schema 为其维护统计信息的最大索引数量。如果超过此最大值以至于索引统计信息丢失，Performance Schema 将增加 Performance_schema_index_stat_lost 状态变量。默认值使用 performance_schema_max_table_instances 的值自动确定。The maximum number of indexes for which the Performance Schema maintains statistics. If this maximum is exceeded such that index statistics are lost, the Performance Schema increments the Performance_schema_index_stat_lost status variable. The default value is autosized using the value of performance_schema_max_table_instances.

performance_schema_max_memory_classes

内存工具的最大数量。有关如何设置和使用此变量的信息，请参见 第 29.7 节，“性能模式状态监控”。The maximum number of memory instruments. For information about how to set and use this variable, see Section 29.7, “Performance Schema Status Monitoring”.

performance_schema_max_metadata_locks

元数据锁定工具的最大数量。此值控制metadata_locks 表的大小。如果超过此最大值以至于无法对元数据锁进行监控，Performance Schema 将增加Performance_schema_metadata_lock_lost 状态变量。The maximum number of metadata lock instruments. This value controls the size of the metadata_locks table. If this maximum is exceeded such that a metadata lock cannot be instrumented, the Performance Schema increments the Performance_schema_metadata_lock_lost status variable.

performance_schema_max_meter_classes

可以创建的计量仪器的最大数量Maximum number of meter instruments which can be created

performance_schema_max_metric_classes

可以创建的最大指标工具数量。Maximum number of metric instruments which can be created.

performance_schema_max_mutex_classes

互斥体工具的最大数量。有关如何设置和使用此变量的信息，请参见 第 29.7 节，“性能模式状态监控”。The maximum number of mutex instruments. For information about how to set and use this variable, see Section 29.7, “Performance Schema Status Monitoring”.

performance_schema_max_mutex_instances

可监控的互斥体对象的最大数量。有关如何设置和使用此变量的信息，请参见 第 29.7 节，“性能模式状态监控”。The maximum number of instrumented mutex objects. For information about how to set and use this variable, see Section 29.7, “Performance Schema Status Monitoring”.

performance_schema_max_prepared_statements_instances

prepared_statements_instances 表中的最大行数。如果超过此最大值，导致某个预准备语句无法被监控，Performance Schema 会增加 Performance_schema_prepared_statements_lost 状态变量。有关如何设置和使用此变量的信息，请参见 第 29.7 节，“Performance Schema 状态监控”。The maximum number of rows in the prepared_statements_instances table. If this maximum is exceeded such that a prepared statement cannot be instrumented, the Performance Schema increments the Performance_schema_prepared_statements_lost status variable. For information about how to set and use this variable, see Section 29.7, “Performance Schema Status Monitoring”.

该变量的默认值根据 max_prepared_stmt_count 系统变量的值自动调整。The default value of this variable is autosized based on the value of the max_prepared_stmt_count system variable.

performance_schema_max_rwlock_classes

rwlock 工具的最大数量。有关如何设置和使用此变量的信息，请参见 第 29.7 节，“Performance Schema 状态监控”。The maximum number of rwlock instruments. For information about how to set and use this variable, see Section 29.7, “Performance Schema Status Monitoring”.

performance_schema_max_program_instances

Performance Schema 为其维护统计信息的最大存储程序数量。如果超过此最大值，Performance Schema 会增加 Performance_schema_program_lost 状态变量。有关如何设置和使用此变量的信息，请参阅 第 29.7 节，“Performance Schema 状态监控”。The maximum number of stored programs for which the Performance Schema maintains statistics. If this maximum is exceeded, the Performance Schema increments the Performance_schema_program_lost status variable. For information about how to set and use this variable, see Section 29.7, “Performance Schema Status Monitoring”.

performance_schema_max_rwlock_instances

可监控的最大读写锁对象数量。有关如何设置和使用此变量的信息，请参阅 第 29.7 节，“Performance Schema 状态监控”。The maximum number of instrumented rwlock objects. For information about how to set and use this variable, see Section 29.7, “Performance Schema Status Monitoring”.

performance_schema_max_socket_classes

套接字工具的最大数量。有关如何设置和使用此变量的信息，请参阅第 29.7 节，“性能模式状态监控”。The maximum number of socket instruments. For information about how to set and use this variable, see Section 29.7, “Performance Schema Status Monitoring”.

performance_schema_max_socket_instances

可检测的套接字对象的最大数量。有关如何设置和使用此变量的信息，请参见 第 29.7 节，“性能模式状态监控”。The maximum number of instrumented socket objects. For information about how to set and use this variable, see Section 29.7, “Performance Schema Status Monitoring”.

performance_schema_max_sql_text_length

用于存储 SQL 语句的最大字节数。该值适用于以下列所需的存储：The maximum number of bytes used to store SQL statements. The value applies to storage required for these columns:

超过 performance_schema_max_sql_text_length 的字节将被丢弃，并且不会出现在该列中。在该列中，仅在前面这么多字节之后不同的语句将无法区分。Any bytes in excess of performance_schema_max_sql_text_length are discarded and do not appear in the column. Statements differing only after that many initial bytes are indistinguishable in the column.

降低 performance_schema_max_sql_text_length 的值可以减少内存使用，但如果 SQL 语句仅在末尾不同，会导致更多语句无法区分。增加该值会增加内存使用，但允许区分更长的语句。Decreasing the performance_schema_max_sql_text_length value reduces memory use but causes more statements to become indistinguishable if they differ only at the end. Increasing the value increases memory use but permits longer statements to be distinguished.

performance_schema_max_stage_classes

舞台仪器的最大数量。有关如何设置和使用此变量的信息，请参见 第 29.7 节，“Performance Schema 状态监控”。The maximum number of stage instruments. For information about how to set and use this variable, see Section 29.7, “Performance Schema Status Monitoring”.

performance_schema_max_statement_classes

语句工具的最大数量。有关如何设置和使用此变量的信息，请参见 第 29.7 节，“Performance Schema 状态监控”。The maximum number of statement instruments. For information about how to set and use this variable, see Section 29.7, “Performance Schema Status Monitoring”.

默认值是在服务器构建时根据客户端/服务器协议中的命令数量以及服务器支持的 SQL 语句类型数量计算得出的。The default value is calculated at server build time based on the number of commands in the client/server protocol and the number of SQL statement types supported by the server.

除非将其设置为 0 以禁用所有语句工具并节省所有相关内存，否则不应更改此变量。将该变量设置为除默认值之外的非零值没有任何好处；特别是，设置值大于默认值会导致分配比实际需要更多的内存。This variable should not be changed, unless to set it to 0 to disable all statement instrumentation and save all memory associated with it. Setting the variable to nonzero values other than the default has no benefit; in particular, values larger than the default cause more memory to be allocated then is needed.

performance_schema_max_statement_stack

Performance Schema 维护统计信息的嵌套存储程序调用的最大深度。当超过此最大值时，Performance Schema 会针对每个执行的存储程序语句递增 Performance_schema_nested_statement_lost 状态变量。The maximum depth of nested stored program calls for which the Performance Schema maintains statistics. When this maximum is exceeded, the Performance Schema increments the Performance_schema_nested_statement_lost status variable for each stored program statement executed.

performance_schema_max_table_handles

打开的表对象的最大数量。此值控制 table_handles 表的大小。如果超过此最大值，导致某个表句柄无法被记录，性能模式会增加 Performance_schema_table_handles_lost 状态变量。有关如何设置和使用此变量的信息，请参阅 第 29.7 节，“性能模式状态监控”。The maximum number of opened table objects. This value controls the size of the table_handles table. If this maximum is exceeded such that a table handle cannot be instrumented, the Performance Schema increments the Performance_schema_table_handles_lost status variable. For information about how to set and use this variable, see Section 29.7, “Performance Schema Status Monitoring”.

performance_schema_max_table_instances

可检测表对象的最大数量。有关如何设置和使用此变量的信息，请参见 第 29.7 节，“性能模式状态监测”。The maximum number of instrumented table objects. For information about how to set and use this variable, see Section 29.7, “Performance Schema Status Monitoring”.

performance_schema_max_table_lock_stat

Performance Schema 维护锁统计信息的最大表数量。如果超过此最大值而导致表锁统计信息丢失，Performance Schema 会增加Performance_schema_table_lock_stat_lost状态变量。The maximum number of tables for which the Performance Schema maintains lock statistics. If this maximum is exceeded such that table lock statistics are lost, the Performance Schema increments the Performance_schema_table_lock_stat_lost status variable.

performance_schema_max_thread_classes

线程工具的最大数量。有关如何设置和使用此变量的信息，请参见 第 29.7 节，“Performance Schema 状态监控”。The maximum number of thread instruments. For information about how to set and use this variable, see Section 29.7, “Performance Schema Status Monitoring”.

performance_schema_max_thread_instances

可监控的线程对象的最大数量。该值控制threads表的大小。如果超过该最大值而无法对线程进行监控，Performance Schema 将增加Performance_schema_thread_instances_lost状态变量。有关如何设置和使用此变量的信息，请参见第 29.7 节，“Performance Schema 状态监控”。The maximum number of instrumented thread objects. The value controls the size of the threads table. If this maximum is exceeded such that a thread cannot be instrumented, the Performance Schema increments the Performance_schema_thread_instances_lost status variable. For information about how to set and use this variable, see Section 29.7, “Performance Schema Status Monitoring”.

max_connections 系统变量影响服务器中可以运行的线程数量。performance_schema_max_thread_instances 影响这些正在运行的线程中可以被检测的数量。The max_connections system variable affects how many threads can run in the server. performance_schema_max_thread_instances affects how many of these running threads can be instrumented.

variables_by_thread 和 status_by_thread 表仅包含关于前台线程的系统和状态变量信息。如果并非所有线程都被 Performance Schema 仪表化，则该表会缺少一些行。在这种情况下，Performance_schema_thread_instances_lost 状态变量大于零。The variables_by_thread and status_by_thread tables contain system and status variable information only about foreground threads. If not all threads are instrumented by the Performance Schema, this table misses some rows. In this case, the Performance_schema_thread_instances_lost status variable is greater than zero.

performance_schema_session_connect_attrs_size

为每个线程预分配的内存量，用于保存连接属性的键值对。如果客户端发送的连接属性数据总大小大于此数量，Performance Schema 会截断属性数据，增加 Performance_schema_session_connect_attrs_lost 状态变量，并在 log_error_verbosity 系统变量值大于 1 时在错误日志中写入截断发生的消息。如果属性缓冲区有足够空间，还会向会话属性中添加一个 _truncated 属性，其值指示丢失了多少字节。这使得 Performance Schema 能够在连接属性表中暴露每个连接的截断信息，而无需检查错误日志即可查看这些信息。The amount of preallocated memory per thread reserved to hold connection attribute key-value pairs. If the aggregate size of connection attribute data sent by a client is larger than this amount, the Performance Schema truncates the attribute data, increments the Performance_schema_session_connect_attrs_lost status variable, and writes a message to the error log indicating that truncation occurred if the log_error_verbosity system variable is greater than 1. A _truncated attribute is also added to the session attributes with a value indicating how many bytes were lost, if the attribute buffer has sufficient space. This enables the Performance Schema to expose per-connection truncation information in the connection attribute tables. This information can be examined without having to check the error log.

performance_schema_session_connect_attrs_size 的默认值在服务器启动时会自动调整大小。这个值可能较小，因此如果发生截断（Performance_schema_session_connect_attrs_lost 变为非零），您可能希望将 performance_schema_session_connect_attrs_size 显式设置为更大的值。The default value of performance_schema_session_connect_attrs_size is autosized at server startup. This value may be small, so if truncation occurs (Performance_schema_session_connect_attrs_lost becomes nonzero), you may wish to set performance_schema_session_connect_attrs_size explicitly to a larger value.

虽然允许的最大 performance_schema_session_connect_attrs_size 值为 1MB，但有效最大值为 64KB，因为服务器对接受的连接属性数据的总大小施加了 64KB 的限制。如果客户端尝试发送超过 64KB 的属性数据，服务器将拒绝连接。更多信息，请参见 第 29.12.9 节，“Performance Schema 连接属性表”。Although the maximum permitted performance_schema_session_connect_attrs_size value is 1MB, the effective maximum is 64KB because the server imposes a limit of 64KB on the aggregate size of connection attribute data it accepts. If a client attempts to send more than 64KB of attribute data, the server rejects the connection. For more information, see Section 29.12.9, “Performance Schema Connection Attribute Tables”.

performance_schema_setup_actors_size

setup_actors 表中的行数。The number of rows in the setup_actors table.

performance_schema_setup_objects_size

setup_objects 表中的行数。The number of rows in the setup_objects table.

performance_schema_show_processlist

SHOW PROCESSLIST 语句通过收集所有活动线程的数据提供进程信息。performance_schema_show_processlist 变量决定使用哪种 SHOW PROCESSLIST 实现：The SHOW PROCESSLIST statement provides process information by collecting thread data from all active threads. The performance_schema_show_processlist variable determines which SHOW PROCESSLIST implementation to use:

要启用替代实现，请启用 performance_schema_show_processlist 系统变量。为了确保默认实现和替代实现提供相同的信息，必须满足某些配置要求；请参见 第 29.12.22.7 节，“processlist 表”。To enable the alternative implementation, enable the performance_schema_show_processlist system variable. To ensure that the default and alternative implementations yield the same information, certain configuration requirements must be met; see Section 29.12.22.7, “The processlist Table”.

performance_schema_users_size

users 表中的行数。如果该变量为 0，Performance Schema 将不会在 users 表中维护连接统计信息，也不会在 status_by_user 表中维护状态变量信息。The number of rows in the users table. If this variable is 0, the Performance Schema does not maintain connection statistics in the users table or status variable information in the status_by_user table.