MySQL :: MySQL 8.4 参考手册 :: 10.15.1 典型用法

MySQL 8.4 参考手册 · 中文镜像

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执行优化器跟踪包括以下步骤：To perform optimizer tracing entails the following steps:

通过执行 SET optimizer_trace="enabled=ON" 来启用跟踪。Enable tracing by executing SET optimizer_trace="enabled=ON".
执行需要跟踪的语句。请参阅第 10.15.3 节，“可跟踪语句”，了解可以跟踪的语句列表。Execute the statement to be traced. See Section 10.15.3, “Traceable Statements”, for a listing of statements which can be traced.
检查 INFORMATION_SCHEMA.OPTIMIZER_TRACE 表的内容。Examine the contents of the INFORMATION_SCHEMA.OPTIMIZER_TRACE table.
要检查多个查询的痕迹，请根据需要重复前两个步骤。To examine traces for multiple queries, repeat the previous two steps as needed.
完成后要禁用跟踪，请执行 SET optimizer_trace="enabled=OFF"。To disable tracing after you have finished, execute SET optimizer_trace="enabled=OFF".

您只能追踪当前会话中执行的语句；您无法查看其他会话的追踪。You can trace only statements which are executed within the current session; you cannot see traces from other sessions.