optimizer_trace：启用或禁用优化器跟踪。参见 第 10.15.8 节，“optimizer_trace 系统变量”。optimizer_trace: Enables or disables optimizer tracing. See Section 10.15.8, “The optimizer_trace System Variable”.

optimizer_trace_features：启用或禁用 MySQL 优化器的选定功能，使用此处显示的语法：optimizer_trace_features: Enables or disables selected features of the MySQL Optimizer, using the syntax shown here:

SET optimizer_trace_features=option=value[,option=value][,...]

option: 
  {greedy_search | range_optimizer | dynamic_range | repeated_subselect}

value:
  {on | off | default}

有关这些功能的效果的更多信息，请参见 第 10.15.10 节，“选择要跟踪的优化器功能”。See Section 10.15.10, “Selecting Optimizer Features to Trace”, for more information on the effects of these.

optimizer_trace_max_mem_size：用于存储所有跟踪的最大内存量。optimizer_trace_max_mem_size: Maximum amount of memory that can be used for storing all traces.

optimizer_trace_limit：要显示的优化器跟踪的最大数量。更多信息请参见第 10.15.4 节，“调整跟踪清理”。optimizer_trace_limit: The maximum number of optimizer traces to be shown. See Section 10.15.4, “Tuning Trace Purging”, for more information.

optimizer_trace_offset：显示的第一个跟踪的偏移量。请参见第 10.15.4 节，“调整跟踪清理”。optimizer_trace_offset: Offset of the first trace shown. See Section 10.15.4, “Tuning Trace Purging”.

end_markers_in_json：如果设置为 1，会导致在闭合括号附近重复显示键（如果存在）。这也会影响那些支持此语句的 MySQL 版本中 EXPLAIN FORMAT=JSON 的输出。参见 第 10.15.9 节，“end_markers_in_json 系统变量”。end_markers_in_json: If set to 1, causes the trace to repeat the key (if present) near the closing bracket. This also affects the output of EXPLAIN FORMAT=JSON in those versions of MySQL which support this statement. See Section 10.15.9, “The end_markers_in_json System Variable”.