MySQL 8.4 Release Notes
optimizer_trace 系统变量具有这些开/关开关:The optimizer_trace system variable has these on/off switches:
enabled:启用(ON)或禁用(OFF)跟踪enabled: Enables (ON) or disables (OFF) tracingone_line:如果设置为ON,跟踪将不包含空白,从而节省空间。这会使人类难以阅读跟踪,但 JSON 解析器仍然可以使用,因为它们会忽略空白。one_line: If set toON, the trace contains no whitespace, thus conserving space. This renders the trace difficult to read for humans, still usable by JSON parsers, since they ignore whitespace.