MySQL Internals Manual  /  Tracing the Optimizer  /  The optimizer_trace System Variable

8.10 The optimizer_trace System Variable

The optimizer_trace system variable has these on/off switches:

  • enabled: allows to enable/disable tracing

  • one_line: if on, the trace will have no whitespace; it's unreadable for humans but readable for JSON parsers (they ignore whitespace); the only advantage is a saving on space.