const TiDBTrace = "tr"
TiDBTrace is set as Baggage on traces which are used for tidb tracing.
ChildSpanFromContxt return a non-nil span. If span can be got from ctx, then returned span is a child of such span. Otherwise, returned span is a noop span.
NewRecordedTrace returns a Span which records directly via the specified callback.
SpanFromContext returns the span obtained from the context or, if none is found, a new one started through tracer.
A CallbackRecorder immediately invokes itself on received trace spans.
RecordSpan implements basictracer.SpanRecorder.