tracing: remove WithSeparateRecording

`WithSeparateRecording` set up a Span to *not* share its recording
with its parent. This was necessary before cockroachdb#50914 as parents would also
show up in children's recording, and SQL SpanStats want to set up spans
only for the purpose of populating them with the stats (and want to
avoid pulling a possibly giant recording of the parent out with it).

PR cockroachdb#50914 introduced the unidirectional transitivity we have today: a
parent's recording will recurse into the child, but not vice versa.
This means that the existing uses of `WithSeparateRecording` were no
longer useful; all they were doing was to hide information from the
parent.
In fact, they are counterproductive, as they prevent the full recording
to become available at the root span, which is not an issue today since
the only thing missing are SpanStats, but with always-on tracing we'd
possibly silently drop metadata.

Release note: None

pkg/sql/colflow/vectorized_flow.go

@@ -912,9 +912,8 @@ func (s *vectorizedFlowCreator) setupOutput(
 				metadataSourcesQueue,
 				execinfrapb.CallbackMetadataSource{
 					DrainMetaCb: func(ctx context.Context) []execinfrapb.ProducerMetadata {
-						// Start a separate recording so that GetRecording will return
-						// the recordings for only the child spans containing stats.
-						ctx, span := tracing.ChildSpanSeparateRecording(ctx, "")
+						// Start a child span whose recording will only contain SpanStats.
+						ctx, span := tracing.ChildSpan(ctx, "stats")
 						finishVectorizedStatsCollectors(
 							ctx, flowCtx.ID, flowCtx.Cfg.TestingKnobs.DeterministicStats, vscs,
 						)

pkg/sql/execinfra/processorsbase.go

@@ -849,7 +849,7 @@ func (pb *ProcessorBase) AppendTrailingMeta(meta execinfrapb.ProducerMetadata) {
 // ProcessorSpan creates a child span for a processor (if we are doing any
 // tracing). The returned span needs to be finished using tracing.FinishSpan.
 func ProcessorSpan(ctx context.Context, name string) (context.Context, *tracing.Span) {
-	return tracing.ChildSpanSeparateRecording(ctx, name)
+	return tracing.ChildSpan(ctx, name)
 }
 
 // StartInternal prepares the ProcessorBase for execution. It returns the

pkg/util/tracing/span.go

@@ -210,16 +210,12 @@ func (s *Span) IsRecording() bool {
 //
 // If parent != nil, the Span will be registered as a child of the respective
 // parent.
-// If separate recording is specified, the child is not registered with the
-// parent. Thus, the parent's recording will not include this child.
-func (s *crdbSpan) enableRecording(
-	parent *crdbSpan, recType RecordingType, separateRecording bool,
-) {
+func (s *crdbSpan) enableRecording(parent *crdbSpan, recType RecordingType) {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 	atomic.StoreInt32(&s.recording, 1)
 	s.mu.recording.recordingType = recType
-	if parent != nil && !separateRecording {
+	if parent != nil {
 		parent.addChild(s)
 	}
 	if recType == SnowballRecording {
@@ -256,7 +252,7 @@ func (s *Span) StartRecording(recType RecordingType) {
 	// If we're already recording (perhaps because the parent was recording when
 	// this Span was created), there's nothing to do.
 	if !s.crdb.isRecording() {
-		s.crdb.enableRecording(nil /* parent */, recType, false /* separateRecording */)
+		s.crdb.enableRecording(nil /* parent */, recType)
 	}
 }
 

pkg/util/tracing/span_options.go

@@ -183,18 +183,3 @@ func (forceRealSpanOption) apply(opts spanOptions) spanOptions {
 	opts.ForceRealSpan = true
 	return opts
 }
-
-type withSeparateRecordingOpt struct{}
-
-// WithSeparateRecording instructs StartSpan to configure any child span
-// started via WithParent to *not* share the recording with that parent.
-//
-// See WithParent and WithRemoteParent for details about recording inheritance.
-func WithSeparateRecording() SpanOption {
-	return withSeparateRecordingOpt{}
-}
-
-func (o withSeparateRecordingOpt) apply(opts spanOptions) spanOptions {
-	opts.SeparateRecording = true
-	return opts
-}

pkg/util/tracing/tracer.go

@@ -267,7 +267,7 @@ func (t *Tracer) startSpanGeneric(opName string, opts spanOptions) *Span {
 		if opts.Parent != nil {
 			p = &opts.Parent.crdb
 		}
-		s.crdb.enableRecording(p, recordingType, opts.SeparateRecording)
+		s.crdb.enableRecording(p, recordingType)
 	}
 
 	if t.useNetTrace() {
@@ -503,12 +503,6 @@ func ChildSpan(ctx context.Context, opName string) (context.Context, *Span) {
 	return childSpan(ctx, opName, spanOptions{})
 }
 
-// ChildSpanSeparateRecording is like ChildSpan but the new Span has separate
-// recording (see StartChildSpan).
-func ChildSpanSeparateRecording(ctx context.Context, opName string) (context.Context, *Span) {
-	return childSpan(ctx, opName, spanOptions{SeparateRecording: true})
-}
-
 func childSpan(ctx context.Context, opName string, opts spanOptions) (context.Context, *Span) {
 	sp := SpanFromContext(ctx)
 	if sp == nil || sp.isNoop() {

pkg/util/tracing/tracer_test.go

@@ -144,11 +144,12 @@ func TestStartChildSpan(t *testing.T) {
 
 	sp1 = tr.StartSpan("parent", WithForceRealSpan())
 	sp1.StartRecording(SingleNodeRecording)
-	sp2 = tr.StartSpan("child", WithParent(sp1), WithSeparateRecording())
+	sp2 = tr.StartSpan("child", WithParent(sp1))
 	sp2.Finish()
 	sp1.Finish()
 	if err := TestingCheckRecordedSpans(sp1.GetRecording(), `
 		Span parent:
+		Span child:
 	`); err != nil {
 		t.Fatal(err)
 	}