lostluck commented on code in PR #27737:
URL: https://github.com/apache/beam/pull/27737#discussion_r1279435001
##########
sdks/go/pkg/beam/runners/prism/internal/handlerunner.go:
##########
@@ -63,13 +64,72 @@ func (*runner) ConfigCharacteristic() reflect.Type {
return reflect.TypeOf((*RunnerCharacteristic)(nil)).Elem()
}
+var _ transformPreparer = (*runner)(nil)
+
+func (*runner) PrepareUrns() []string {
+ return []string{urns.TransformReshuffle}
+}
+
+// PrepareTransform handles special processing with respect runner transforms,
like reshuffle.
+func (h *runner) PrepareTransform(tid string, t *pipepb.PTransform, comps
*pipepb.Components) (*pipepb.Components, []string) {
+ // TODO: Implement the windowing strategy the "backup" transforms used
for Reshuffle.
+ // TODO: Implement a fusion break for reshuffles.
+
+ if h.config.SDKReshuffle {
+ panic("SDK side reshuffle not yet supported")
+ }
+
+ // A Reshuffle, in principle, is a no-op on the pipeline structure, WRT
correctness.
+ // It could however affect performance, so it exists to tell the runner
that this
+ // point in the pipeline needs a fusion break, to enable the pipeline
to change it's
+ // degree of parallelism.
+ //
+ // The change of parallelism goes both ways. It could allow for larger
batch sizes
+ // enable smaller batch sizes downstream if it is infact paralleizable.
+ //
+ // But for a single transform node per stage runner, we can elide it
entirely,
+ // since the input collection and output collection types match.
+
+ // Get the input and output PCollections, there should only be 1 each.
+ if len(t.GetOutputs()) != 1 {
+ panic("Expected single putput PCollection in reshuffle: " +
prototext.Format(t))
+ }
+ if len(t.GetOutputs()) != 1 {
+ panic("Expected single putput PCollection in reshuffle: " +
prototext.Format(t))
+ }
Review Comment:
lol. putput. Good catch!
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