[GitHub] [beam] damccorm commented on a change in pull request #16775: [BEAM-13803] Add support for native iterable side inputs to the Go SDK

[GitBox <gi...@apache.org>]

damccorm commented on a change in pull request #16775:
URL: https://github.com/apache/beam/pull/16775#discussion_r801914322



##########
File path: sdks/go/pkg/beam/core/runtime/exec/sideinput.go
##########
@@ -43,26 +43,71 @@ type sideInputAdapter struct {
 	kc          ElementEncoder
 	ec          ElementDecoder
 	wm          WindowMapper
+	c           *coder.Coder
 }
 
 // NewSideInputAdapter returns a side input adapter for the given StreamID and coder.
-// It expects a W<KV<K,V>> coder, because the protocol supports MultiSet access only.
+// It expects a W<V> or W<KV<K,V>> coder, because the protocol requires windowing information.
 func NewSideInputAdapter(sid StreamID, sideInputID string, c *coder.Coder, wm WindowMapper) SideInputAdapter {
-	if !coder.IsW(c) || !coder.IsKV(coder.SkipW(c)) {
-		panic(fmt.Sprintf("expected WKV coder for side input %v: %v", sid, c))
+	if !coder.IsW(c) {
+		panic(fmt.Sprintf("expected WV coder for side input %v: %v", sid, c))
 	}
 
 	wc := MakeWindowEncoder(c.Window)
-	kc := MakeElementEncoder(coder.SkipW(c).Components[0])
-	ec := MakeElementDecoder(coder.SkipW(c).Components[1])
-	return &sideInputAdapter{sid: sid, sideInputID: sideInputID, wc: wc, kc: kc, ec: ec, wm: wm}
+	var kc ElementEncoder
+	var ec ElementDecoder
+	if coder.IsKV(coder.SkipW(c)) {
+		kc = MakeElementEncoder(coder.SkipW(c).Components[0])
+		ec = MakeElementDecoder(coder.SkipW(c).Components[1])
+	} else {
+		ec = MakeElementDecoder(coder.SkipW(c))

Review comment:
       Could you help me understand why we need an encoder and decoder in the KV case, and just a decoder in this case (aka, please help Danny understand how we use Coders 😅)

##########
File path: sdks/go/pkg/beam/core/runtime/graphx/translate.go
##########
@@ -418,7 +379,7 @@ func (m *marshaller) addMultiEdge(edge NamedEdge) ([]string, error) {
 
 				si[fmt.Sprintf("i%v", i)] = &pipepb.SideInput{
 					AccessPattern: &pipepb.FunctionSpec{
-						Urn: URNMultimapSideInput,
+						Urn: URNIterableSideInput,
 					},
 					ViewFn: &pipepb.FunctionSpec{
 						Urn: "foo",

Review comment:
       I know this is coming from the MultiMap version of this, but what does `Urn: "foo"` actually do here? Is this doing something different than just leaving the ViewFn empty would?




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