[GitHub] [beam] youngoli commented on a change in pull request #14192: [BEAM-9615] Embedded structs and Deterministic map encoding, and Logical Types.

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

youngoli commented on a change in pull request #14192:
URL: https://github.com/apache/beam/pull/14192#discussion_r593553104



##########
File path: sdks/go/pkg/beam/core/runtime/graphx/schema/schema.go
##########
@@ -280,82 +301,194 @@ func (r *Registry) FromType(ot reflect.Type) (*pipepb.Schema, error) {
 	return r.fromType(ot)
 }
 
+func (r *Registry) logicalTypeToFieldType(t reflect.Type) (*pipepb.FieldType, string, error) {
+	// Check if a logical type was registered that matches this struct type directly
+	// and if so, extract the schema from it for use.
+	if lID, ok := r.logicalTypeIdentifiers[t]; ok {
+		lt := r.logicalTypes[lID]
+		ftype, err := r.reflectTypeToFieldType(lt.StorageType())
+		if err != nil {
+			return nil, "", errors.Wrapf(err, "unable to convert LogicalType[%v]'s storage type %v for Go type of %v to a schema", lID, lt.StorageType(), lt.GoType())
+		}
+		return ftype, lID, nil
+	}
+	for _, lti := range r.logicalTypeInterfaces {
+		if !t.Implements(lti) {
+			continue
+		}
+		p := r.logicalTypeProviders[lti]
+		st, err := p(t)
+		if err != nil {
+			return nil, "", errors.Wrapf(err, "unable to convert LogicalType[%v] using provider for %v schema field", t, lti)
+		}
+		if st == nil {
+			continue
+		}
+		ftype, err := r.reflectTypeToFieldType(st)
+		if err != nil {
+			return nil, "", errors.Wrapf(err, "unable to convert LogicalType[%v]'s storage type %v for Go type of %v to a schema", "interface", st, t)
+		}
+		return ftype, t.String(), nil
+	}
+	return nil, "", nil
+}
+
 func (r *Registry) fromType(ot reflect.Type) (*pipepb.Schema, error) {
-	if reflectx.SkipPtr(ot).Kind() != reflect.Struct {
-		return nil, errors.Errorf("cannot convert %v to schema. FromType only converts structs to schemas", ot)
+	if schm, ok := r.typeToSchema[ot]; ok {
+		return schm, nil
 	}
-	schm, err := r.structToSchema(ot)
+	ftype, lID, err := r.logicalTypeToFieldType(ot)
 	if err != nil {
 		return nil, err
 	}
-	if ot.Kind() == reflect.Ptr {
-		schm.Options = append(schm.Options, &pipepb.Option{
-			Name: optGoNillable,
-		})
+	if ftype != nil {

Review comment:
       I notice the beginning of `structToSchema` is very similar to this section of `fromType`, and it gets called right after this section anyway. Is there a reason this needs to be here instead of just calling `structToSchema` right away? (If so it might be good to leave a comment explaining it)

##########
File path: sdks/go/pkg/beam/core/graph/coder/row_decoder.go
##########
@@ -114,16 +114,38 @@ func (b *RowDecoderBuilder) decoderForType(t reflect.Type) (func(io.Reader) (int
 // decoderForStructReflect returns a reflection based decoder function for the
 // given struct type.
 func (b *RowDecoderBuilder) decoderForStructReflect(t reflect.Type) (func(reflect.Value, io.Reader) error, error) {
-
 	var coder typeDecoderReflect
 	coder.typ = t
 	for i := 0; i < t.NumField(); i++ {
 		i := i // avoid alias issues in the closures.
 		sf := t.Field(i)
 		isUnexported := sf.PkgPath != ""
-		if isUnexported {
+		if sf.Anonymous {
+			ft := sf.Type
+			if ft.Kind() == reflect.Ptr {
+				// If a struct embeds a pointer to an unexported type,
+				// it is not possible to set a newly allocated value
+				// since the field is unexported.
+				//
+				// See https://golang.org/issue/21357
+				//
+				// Since the values are created by this package reflectively,
+				// there's no work around like pre-allocating the field
+				// manually.
+				if isUnexported {

Review comment:
       Does `isUnexported` describe whether the field itself is unexported? Or whether the type of the field is unexported? I thought it was the first, but based on this line and the comment you added at line 144, it's actually the second one. Is that right?

##########
File path: sdks/go/pkg/beam/core/runtime/graphx/schema/schema.go
##########
@@ -280,82 +301,194 @@ func (r *Registry) FromType(ot reflect.Type) (*pipepb.Schema, error) {
 	return r.fromType(ot)
 }
 
+func (r *Registry) logicalTypeToFieldType(t reflect.Type) (*pipepb.FieldType, string, error) {
+	// Check if a logical type was registered that matches this struct type directly
+	// and if so, extract the schema from it for use.
+	if lID, ok := r.logicalTypeIdentifiers[t]; ok {
+		lt := r.logicalTypes[lID]
+		ftype, err := r.reflectTypeToFieldType(lt.StorageType())
+		if err != nil {
+			return nil, "", errors.Wrapf(err, "unable to convert LogicalType[%v]'s storage type %v for Go type of %v to a schema", lID, lt.StorageType(), lt.GoType())
+		}
+		return ftype, lID, nil
+	}
+	for _, lti := range r.logicalTypeInterfaces {
+		if !t.Implements(lti) {
+			continue
+		}
+		p := r.logicalTypeProviders[lti]
+		st, err := p(t)
+		if err != nil {
+			return nil, "", errors.Wrapf(err, "unable to convert LogicalType[%v] using provider for %v schema field", t, lti)
+		}
+		if st == nil {
+			continue
+		}
+		ftype, err := r.reflectTypeToFieldType(st)
+		if err != nil {
+			return nil, "", errors.Wrapf(err, "unable to convert LogicalType[%v]'s storage type %v for Go type of %v to a schema", "interface", st, t)
+		}
+		return ftype, t.String(), nil
+	}
+	return nil, "", nil
+}
+
 func (r *Registry) fromType(ot reflect.Type) (*pipepb.Schema, error) {
-	if reflectx.SkipPtr(ot).Kind() != reflect.Struct {
-		return nil, errors.Errorf("cannot convert %v to schema. FromType only converts structs to schemas", ot)
+	if schm, ok := r.typeToSchema[ot]; ok {
+		return schm, nil
 	}
-	schm, err := r.structToSchema(ot)
+	ftype, lID, err := r.logicalTypeToFieldType(ot)
 	if err != nil {
 		return nil, err
 	}
-	if ot.Kind() == reflect.Ptr {
-		schm.Options = append(schm.Options, &pipepb.Option{
-			Name: optGoNillable,
-		})
+	if ftype != nil {
+		schm := ftype.GetRowType().GetSchema()
+		schm = proto.Clone(schm).(*pipepb.Schema)
+		if ot.Kind() == reflect.Ptr {
+			schm.Options = append(schm.Options, &pipepb.Option{
+				Name: optGoNillable,
+			})
+		}
+		if lID != "" {
+			schm.Options = append(schm.Options, logicalOption(lID))
+		}
+		schm.Id = r.getNextID()
+		r.typeToSchema[ot] = schm
+		r.idToType[schm.GetId()] = ot
+		return schm, nil
 	}
-	return schm, nil
+
+	t := reflectx.SkipPtr(ot)
+
+	schm, err := r.structToSchema(t)
+	if err != nil {
+		return nil, err
+	}
+	// Cache the pointer type here with it's own id.
+	pt := reflect.PtrTo(t)
+	schm = proto.Clone(schm).(*pipepb.Schema)
+	schm.Id = r.getNextID()
+	schm.Options = append(schm.Options, &pipepb.Option{
+		Name: optGoNillable,
+	})
+	r.idToType[schm.GetId()] = pt
+	r.typeToSchema[pt] = schm
+
+	// Return whatever the original type was.
+	return r.typeToSchema[ot], nil

Review comment:
       After reading a little further down here, I think I might be missing some implicit assumption here. Is everything after line 360 assuming that if the type wasn't found above in either `typeToSchema` or `logicalTypeToFieldType` then it must be a pointer type? Because we return the original type, but it wouldn't be present in that map unless `ot` and `pt` matched, right?
   
   Edit: Or maybe this works here because we called `structToSchema` on the non-pointer version, and then also added the pointer version, so one or the other is guaranteed to be present? That seems worth adding a comment too. Like:
   ```
   // Both pointer and non-pointer variants of the original type are registered, so we can return whatever the original type was.
   ```




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