fix: SPDX output performance with many relationships (#3053)

internal/relationship/binary/binary_dependencies.go

@@ -21,27 +21,22 @@ func NewDependencyRelationships(resolver file.Resolver, accessor sbomsync.Access
 
 	// 3. craft package-to-package relationships for each binary that represent shared library dependencies
 	//note: we only care about package-to-package relationships
-	var relIndex *relationship.Index
-	accessor.ReadFromSBOM(func(s *sbom.SBOM) {
-		relIndex = relationship.NewIndex(s.Relationships...)
-	})
-
-	return generateRelationships(resolver, accessor, index, relIndex)
+	return generateRelationships(resolver, accessor, index)
 }
 
-func generateRelationships(resolver file.Resolver, accessor sbomsync.Accessor, index *sharedLibraryIndex, relIndex *relationship.Index) []artifact.Relationship {
-	// read all existing dependencyOf relationships
-	accessor.ReadFromSBOM(func(s *sbom.SBOM) {
-		for _, r := range s.Relationships {
-			if r.Type != artifact.DependencyOfRelationship {
-				continue
-			}
-			relIndex.Track(r)
-		}
-	})
+func generateRelationships(resolver file.Resolver, accessor sbomsync.Accessor, index *sharedLibraryIndex) []artifact.Relationship {
+	newRelationships := relationship.NewIndex()
 
 	// find all package-to-package relationships for shared library dependencies
 	accessor.ReadFromSBOM(func(s *sbom.SBOM) {
+		relIndex := relationship.NewIndex(s.Relationships...)
+
+		addRelationship := func(r artifact.Relationship) {
+			if !relIndex.Contains(r) {
+				newRelationships.Add(r)
+			}
+		}
+
 		for _, parentPkg := range s.Artifacts.Packages.Sorted(pkg.BinaryPkg) {
 			for _, evidentLocation := range parentPkg.Locations.ToSlice() {
 				if evidentLocation.Annotations[pkg.EvidenceAnnotationKey] != pkg.PrimaryEvidenceAnnotation {
@@ -54,12 +49,12 @@ func generateRelationships(resolver file.Resolver, accessor sbomsync.Accessor, i
 					continue
 				}
 
-				populateRelationships(exec, parentPkg, resolver, relIndex, index)
+				populateRelationships(exec, parentPkg, resolver, addRelationship, index)
 			}
 		}
 	})
 
-	return relIndex.NewRelationships()
+	return newRelationships.All()
 }
 
 // PackagesToRemove returns a list of binary packages (resolved by the ELF cataloger) that should be removed from the SBOM
@@ -147,7 +142,7 @@ func getBinaryPackagesToDelete(resolver file.Resolver, s *sbom.SBOM) []artifact.
 	return pkgsToDelete
 }
 
-func populateRelationships(exec file.Executable, parentPkg pkg.Package, resolver file.Resolver, relIndex *relationship.Index, index *sharedLibraryIndex) {
+func populateRelationships(exec file.Executable, parentPkg pkg.Package, resolver file.Resolver, addRelationship func(artifact.Relationship), index *sharedLibraryIndex) {
 	for _, libReference := range exec.ImportedLibraries {
 		// for each library reference, check s.Artifacts.Packages.Sorted(pkg.BinaryPkg) for a binary package that represents that library
 		// if found, create a relationship between the parent package and the library package
@@ -167,7 +162,7 @@ func populateRelationships(exec file.Executable, parentPkg pkg.Package, resolver
 			realBaseName := path.Base(loc.RealPath)
 			pkgCollection := index.owningLibraryPackage(realBaseName)
 			if pkgCollection.PackageCount() < 1 {
-				relIndex.Add(
+				addRelationship(
 					artifact.Relationship{
 						From: loc.Coordinates,
 						To:   parentPkg,
@@ -176,7 +171,7 @@ func populateRelationships(exec file.Executable, parentPkg pkg.Package, resolver
 				)
 			}
 			for _, p := range pkgCollection.Sorted() {
-				relIndex.Add(
+				addRelationship(
 					artifact.Relationship{
 						From: p,
 						To:   parentPkg,

internal/relationship/binary/binary_dependencies_test.go

@@ -2,6 +2,7 @@ package binary
 
 import (
 	"path"
+	"strings"
 	"testing"
 
 	"github.com/google/go-cmp/cmp"
@@ -328,7 +329,20 @@ func relationshipComparer(x, y []artifact.Relationship) string {
 		artifact.Relationship{},
 		file.LocationSet{},
 		pkg.LicenseSet{},
-	))
+	), cmpopts.SortSlices(lessRelationships))
+}
+
+func lessRelationships(r1, r2 artifact.Relationship) bool {
+	c := strings.Compare(string(r1.Type), string(r2.Type))
+	if c != 0 {
+		return c < 0
+	}
+	c = strings.Compare(string(r1.From.ID()), string(r2.From.ID()))
+	if c != 0 {
+		return c < 0
+	}
+	c = strings.Compare(string(r1.To.ID()), string(r2.To.ID()))
+	return c < 0
 }
 
 func newAccessor(pkgs []pkg.Package, coordinateIndex map[file.Coordinates]file.Executable, preexistingRelationships []artifact.Relationship) sbomsync.Accessor {

internal/relationship/index.go

@@ -1,88 +1,181 @@
 package relationship
 
 import (
-	"github.com/scylladb/go-set/strset"
+	"slices"
+	"strings"
 
 	"github.com/anchore/syft/syft/artifact"
+	"github.com/anchore/syft/syft/file"
 )
 
+// Index indexes relationships, preventing duplicates
 type Index struct {
-	typesByFromTo map[artifact.ID]map[artifact.ID]*strset.Set
-	existing      []artifact.Relationship
-	additional    []artifact.Relationship
+	all    []*sortableRelationship
+	fromID map[artifact.ID]*mappedRelationships
+	toID   map[artifact.ID]*mappedRelationships
 }
 
-func NewIndex(existing ...artifact.Relationship) *Index {
-	r := &Index{
-		typesByFromTo: make(map[artifact.ID]map[artifact.ID]*strset.Set),
-	}
-	r.TrackAll(existing...)
-	return r
+// NewIndex returns a new relationship Index
+func NewIndex(relationships ...artifact.Relationship) *Index {
+	out := Index{}
+	out.Add(relationships...)
+	return &out
 }
 
-func (i *Index) track(r artifact.Relationship) bool {
-	fromID := r.From.ID()
-	if _, ok := i.typesByFromTo[fromID]; !ok {
-		i.typesByFromTo[fromID] = make(map[artifact.ID]*strset.Set)
+// Add adds all the given relationships to the index, without adding duplicates
+func (i *Index) Add(relationships ...artifact.Relationship) {
+	if i.fromID == nil {
+		i.fromID = map[artifact.ID]*mappedRelationships{}
+	}
+	if i.toID == nil {
+		i.toID = map[artifact.ID]*mappedRelationships{}
 	}
 
-	toID := r.To.ID()
-	if _, ok := i.typesByFromTo[fromID][toID]; !ok {
-		i.typesByFromTo[fromID][toID] = strset.New()
+	// store appropriate indexes for stable ordering to minimize ID() calls
+	for _, r := range relationships {
+		// prevent duplicates
+		if i.Contains(r) {
+			continue
+		}
+
+		fromID := r.From.ID()
+		toID := r.To.ID()
+
+		relationship := &sortableRelationship{
+			from:         fromID,
+			to:           toID,
+			relationship: r,
+		}
+
+		// add to all relationships
+		i.all = append(i.all, relationship)
+
+		// add from -> to mapping
+		mapped := i.fromID[fromID]
+		if mapped == nil {
+			mapped = &mappedRelationships{}
+			i.fromID[fromID] = mapped
+		}
+		mapped.add(toID, relationship)
+
+		// add to -> from mapping
+		mapped = i.toID[toID]
+		if mapped == nil {
+			mapped = &mappedRelationships{}
+			i.toID[toID] = mapped
+		}
+		mapped.add(fromID, relationship)
 	}
-
-	var exists bool
-	if i.typesByFromTo[fromID][toID].Has(string(r.Type)) {
-		exists = true
-	}
-
-	i.typesByFromTo[fromID][toID].Add(string(r.Type))
-
-	return !exists
 }
 
-// Track this relationship as "exists" in the index (this is used to prevent duplicate relationships from being added).
-// returns true if the relationship is new to the index, false otherwise.
-func (i *Index) Track(r artifact.Relationship) bool {
-	unique := i.track(r)
-	if unique {
-		i.existing = append(i.existing, r)
-	}
-	return unique
+// From returns all relationships from the given identifiable, with specified types
+func (i *Index) From(identifiable artifact.Identifiable, types ...artifact.RelationshipType) []artifact.Relationship {
+	return toSortedSlice(fromMapped(i.fromID, identifiable), types)
 }
 
-// Add a new relationship to the index, returning true if the relationship is new to the index, false otherwise (thus is a duplicate).
-func (i *Index) Add(r artifact.Relationship) bool {
-	if i.track(r) {
-		i.additional = append(i.additional, r)
-		return true
+// To returns all relationships to the given identifiable, with specified types
+func (i *Index) To(identifiable artifact.Identifiable, types ...artifact.RelationshipType) []artifact.Relationship {
+	return toSortedSlice(fromMapped(i.toID, identifiable), types)
+}
+
+// References returns all relationships that reference to or from the given identifiable
+func (i *Index) References(identifiable artifact.Identifiable, types ...artifact.RelationshipType) []artifact.Relationship {
+	return toSortedSlice(append(fromMapped(i.fromID, identifiable), fromMapped(i.toID, identifiable)...), types)
+}
+
+// Coordinates returns all coordinates for the provided identifiable for provided relationship types
+// If no types are provided, all relationship types are considered.
+func (i *Index) Coordinates(identifiable artifact.Identifiable, types ...artifact.RelationshipType) []file.Coordinates {
+	var coordinates []file.Coordinates
+	for _, relationship := range i.References(identifiable, types...) {
+		cords := extractCoordinates(relationship)
+		coordinates = append(coordinates, cords...)
+	}
+	return coordinates
+}
+
+// Contains indicates the relationship is present in this index
+func (i *Index) Contains(r artifact.Relationship) bool {
+	if mapped := i.fromID[r.From.ID()]; mapped != nil {
+		if ids := mapped.typeMap[r.Type]; ids != nil {
+			return ids[r.To.ID()] != nil
+		}
 	}
 	return false
 }
 
-func (i *Index) TrackAll(rs ...artifact.Relationship) {
-	for _, r := range rs {
-		i.Track(r)
+// All returns a sorted set of relationships matching all types, or all relationships if no types specified
+func (i *Index) All(types ...artifact.RelationshipType) []artifact.Relationship {
+	return toSortedSlice(i.all, types)
+}
+
+func fromMapped(idMap map[artifact.ID]*mappedRelationships, identifiable artifact.Identifiable) []*sortableRelationship {
+	if identifiable == nil || idMap == nil {
+		return nil
 	}
-}
-
-func (i *Index) AddAll(rs ...artifact.Relationship) {
-	for _, r := range rs {
-		i.Add(r)
+	mapped := idMap[identifiable.ID()]
+	if mapped == nil {
+		return nil
 	}
+	return mapped.allRelated
 }
 
-func (i *Index) NewRelationships() []artifact.Relationship {
-	return i.additional
+func toSortedSlice(relationships []*sortableRelationship, types []artifact.RelationshipType) []artifact.Relationship {
+	// always return sorted for SBOM stability
+	slices.SortFunc(relationships, sortFunc)
+	var out []artifact.Relationship
+	for _, r := range relationships {
+		if len(types) == 0 || slices.Contains(types, r.relationship.Type) {
+			out = append(out, r.relationship)
+		}
+	}
+	return out
 }
 
-func (i *Index) ExistingRelationships() []artifact.Relationship {
-	return i.existing
+func extractCoordinates(relationship artifact.Relationship) (results []file.Coordinates) {
+	if coordinates, exists := relationship.From.(file.Coordinates); exists {
+		results = append(results, coordinates)
+	}
+
+	if coordinates, exists := relationship.To.(file.Coordinates); exists {
+		results = append(results, coordinates)
+	}
+
+	return results
 }
 
-func (i *Index) AllUniqueRelationships() []artifact.Relationship {
-	var all []artifact.Relationship
-	all = append(all, i.existing...)
-	all = append(all, i.additional...)
-	return all
+type mappedRelationships struct {
+	typeMap    map[artifact.RelationshipType]map[artifact.ID]*sortableRelationship
+	allRelated []*sortableRelationship
+}
+
+func (m *mappedRelationships) add(id artifact.ID, newRelationship *sortableRelationship) {
+	m.allRelated = append(m.allRelated, newRelationship)
+	if m.typeMap == nil {
+		m.typeMap = map[artifact.RelationshipType]map[artifact.ID]*sortableRelationship{}
+	}
+	typeMap := m.typeMap[newRelationship.relationship.Type]
+	if typeMap == nil {
+		typeMap = map[artifact.ID]*sortableRelationship{}
+		m.typeMap[newRelationship.relationship.Type] = typeMap
+	}
+	typeMap[id] = newRelationship
+}
+
+type sortableRelationship struct {
+	from         artifact.ID
+	to           artifact.ID
+	relationship artifact.Relationship
+}
+
+func sortFunc(a, b *sortableRelationship) int {
+	cmp := strings.Compare(string(a.relationship.Type), string(b.relationship.Type))
+	if cmp != 0 {
+		return cmp
+	}
+	cmp = strings.Compare(string(a.from), string(b.from))
+	if cmp != 0 {
+		return cmp
+	}
+	return strings.Compare(string(a.to), string(b.to))
 }

internal/relationship/index_test.go

@@ -3,223 +3,231 @@ package relationship
 import (
 	"testing"
 
-	"github.com/google/go-cmp/cmp"
+	"github.com/stretchr/testify/require"
 
 	"github.com/anchore/syft/syft/artifact"
+	"github.com/anchore/syft/syft/file"
+	"github.com/anchore/syft/syft/pkg"
 )
 
-func Test_newRelationshipIndex(t *testing.T) {
-	from := fakeIdentifiable{id: "from"}
-	to := fakeIdentifiable{id: "to"}
-	tests := []struct {
-		name           string
-		given          []artifact.Relationship
-		track          []artifact.Relationship
-		add            []artifact.Relationship
-		wantExisting   []string
-		wantAdditional []string
-	}{
-		{
-			name: "empty",
-		},
-		{
-			name: "tracks existing relationships",
-			given: []artifact.Relationship{
-				{
-					From: from,
-					To:   to,
-					Type: artifact.EvidentByRelationship,
-				},
-			},
-			wantExisting: []string{"from [evident-by] to"},
-		},
-		{
-			name: "deduplicate tracked relationships",
-			given: []artifact.Relationship{
-				{
-					From: from,
-					To:   to,
-					Type: artifact.EvidentByRelationship,
-				},
-				{
-					From: from,
-					To:   to,
-					Type: artifact.EvidentByRelationship,
-				},
-				{
-					From: from,
-					To:   to,
-					Type: artifact.EvidentByRelationship,
-				},
-			},
-			track: []artifact.Relationship{
-				{
-					From: from,
-					To:   to,
-					Type: artifact.EvidentByRelationship,
-				},
-				{
-					From: from,
-					To:   to,
-					Type: artifact.EvidentByRelationship,
-				},
-			},
-			wantExisting: []string{"from [evident-by] to"},
-		},
-		{
-			name: "deduplicate any input relationships",
-			given: []artifact.Relationship{
-				{
-					From: from,
-					To:   to,
-					Type: artifact.EvidentByRelationship,
-				},
-				{
-					From: from,
-					To:   to,
-					Type: artifact.EvidentByRelationship,
-				},
-			},
-			track: []artifact.Relationship{
-				{
-					From: from,
-					To:   to,
-					Type: artifact.EvidentByRelationship,
-				},
-				{
-					From: from,
-					To:   to,
-					Type: artifact.EvidentByRelationship,
-				},
-			},
-			add: []artifact.Relationship{
-				{
-					From: from,
-					To:   to,
-					Type: artifact.EvidentByRelationship,
-				},
-				{
-					From: from,
-					To:   to,
-					Type: artifact.EvidentByRelationship,
-				},
-			},
-			wantExisting: []string{"from [evident-by] to"},
-		},
-		{
-			name: "deduplicate any added relationships",
-			add: []artifact.Relationship{
-				{
-					From: from,
-					To:   to,
-					Type: artifact.EvidentByRelationship,
-				},
-				{
-					From: from,
-					To:   to,
-					Type: artifact.EvidentByRelationship,
-				},
-			},
-			wantAdditional: []string{"from [evident-by] to"},
-		},
+func Test_Index(t *testing.T) {
+	p1 := pkg.Package{
+		Name: "pkg-1",
 	}
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			idx := NewIndex(tt.given...)
-			idx.TrackAll(tt.track...)
-			idx.AddAll(tt.add...)
-			diffRelationships(t, tt.wantExisting, idx.existing)
-			diffRelationships(t, tt.wantAdditional, idx.additional)
-		})
+	p2 := pkg.Package{
+		Name: "pkg-2",
 	}
+	p3 := pkg.Package{
+		Name: "pkg-3",
+	}
+	c1 := file.Coordinates{
+		RealPath: "/coords/1",
+	}
+	c2 := file.Coordinates{
+		RealPath: "/coords/2",
+	}
+
+	for _, p := range []*pkg.Package{&p1, &p2, &p3} {
+		p.SetID()
+	}
+
+	r1 := artifact.Relationship{
+		From: p1,
+		To:   p2,
+		Type: artifact.DependencyOfRelationship,
+	}
+	r2 := artifact.Relationship{
+		From: p1,
+		To:   p3,
+		Type: artifact.DependencyOfRelationship,
+	}
+	r3 := artifact.Relationship{
+		From: p1,
+		To:   c1,
+		Type: artifact.ContainsRelationship,
+	}
+	r4 := artifact.Relationship{
+		From: p2,
+		To:   c2,
+		Type: artifact.ContainsRelationship,
+	}
+	r5 := artifact.Relationship{
+		From: p3,
+		To:   c2,
+		Type: artifact.ContainsRelationship,
+	}
+
+	dup := artifact.Relationship{
+		From: p3,
+		To:   c2,
+		Type: artifact.ContainsRelationship,
+	}
+
+	idx := NewIndex(r1, r2, r3, r4, r5, dup)
+	require.ElementsMatch(t, slice(r1, r2, r3, r4, r5), idx.All())
+
+	require.ElementsMatch(t, slice(r1, r4), idx.References(p2))
+	require.ElementsMatch(t, slice(r4), idx.References(p2, artifact.ContainsRelationship))
+
+	require.ElementsMatch(t, slice(r1), idx.To(p2))
+	require.ElementsMatch(t, []artifact.Relationship(nil), idx.To(p2, artifact.ContainsRelationship))
+
+	require.ElementsMatch(t, slice(r4), idx.From(p2))
+	require.ElementsMatch(t, slice(r4), idx.From(p2, artifact.ContainsRelationship))
 }
 
-func diffRelationships(t *testing.T, expected []string, actual []artifact.Relationship) {
-	if d := cmp.Diff(expected, stringRelationships(actual)); d != "" {
-		t.Errorf("unexpected relationships (-want, +got): %s", d)
+func Test_sortOrder(t *testing.T) {
+	r1 := artifact.Relationship{
+		From: id("1"),
+		To:   id("2"),
+		Type: "1",
 	}
-}
-
-func stringRelationships(relationships []artifact.Relationship) []string {
-	var result []string
-	for _, r := range relationships {
-		result = append(result, string(r.From.ID())+" ["+string(r.Type)+"] "+string(r.To.ID()))
+	r2 := artifact.Relationship{
+		From: id("2"),
+		To:   id("3"),
+		Type: "1",
 	}
-	return result
-
-}
-
-func Test_relationshipIndex_track(t *testing.T) {
-	from := fakeIdentifiable{id: "from"}
-	to := fakeIdentifiable{id: "to"}
-	relationship := artifact.Relationship{From: from, To: to, Type: artifact.EvidentByRelationship}
-	tests := []struct {
-		name     string
-		existing []artifact.Relationship
-		given    artifact.Relationship
-		want     bool
-	}{
-		{
-			name:     "track returns true for a new relationship",
-			existing: []artifact.Relationship{},
-			given:    relationship,
-			want:     true,
-		},
-		{
-			name:     "track returns false for an existing relationship",
-			existing: []artifact.Relationship{relationship},
-			given:    relationship,
-			want:     false,
-		},
+	r3 := artifact.Relationship{
+		From: id("3"),
+		To:   id("4"),
+		Type: "1",
 	}
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			i := NewIndex(tt.existing...)
-			if got := i.Track(tt.given); got != tt.want {
-				t.Errorf("track() = %v, want %v", got, tt.want)
-			}
-		})
+	r4 := artifact.Relationship{
+		From: id("1"),
+		To:   id("2"),
+		Type: "2",
 	}
-}
-
-func Test_relationshipIndex_add(t *testing.T) {
-	from := fakeIdentifiable{id: "from"}
-	to := fakeIdentifiable{id: "to"}
-	relationship := artifact.Relationship{From: from, To: to, Type: artifact.EvidentByRelationship}
-	tests := []struct {
-		name     string
-		existing []artifact.Relationship
-		given    artifact.Relationship
-		want     bool
-	}{
-		{
-			name:     "add returns true for a new relationship",
-			existing: []artifact.Relationship{},
-			given:    relationship,
-			want:     true,
-		},
-		{
-			name:     "add returns false for an existing relationship",
-			existing: []artifact.Relationship{relationship},
-			given:    relationship,
-			want:     false,
-		},
+	r5 := artifact.Relationship{
+		From: id("2"),
+		To:   id("3"),
+		Type: "2",
 	}
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			i := NewIndex(tt.existing...)
-			if got := i.Add(tt.given); got != tt.want {
-				t.Errorf("add() = %v, want %v", got, tt.want)
-			}
-		})
+	dup := artifact.Relationship{
+		From: id("2"),
+		To:   id("3"),
+		Type: "2",
+	}
+	r6 := artifact.Relationship{
+		From: id("2"),
+		To:   id("3"),
+		Type: "3",
 	}
 
+	idx := NewIndex(r5, r2, r6, r4, r1, r3, dup)
+	require.EqualValues(t, slice(r1, r2, r3, r4, r5, r6), idx.All())
+
+	require.EqualValues(t, slice(r1, r4), idx.From(id("1")))
+
+	require.EqualValues(t, slice(r2, r5, r6), idx.To(id("3")))
+
+	rLast := artifact.Relationship{
+		From: id("0"),
+		To:   id("3"),
+		Type: "9999",
+	}
+
+	rFirst := artifact.Relationship{
+		From: id("0"),
+		To:   id("3"),
+		Type: "1",
+	}
+
+	rMid := artifact.Relationship{
+		From: id("0"),
+		To:   id("1"),
+		Type: "2",
+	}
+
+	idx.Add(rLast, rFirst, rMid)
+
+	require.EqualValues(t, slice(rFirst, r1, r2, r3, rMid, r4, r5, r6, rLast), idx.All())
+
+	require.EqualValues(t, slice(rFirst, r2, r5, r6, rLast), idx.To(id("3")))
 }
 
-type fakeIdentifiable struct {
-	id string
+func Test_Coordinates(t *testing.T) {
+	p1 := pkg.Package{
+		Name: "pkg-1",
+	}
+	p2 := pkg.Package{
+		Name: "pkg-2",
+	}
+	p3 := pkg.Package{
+		Name: "pkg-3",
+	}
+	c1 := file.Coordinates{
+		RealPath: "/coords/1",
+	}
+	c2 := file.Coordinates{
+		RealPath: "/coords/2",
+	}
+	c3 := file.Coordinates{
+		RealPath: "/coords/3",
+	}
+	c4 := file.Coordinates{
+		RealPath: "/coords/4",
+	}
+
+	for _, p := range []*pkg.Package{&p1, &p2, &p3} {
+		p.SetID()
+	}
+
+	r1 := artifact.Relationship{
+		From: p1,
+		To:   p2,
+		Type: artifact.DependencyOfRelationship,
+	}
+	r2 := artifact.Relationship{
+		From: p1,
+		To:   p3,
+		Type: artifact.DependencyOfRelationship,
+	}
+	r3 := artifact.Relationship{
+		From: p1,
+		To:   c1,
+		Type: artifact.ContainsRelationship,
+	}
+	r4 := artifact.Relationship{
+		From: p2,
+		To:   c2,
+		Type: artifact.ContainsRelationship,
+	}
+	r5 := artifact.Relationship{
+		From: p3,
+		To:   c1,
+		Type: artifact.ContainsRelationship,
+	}
+	r6 := artifact.Relationship{
+		From: p3,
+		To:   c2,
+		Type: artifact.ContainsRelationship,
+	}
+	r7 := artifact.Relationship{
+		From: c1,
+		To:   c3,
+		Type: artifact.ContainsRelationship,
+	}
+	r8 := artifact.Relationship{
+		From: c3,
+		To:   c4,
+		Type: artifact.ContainsRelationship,
+	}
+
+	idx := NewIndex(r1, r2, r3, r4, r5, r6, r7, r8)
+
+	got := idx.Coordinates(p1)
+	require.ElementsMatch(t, slice(c1), got)
+
+	got = idx.Coordinates(p3)
+	require.ElementsMatch(t, slice(c1, c2), got)
 }
 
-func (f fakeIdentifiable) ID() artifact.ID {
-	return artifact.ID(f.id)
+type id string
+
+func (i id) ID() artifact.ID {
+	return artifact.ID(i)
+}
+
+func slice[T any](values ...T) []T {
+	return values
 }