consolidate aggregation of parent-item exclude map (#3258)

introduces a new type wrapping a nested map so that aggregation of globally excluded items in driveish services don't need to manage the map updates themselves.

---

#### Does this PR need a docs update or release note?

- [x] ⛔ No

#### Type of change

- [x] 🧹 Tech Debt/Cleanup

#### Issue(s)

* #2340

#### Test Plan

- [x] ⚡ Unit test
- [x] 💚 E2E

src/internal/common/prefixmatcher/mock/mock.go

@@ -0,0 +1,44 @@
+package mock
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/alcionai/corso/src/internal/common/prefixmatcher"
+)
+
+var _ prefixmatcher.StringSetReader = &PrefixMap{}
+
+type PrefixMap struct {
+	prefixmatcher.StringSetBuilder
+}
+
+func NewPrefixMap(m map[string]map[string]struct{}) *PrefixMap {
+	r := PrefixMap{StringSetBuilder: prefixmatcher.NewMatcher[map[string]struct{}]()}
+
+	for k, v := range m {
+		r.Add(k, v)
+	}
+
+	return &r
+}
+
+func (pm PrefixMap) AssertEqual(t *testing.T, r prefixmatcher.StringSetReader) {
+	if pm.Empty() {
+		require.True(t, r.Empty(), "both prefix maps are empty")
+		return
+	}
+
+	pks := pm.Keys()
+	rks := r.Keys()
+
+	assert.ElementsMatch(t, pks, rks, "prefix keys match")
+
+	for _, pk := range pks {
+		p, _ := pm.Get(pk)
+		r, _ := r.Get(pk)
+		assert.Equal(t, p, r, "values match")
+	}
+}

src/internal/common/prefixmatcher/prefix_matcher.go

@@ -2,27 +2,47 @@ package prefixmatcher
 
 import (
 	"strings"
+
+	"golang.org/x/exp/maps"
 )
 
-type View[T any] interface {
+type Reader[T any] interface {
 	Get(key string) (T, bool)
 	LongestPrefix(key string) (string, T, bool)
 	Empty() bool
+	Keys() []string
 }
 
-type Matcher[T any] interface {
+type Builder[T any] interface {
 	// Add adds or updates the item with key to have value value.
 	Add(key string, value T)
-	View[T]
+	Reader[T]
 }
 
+// ---------------------------------------------------------------------------
+// Implementation
+// ---------------------------------------------------------------------------
+
+// prefixMatcher implements Builder
 type prefixMatcher[T any] struct {
 	data map[string]T
 }
 
-func (m *prefixMatcher[T]) Add(key string, value T) {
-	m.data[key] = value
+func NewMatcher[T any]() Builder[T] {
+	return &prefixMatcher[T]{
+		data: map[string]T{},
 	}
+}
+
+func NopReader[T any]() *prefixMatcher[T] {
+	return &prefixMatcher[T]{
+		data: make(map[string]T),
+	}
+}
+
+func (m *prefixMatcher[T]) Add(key string, value T) { m.data[key] = value }
+func (m prefixMatcher[T]) Empty() bool              { return len(m.data) == 0 }
+func (m prefixMatcher[T]) Keys() []string           { return maps.Keys(m.data) }
 
 func (m *prefixMatcher[T]) Get(key string) (T, bool) {
 	if m == nil {
@@ -58,11 +78,3 @@ func (m *prefixMatcher[T]) LongestPrefix(key string) (string, T, bool) {
 
 	return rk, rv, found
 }
-
-func (m prefixMatcher[T]) Empty() bool {
-	return len(m.data) == 0
-}
-
-func NewMatcher[T any]() Matcher[T] {
-	return &prefixMatcher[T]{data: map[string]T{}}
-}

src/internal/common/prefixmatcher/prefix_matcher_test.go

@@ -5,6 +5,7 @@ import (
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/suite"
+	"golang.org/x/exp/maps"
 
 	"github.com/alcionai/corso/src/internal/common/prefixmatcher"
 	"github.com/alcionai/corso/src/internal/tester"
@@ -41,6 +42,8 @@ func (suite *PrefixMatcherUnitSuite) TestAdd_Get() {
 		assert.True(t, ok, "searching for key", k)
 		assert.Equal(t, v, val, "returned value")
 	}
+
+	assert.ElementsMatch(t, maps.Keys(kvs), pm.Keys())
 }
 
 func (suite *PrefixMatcherUnitSuite) TestLongestPrefix() {

src/internal/common/prefixmatcher/string_set_matcher.go

@@ -0,0 +1,122 @@
+package prefixmatcher
+
+import "golang.org/x/exp/maps"
+
+// StringSetReader is a reader designed specifially to contain a set
+// of string values (ie: Reader[map[string]struct{}]).
+// This is a quality-of-life typecast for the generic Reader.
+type StringSetReader interface {
+	Reader[map[string]struct{}]
+}
+
+// StringSetReader is a builder designed specifially to contain a set
+// of string values (ie: Builder[map[string]struct{}]).
+// This is a quality-of-life typecast for the generic Builder.
+type StringSetBuilder interface {
+	Builder[map[string]struct{}]
+}
+
+// ---------------------------------------------------------------------------
+// Implementation
+// ---------------------------------------------------------------------------
+
+var (
+	_ StringSetReader  = &StringSetMatcher{}
+	_ StringSetBuilder = &StringSetMatchBuilder{}
+)
+
+// Items that should be excluded when sourcing data from the base backup.
+// Parent Path -> item ID -> {}
+type StringSetMatcher struct {
+	ssb StringSetBuilder
+}
+
+func (m *StringSetMatcher) LongestPrefix(parent string) (string, map[string]struct{}, bool) {
+	if m == nil {
+		return "", nil, false
+	}
+
+	return m.ssb.LongestPrefix(parent)
+}
+
+func (m *StringSetMatcher) Empty() bool {
+	return m == nil || m.ssb.Empty()
+}
+
+func (m *StringSetMatcher) Get(parent string) (map[string]struct{}, bool) {
+	if m == nil {
+		return nil, false
+	}
+
+	return m.ssb.Get(parent)
+}
+
+func (m *StringSetMatcher) Keys() []string {
+	if m == nil {
+		return []string{}
+	}
+
+	return m.ssb.Keys()
+}
+
+func (m *StringSetMatchBuilder) ToReader() *StringSetMatcher {
+	if m == nil {
+		return nil
+	}
+
+	return m.ssm
+}
+
+// Items that should be excluded when sourcing data from the base backup.
+// Parent Path -> item ID -> {}
+type StringSetMatchBuilder struct {
+	ssm *StringSetMatcher
+}
+
+func NewStringSetBuilder() *StringSetMatchBuilder {
+	return &StringSetMatchBuilder{
+		ssm: &StringSetMatcher{
+			ssb: NewMatcher[map[string]struct{}](),
+		},
+	}
+}
+
+// copies all items into the key's bucket.
+func (m *StringSetMatchBuilder) Add(key string, items map[string]struct{}) {
+	if m == nil {
+		return
+	}
+
+	vs, ok := m.ssm.Get(key)
+	if !ok {
+		m.ssm.ssb.Add(key, items)
+		return
+	}
+
+	maps.Copy(vs, items)
+	m.ssm.ssb.Add(key, vs)
+}
+
+func (m *StringSetMatchBuilder) LongestPrefix(parent string) (string, map[string]struct{}, bool) {
+	return m.ssm.LongestPrefix(parent)
+}
+
+func (m *StringSetMatchBuilder) Empty() bool {
+	return m == nil || m.ssm.Empty()
+}
+
+func (m *StringSetMatchBuilder) Get(parent string) (map[string]struct{}, bool) {
+	if m == nil {
+		return nil, false
+	}
+
+	return m.ssm.Get(parent)
+}
+
+func (m *StringSetMatchBuilder) Keys() []string {
+	if m == nil {
+		return []string{}
+	}
+
+	return m.ssm.Keys()
+}

src/internal/common/prefixmatcher/string_set_matcher_test.go

@@ -0,0 +1,166 @@
+package prefixmatcher_test
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/suite"
+	"golang.org/x/exp/maps"
+
+	"github.com/alcionai/corso/src/internal/common/prefixmatcher"
+	"github.com/alcionai/corso/src/internal/tester"
+)
+
+type StringSetUnitSuite struct {
+	tester.Suite
+}
+
+func TestSTringSetUnitSuite(t *testing.T) {
+	suite.Run(t, &StringSetUnitSuite{Suite: tester.NewUnitSuite(t)})
+}
+
+func (suite *StringSetUnitSuite) TestEmpty() {
+	pm := prefixmatcher.NewStringSetBuilder()
+	assert.True(suite.T(), pm.Empty())
+}
+
+func (suite *StringSetUnitSuite) TestToReader() {
+	var (
+		pr prefixmatcher.StringSetReader
+		t  = suite.T()
+		pm = prefixmatcher.NewStringSetBuilder()
+	)
+
+	pr = pm.ToReader()
+	_, ok := pr.(prefixmatcher.StringSetBuilder)
+	assert.False(t, ok, "cannot cast to builder")
+}
+
+func (suite *StringSetUnitSuite) TestAdd_Get() {
+	t := suite.T()
+	pm := prefixmatcher.NewStringSetBuilder()
+	kvs := map[string]map[string]struct{}{
+		"hello": {"world": {}},
+		"hola":  {"mundo": {}},
+		"foo":   {"bar": {}},
+	}
+
+	for k, v := range kvs {
+		pm.Add(k, v)
+	}
+
+	for k, v := range kvs {
+		val, ok := pm.Get(k)
+		assert.True(t, ok, "searching for key", k)
+		assert.Equal(t, v, val, "returned value")
+	}
+
+	assert.ElementsMatch(t, maps.Keys(kvs), pm.Keys())
+}
+
+func (suite *StringSetUnitSuite) TestAdd_Union() {
+	t := suite.T()
+	pm := prefixmatcher.NewStringSetBuilder()
+	pm.Add("hello", map[string]struct{}{
+		"world": {},
+		"mundo": {},
+	})
+	pm.Add("hello", map[string]struct{}{
+		"goodbye": {},
+		"aideu":   {},
+	})
+
+	expect := map[string]struct{}{
+		"world":   {},
+		"mundo":   {},
+		"goodbye": {},
+		"aideu":   {},
+	}
+
+	result, _ := pm.Get("hello")
+	assert.Equal(t, expect, result)
+	assert.ElementsMatch(t, []string{"hello"}, pm.Keys())
+}
+
+func (suite *StringSetUnitSuite) TestLongestPrefix() {
+	key := "hello"
+	value := "world"
+
+	table := []struct {
+		name          string
+		inputKVs      map[string]map[string]struct{}
+		searchKey     string
+		expectedKey   string
+		expectedValue map[string]struct{}
+		expectedFound assert.BoolAssertionFunc
+	}{
+		{
+			name: "Empty Prefix",
+			inputKVs: map[string]map[string]struct{}{
+				"": {value: {}},
+			},
+			searchKey:     key,
+			expectedKey:   "",
+			expectedValue: map[string]struct{}{value: {}},
+			expectedFound: assert.True,
+		},
+		{
+			name: "Exact Match",
+			inputKVs: map[string]map[string]struct{}{
+				key: {value: {}},
+			},
+			searchKey:     key,
+			expectedKey:   key,
+			expectedValue: map[string]struct{}{value: {}},
+			expectedFound: assert.True,
+		},
+		{
+			name: "Prefix Match",
+			inputKVs: map[string]map[string]struct{}{
+				key[:len(key)-2]: {value: {}},
+			},
+			searchKey:     key,
+			expectedKey:   key[:len(key)-2],
+			expectedValue: map[string]struct{}{value: {}},
+			expectedFound: assert.True,
+		},
+		{
+			name: "Longest Prefix Match",
+			inputKVs: map[string]map[string]struct{}{
+				key[:len(key)-2]: {value: {}},
+				"":               {value + "2": {}},
+				key[:len(key)-4]: {value + "3": {}},
+			},
+			searchKey:     key,
+			expectedKey:   key[:len(key)-2],
+			expectedValue: map[string]struct{}{value: {}},
+			expectedFound: assert.True,
+		},
+		{
+			name: "No Match",
+			inputKVs: map[string]map[string]struct{}{
+				"foo": {value: {}},
+			},
+			searchKey:     key,
+			expectedKey:   "",
+			expectedValue: nil,
+			expectedFound: assert.False,
+		},
+	}
+
+	for _, test := range table {
+		suite.Run(test.name, func() {
+			t := suite.T()
+			pm := prefixmatcher.NewStringSetBuilder()
+
+			for k, v := range test.inputKVs {
+				pm.Add(k, v)
+			}
+
+			k, v, ok := pm.LongestPrefix(test.searchKey)
+			assert.Equal(t, test.expectedKey, k, "key")
+			assert.Equal(t, test.expectedValue, v, "value")
+			test.expectedFound(t, ok, "found")
+		})
+	}
+}

src/internal/connector/data_collections.go

@@ -7,6 +7,7 @@ import (
 	"github.com/alcionai/clues"
 
 	"github.com/alcionai/corso/src/internal/common/idname"
+	"github.com/alcionai/corso/src/internal/common/prefixmatcher"
 	"github.com/alcionai/corso/src/internal/connector/discovery"
 	"github.com/alcionai/corso/src/internal/connector/exchange"
 	"github.com/alcionai/corso/src/internal/connector/graph"
@@ -41,7 +42,7 @@ func (gc *GraphConnector) ProduceBackupCollections(
 	lastBackupVersion int,
 	ctrlOpts control.Options,
 	errs *fault.Bus,
-) ([]data.BackupCollection, map[string]map[string]struct{}, error) {
+) ([]data.BackupCollection, prefixmatcher.StringSetReader, error) {
 	ctx, end := diagnostics.Span(
 		ctx,
 		"gc:produceBackupCollections",
@@ -72,12 +73,12 @@ func (gc *GraphConnector) ProduceBackupCollections(
 
 	var (
 		colls []data.BackupCollection
-		excludes map[string]map[string]struct{}
+		ssmb  *prefixmatcher.StringSetMatcher
 	)
 
 	switch sels.Service {
 	case selectors.ServiceExchange:
-		colls, excludes, err = exchange.DataCollections(
+		colls, ssmb, err = exchange.DataCollections(
 			ctx,
 			sels,
 			owner,
@@ -91,7 +92,7 @@ func (gc *GraphConnector) ProduceBackupCollections(
 		}
 
 	case selectors.ServiceOneDrive:
-		colls, excludes, err = onedrive.DataCollections(
+		colls, ssmb, err = onedrive.DataCollections(
 			ctx,
 			sels,
 			owner,
@@ -108,7 +109,7 @@ func (gc *GraphConnector) ProduceBackupCollections(
 		}
 
 	case selectors.ServiceSharePoint:
-		colls, excludes, err = sharepoint.DataCollections(
+		colls, ssmb, err = sharepoint.DataCollections(
 			ctx,
 			gc.itemClient,
 			sels,
@@ -139,7 +140,7 @@ func (gc *GraphConnector) ProduceBackupCollections(
 		}
 	}
 
-	return colls, excludes, nil
+	return colls, ssmb, nil
 }
 
 func verifyBackupInputs(sels selectors.Selector, siteIDs []string) error {

src/internal/connector/data_collections_test.go

@@ -110,7 +110,7 @@ func (suite *DataCollectionIntgSuite) TestExchangeDataCollection() {
 				control.Defaults(),
 				fault.New(true))
 			require.NoError(t, err, clues.ToCore(err))
-			assert.Empty(t, excludes)
+			assert.True(t, excludes.Empty())
 
 			for range collections {
 				connector.incrementAwaitingMessages()
@@ -215,7 +215,7 @@ func (suite *DataCollectionIntgSuite) TestDataCollections_invalidResourceOwner()
 				fault.New(true))
 			assert.Error(t, err, clues.ToCore(err))
 			assert.Empty(t, collections)
-			assert.Empty(t, excludes)
+			assert.Nil(t, excludes)
 		})
 	}
 }
@@ -272,7 +272,7 @@ func (suite *DataCollectionIntgSuite) TestSharePointDataCollection() {
 				fault.New(true))
 			require.NoError(t, err, clues.ToCore(err))
 			// Not expecting excludes as this isn't an incremental backup.
-			assert.Empty(t, excludes)
+			assert.True(t, excludes.Empty())
 
 			for range collections {
 				connector.incrementAwaitingMessages()
@@ -356,7 +356,7 @@ func (suite *SPCollectionIntgSuite) TestCreateSharePointCollection_Libraries() {
 	require.NoError(t, err, clues.ToCore(err))
 	require.Len(t, cols, 2) // 1 collection, 1 path prefix directory to ensure the root path exists.
 	// No excludes yet as this isn't an incremental backup.
-	assert.Empty(t, excludes)
+	assert.True(t, excludes.Empty())
 
 	t.Logf("cols[0] Path: %s\n", cols[0].FullPath().String())
 	assert.Equal(
@@ -401,7 +401,7 @@ func (suite *SPCollectionIntgSuite) TestCreateSharePointCollection_Lists() {
 	require.NoError(t, err, clues.ToCore(err))
 	assert.Less(t, 0, len(cols))
 	// No excludes yet as this isn't an incremental backup.
-	assert.Empty(t, excludes)
+	assert.True(t, excludes.Empty())
 
 	for _, collection := range cols {
 		t.Logf("Path: %s\n", collection.FullPath().String())

src/internal/connector/exchange/data_collections.go

@@ -7,6 +7,7 @@ import (
 	"github.com/alcionai/clues"
 
 	"github.com/alcionai/corso/src/internal/common/idname"
+	"github.com/alcionai/corso/src/internal/common/prefixmatcher"
 	"github.com/alcionai/corso/src/internal/connector/exchange/api"
 	"github.com/alcionai/corso/src/internal/connector/graph"
 	"github.com/alcionai/corso/src/internal/connector/support"
@@ -170,7 +171,7 @@ func DataCollections(
 	su support.StatusUpdater,
 	ctrlOpts control.Options,
 	errs *fault.Bus,
-) ([]data.BackupCollection, map[string]map[string]struct{}, error) {
+) ([]data.BackupCollection, *prefixmatcher.StringSetMatcher, error) {
 	eb, err := selector.ToExchangeBackup()
 	if err != nil {
 		return nil, nil, clues.Wrap(err, "exchange dataCollection selector").WithClues(ctx)

src/internal/connector/graph_connector_test.go

@@ -538,7 +538,7 @@ func runBackupAndCompare(
 		fault.New(true))
 	require.NoError(t, err, clues.ToCore(err))
 	// No excludes yet because this isn't an incremental backup.
-	assert.Empty(t, excludes)
+	assert.True(t, excludes.Empty())
 
 	t.Logf("Backup enumeration complete in %v\n", time.Since(start))
 
@@ -1121,7 +1121,7 @@ func (suite *GraphConnectorIntegrationSuite) TestMultiFolderBackupDifferentNames
 				fault.New(true))
 			require.NoError(t, err, clues.ToCore(err))
 			// No excludes yet because this isn't an incremental backup.
-			assert.Empty(t, excludes)
+			assert.True(t, excludes.Empty())
 
 			t.Log("Backup enumeration complete")
 
@@ -1280,7 +1280,7 @@ func (suite *GraphConnectorIntegrationSuite) TestBackup_CreatesPrefixCollections
 				fault.New(true))
 			require.NoError(t, err)
 			// No excludes yet because this isn't an incremental backup.
-			assert.Empty(t, excludes)
+			assert.True(t, excludes.Empty())
 
 			t.Logf("Backup enumeration complete in %v\n", time.Since(start))
 

src/internal/connector/mock/connector.go

@@ -4,7 +4,9 @@ import (
 	"context"
 
 	"github.com/alcionai/corso/src/internal/common/idname"
+	"github.com/alcionai/corso/src/internal/common/prefixmatcher"
 	"github.com/alcionai/corso/src/internal/data"
+	"github.com/alcionai/corso/src/internal/operations/inject"
 	"github.com/alcionai/corso/src/pkg/account"
 	"github.com/alcionai/corso/src/pkg/backup/details"
 	"github.com/alcionai/corso/src/pkg/control"
@@ -12,9 +14,11 @@ import (
 	"github.com/alcionai/corso/src/pkg/selectors"
 )
 
+var _ inject.BackupProducer = &GraphConnector{}
+
 type GraphConnector struct {
 	Collections []data.BackupCollection
-	Exclude     map[string]map[string]struct{}
+	Exclude     *prefixmatcher.StringSetMatcher
 
 	Deets *details.Details
 
@@ -33,7 +37,7 @@ func (gc GraphConnector) ProduceBackupCollections(
 	_ *fault.Bus,
 ) (
 	[]data.BackupCollection,
-	map[string]map[string]struct{},
+	prefixmatcher.StringSetReader,
 	error,
 ) {
 	return gc.Collections, gc.Exclude, gc.Err

src/internal/connector/onedrive/collections.go

@@ -12,6 +12,7 @@ import (
 	"github.com/pkg/errors"
 	"golang.org/x/exp/maps"
 
+	"github.com/alcionai/corso/src/internal/common/prefixmatcher"
 	"github.com/alcionai/corso/src/internal/common/ptr"
 	"github.com/alcionai/corso/src/internal/connector/graph"
 	"github.com/alcionai/corso/src/internal/connector/onedrive/api"
@@ -271,11 +272,12 @@ func deserializeMap[T any](reader io.ReadCloser, alreadyFound map[string]T) erro
 func (c *Collections) Get(
 	ctx context.Context,
 	prevMetadata []data.RestoreCollection,
+	ssmb *prefixmatcher.StringSetMatchBuilder,
 	errs *fault.Bus,
-) ([]data.BackupCollection, map[string]map[string]struct{}, error) {
+) ([]data.BackupCollection, error) {
 	prevDeltas, oldPathsByDriveID, err := deserializeMetadata(ctx, prevMetadata, errs)
 	if err != nil {
-		return nil, nil, err
+		return nil, err
 	}
 
 	driveComplete, closer := observe.MessageWithCompletion(ctx, observe.Bulletf("files"))
@@ -285,12 +287,12 @@ func (c *Collections) Get(
 	// Enumerate drives for the specified resourceOwner
 	pager, err := c.drivePagerFunc(c.source, c.service, c.resourceOwner, nil)
 	if err != nil {
-		return nil, nil, graph.Stack(ctx, err)
+		return nil, graph.Stack(ctx, err)
 	}
 
 	drives, err := api.GetAllDrives(ctx, pager, true, maxDrivesRetries)
 	if err != nil {
-		return nil, nil, err
+		return nil, err
 	}
 
 	var (
@@ -298,9 +300,6 @@ func (c *Collections) Get(
 		deltaURLs = map[string]string{}
 		// Drive ID -> folder ID -> folder path
 		folderPaths = map[string]map[string]string{}
-		// Items that should be excluded when sourcing data from the base backup.
-		// Parent Path -> item ID -> {}
-		excludedItems = map[string]map[string]struct{}{}
 	)
 
 	for _, d := range drives {
@@ -336,7 +335,7 @@ func (c *Collections) Get(
 			prevDelta,
 			errs)
 		if err != nil {
-			return nil, nil, err
+			return nil, err
 		}
 
 		// Used for logging below.
@@ -376,19 +375,10 @@ func (c *Collections) Get(
 				c.resourceOwner,
 				c.source)
 			if err != nil {
-				return nil, nil,
-					clues.Wrap(err, "making exclude prefix").WithClues(ictx)
+				return nil, clues.Wrap(err, "making exclude prefix").WithClues(ictx)
 			}
 
-			pstr := p.String()
-
-			eidi, ok := excludedItems[pstr]
-			if !ok {
-				eidi = map[string]struct{}{}
-			}
-
-			maps.Copy(eidi, excluded)
-			excludedItems[pstr] = eidi
+			ssmb.Add(p.String(), excluded)
 
 			continue
 		}
@@ -413,7 +403,7 @@ func (c *Collections) Get(
 			prevPath, err := path.FromDataLayerPath(p, false)
 			if err != nil {
 				err = clues.Wrap(err, "invalid previous path").WithClues(ictx).With("deleted_path", p)
-				return nil, map[string]map[string]struct{}{}, err
+				return nil, err
 			}
 
 			col, err := NewCollection(
@@ -428,7 +418,7 @@ func (c *Collections) Get(
 				CollectionScopeUnknown,
 				true)
 			if err != nil {
-				return nil, map[string]map[string]struct{}{}, clues.Wrap(err, "making collection").WithClues(ictx)
+				return nil, clues.Wrap(err, "making collection").WithClues(ictx)
 			}
 
 			c.CollectionMap[driveID][fldID] = col
@@ -468,7 +458,7 @@ func (c *Collections) Get(
 	}
 
 	// TODO(ashmrtn): Track and return the set of items to exclude.
-	return collections, excludedItems, nil
+	return collections, nil
 }
 
 func updateCollectionPaths(

src/internal/connector/onedrive/collections_test.go

@@ -15,6 +15,8 @@ import (
 	"github.com/stretchr/testify/suite"
 	"golang.org/x/exp/maps"
 
+	"github.com/alcionai/corso/src/internal/common/prefixmatcher"
+	pmMock "github.com/alcionai/corso/src/internal/common/prefixmatcher/mock"
 	"github.com/alcionai/corso/src/internal/connector/graph"
 	gapi "github.com/alcionai/corso/src/internal/connector/graph/api"
 	"github.com/alcionai/corso/src/internal/connector/onedrive/api"
@@ -1283,7 +1285,7 @@ func (suite *OneDriveCollectionsUnitSuite) TestGet() {
 		expectedCollections  map[string]map[data.CollectionState][]string
 		expectedDeltaURLs    map[string]string
 		expectedFolderPaths  map[string]map[string]string
-		expectedDelList      map[string]map[string]struct{}
+		expectedDelList      *pmMock.PrefixMap
 		expectedSkippedCount int
 		doNotMergeItems      bool
 	}{
@@ -1314,9 +1316,9 @@ func (suite *OneDriveCollectionsUnitSuite) TestGet() {
 			expectedFolderPaths: map[string]map[string]string{
 				driveID1: {"root": rootFolderPath1},
 			},
-			expectedDelList: map[string]map[string]struct{}{
+			expectedDelList: pmMock.NewPrefixMap(map[string]map[string]struct{}{
 				rootFolderPath1: getDelList("file"),
-			},
+			}),
 		},
 		{
 			name:   "OneDrive_OneItemPage_NoFolders_NoErrors",
@@ -1345,9 +1347,9 @@ func (suite *OneDriveCollectionsUnitSuite) TestGet() {
 			expectedFolderPaths: map[string]map[string]string{
 				driveID1: {"root": rootFolderPath1},
 			},
-			expectedDelList: map[string]map[string]struct{}{
+			expectedDelList: pmMock.NewPrefixMap(map[string]map[string]struct{}{
 				rootFolderPath1: getDelList("file"),
-			},
+			}),
 		},
 		{
 			name:   "OneDrive_OneItemPage_NoErrors",
@@ -1381,9 +1383,9 @@ func (suite *OneDriveCollectionsUnitSuite) TestGet() {
 					"folder": folderPath1,
 				},
 			},
-			expectedDelList: map[string]map[string]struct{}{
+			expectedDelList: pmMock.NewPrefixMap(map[string]map[string]struct{}{
 				rootFolderPath1: getDelList("file"),
-			},
+			}),
 		},
 		{
 			name:   "OneDrive_OneItemPage_NoErrors_FileRenamedMultiple",
@@ -1418,9 +1420,9 @@ func (suite *OneDriveCollectionsUnitSuite) TestGet() {
 					"folder": folderPath1,
 				},
 			},
-			expectedDelList: map[string]map[string]struct{}{
+			expectedDelList: pmMock.NewPrefixMap(map[string]map[string]struct{}{
 				rootFolderPath1: getDelList("file"),
-			},
+			}),
 		},
 		{
 			name:   "OneDrive_OneItemPage_NoErrors_FileMovedMultiple",
@@ -1455,9 +1457,9 @@ func (suite *OneDriveCollectionsUnitSuite) TestGet() {
 					"folder": folderPath1,
 				},
 			},
-			expectedDelList: map[string]map[string]struct{}{
+			expectedDelList: pmMock.NewPrefixMap(map[string]map[string]struct{}{
 				rootFolderPath1: getDelList("file"),
-			},
+			}),
 		},
 		{
 			name:   "OneDrive_OneItemPage_EmptyDelta_NoErrors",
@@ -1484,9 +1486,9 @@ func (suite *OneDriveCollectionsUnitSuite) TestGet() {
 			},
 			expectedDeltaURLs:   map[string]string{},
 			expectedFolderPaths: map[string]map[string]string{},
-			expectedDelList: map[string]map[string]struct{}{
+			expectedDelList: pmMock.NewPrefixMap(map[string]map[string]struct{}{
 				rootFolderPath1: getDelList("file"),
-			},
+			}),
 		},
 		{
 			name:   "OneDrive_TwoItemPages_NoErrors",
@@ -1528,9 +1530,9 @@ func (suite *OneDriveCollectionsUnitSuite) TestGet() {
 					"folder": folderPath1,
 				},
 			},
-			expectedDelList: map[string]map[string]struct{}{
+			expectedDelList: pmMock.NewPrefixMap(map[string]map[string]struct{}{
 				rootFolderPath1: getDelList("file", "file2"),
-			},
+			}),
 		},
 		{
 			name: "TwoDrives_OneItemPageEach_NoErrors",
@@ -1585,10 +1587,10 @@ func (suite *OneDriveCollectionsUnitSuite) TestGet() {
 					"folder2": folderPath2,
 				},
 			},
-			expectedDelList: map[string]map[string]struct{}{
+			expectedDelList: pmMock.NewPrefixMap(map[string]map[string]struct{}{
 				rootFolderPath1: getDelList("file"),
 				rootFolderPath2: getDelList("file2"),
-			},
+			}),
 		},
 		{
 			name: "TwoDrives_DuplicateIDs_OneItemPageEach_NoErrors",
@@ -1643,10 +1645,10 @@ func (suite *OneDriveCollectionsUnitSuite) TestGet() {
 					"folder": folderPath2,
 				},
 			},
-			expectedDelList: map[string]map[string]struct{}{
+			expectedDelList: pmMock.NewPrefixMap(map[string]map[string]struct{}{
 				rootFolderPath1: getDelList("file"),
 				rootFolderPath2: getDelList("file2"),
-			},
+			}),
 		},
 		{
 			name:   "OneDrive_OneItemPage_Errors",
@@ -1696,7 +1698,7 @@ func (suite *OneDriveCollectionsUnitSuite) TestGet() {
 					"root": rootFolderPath1,
 				},
 			},
-			expectedDelList: map[string]map[string]struct{}{},
+			expectedDelList: pmMock.NewPrefixMap(map[string]map[string]struct{}{}),
 			doNotMergeItems: true,
 		},
 		{
@@ -1738,7 +1740,7 @@ func (suite *OneDriveCollectionsUnitSuite) TestGet() {
 					"folder": folderPath1,
 				},
 			},
-			expectedDelList: map[string]map[string]struct{}{},
+			expectedDelList: pmMock.NewPrefixMap(map[string]map[string]struct{}{}),
 			doNotMergeItems: true,
 		},
 		{
@@ -1780,9 +1782,9 @@ func (suite *OneDriveCollectionsUnitSuite) TestGet() {
 					"folder": folderPath1,
 				},
 			},
-			expectedDelList: map[string]map[string]struct{}{
+			expectedDelList: pmMock.NewPrefixMap(map[string]map[string]struct{}{
 				rootFolderPath1: getDelList("file", "file2"),
-			},
+			}),
 			doNotMergeItems: false,
 		},
 		{
@@ -1824,7 +1826,7 @@ func (suite *OneDriveCollectionsUnitSuite) TestGet() {
 					"folder2": expectedPath1("/folder2"),
 				},
 			},
-			expectedDelList: map[string]map[string]struct{}{},
+			expectedDelList: pmMock.NewPrefixMap(map[string]map[string]struct{}{}),
 			doNotMergeItems: true,
 		},
 		{
@@ -1870,7 +1872,7 @@ func (suite *OneDriveCollectionsUnitSuite) TestGet() {
 					"folder2": expectedPath1("/folder"),
 				},
 			},
-			expectedDelList: map[string]map[string]struct{}{},
+			expectedDelList: pmMock.NewPrefixMap(map[string]map[string]struct{}{}),
 			doNotMergeItems: true,
 		},
 		{
@@ -1915,9 +1917,9 @@ func (suite *OneDriveCollectionsUnitSuite) TestGet() {
 					"folder": folderPath1,
 				},
 			},
-			expectedDelList: map[string]map[string]struct{}{
+			expectedDelList: pmMock.NewPrefixMap(map[string]map[string]struct{}{
 				rootFolderPath1: getDelList("file", "file2"),
-			},
+			}),
 			expectedSkippedCount: 2,
 		},
 		{
@@ -1970,7 +1972,7 @@ func (suite *OneDriveCollectionsUnitSuite) TestGet() {
 					"folder": folderPath1,
 				},
 			},
-			expectedDelList: map[string]map[string]struct{}{},
+			expectedDelList: pmMock.NewPrefixMap(map[string]map[string]struct{}{}),
 			doNotMergeItems: true,
 		},
 		{
@@ -2009,7 +2011,7 @@ func (suite *OneDriveCollectionsUnitSuite) TestGet() {
 					"root": rootFolderPath1,
 				},
 			},
-			expectedDelList: map[string]map[string]struct{}{},
+			expectedDelList: pmMock.NewPrefixMap(map[string]map[string]struct{}{}),
 			doNotMergeItems: true,
 		},
 		{
@@ -2046,7 +2048,7 @@ func (suite *OneDriveCollectionsUnitSuite) TestGet() {
 					"root": rootFolderPath1,
 				},
 			},
-			expectedDelList: map[string]map[string]struct{}{},
+			expectedDelList: pmMock.NewPrefixMap(map[string]map[string]struct{}{}),
 			doNotMergeItems: true,
 		},
 		{
@@ -2087,9 +2089,9 @@ func (suite *OneDriveCollectionsUnitSuite) TestGet() {
 					"root": rootFolderPath1,
 				},
 			},
-			expectedDelList: map[string]map[string]struct{}{
+			expectedDelList: pmMock.NewPrefixMap(map[string]map[string]struct{}{
 				rootFolderPath1: getDelList("file"),
-			},
+			}),
 		},
 		{
 			name:   "One Drive Item Made And Deleted",
@@ -2130,9 +2132,9 @@ func (suite *OneDriveCollectionsUnitSuite) TestGet() {
 					"folder": folderPath1,
 				},
 			},
-			expectedDelList: map[string]map[string]struct{}{
+			expectedDelList: pmMock.NewPrefixMap(map[string]map[string]struct{}{
 				rootFolderPath1: getDelList("file"),
-			},
+			}),
 		},
 		{
 			name:   "One Drive Random Folder Delete",
@@ -2163,7 +2165,7 @@ func (suite *OneDriveCollectionsUnitSuite) TestGet() {
 					"root": rootFolderPath1,
 				},
 			},
-			expectedDelList: map[string]map[string]struct{}{},
+			expectedDelList: pmMock.NewPrefixMap(map[string]map[string]struct{}{}),
 		},
 		{
 			name:   "One Drive Random Item Delete",
@@ -2194,9 +2196,9 @@ func (suite *OneDriveCollectionsUnitSuite) TestGet() {
 					"root": rootFolderPath1,
 				},
 			},
-			expectedDelList: map[string]map[string]struct{}{
+			expectedDelList: pmMock.NewPrefixMap(map[string]map[string]struct{}{
 				rootFolderPath1: getDelList("file"),
-			},
+			}),
 		},
 	}
 	for _, test := range table {
@@ -2269,7 +2271,9 @@ func (suite *OneDriveCollectionsUnitSuite) TestGet() {
 			prevMetadata := []data.RestoreCollection{data.NotFoundRestoreCollection{Collection: mc}}
 			errs := fault.New(true)
 
-			cols, delList, err := c.Get(ctx, prevMetadata, errs)
+			delList := prefixmatcher.NewStringSetBuilder()
+
+			cols, err := c.Get(ctx, prevMetadata, delList, errs)
 			test.errCheck(t, err)
 			assert.Equal(t, test.expectedSkippedCount, len(errs.Skipped()))
 
@@ -2339,7 +2343,7 @@ func (suite *OneDriveCollectionsUnitSuite) TestGet() {
 			// collections we expect it to
 			assert.Equal(t, expectedCollectionCount, collectionCount, "number of collections")
 
-			assert.Equal(t, test.expectedDelList, delList, "del list")
+			test.expectedDelList.AssertEqual(t, delList)
 		})
 	}
 }

src/internal/connector/onedrive/data_collections.go

@@ -4,9 +4,9 @@ import (
 	"context"
 
 	"github.com/alcionai/clues"
-	"golang.org/x/exp/maps"
 
 	"github.com/alcionai/corso/src/internal/common/idname"
+	"github.com/alcionai/corso/src/internal/common/prefixmatcher"
 	"github.com/alcionai/corso/src/internal/connector/graph"
 	"github.com/alcionai/corso/src/internal/connector/support"
 	"github.com/alcionai/corso/src/internal/data"
@@ -44,7 +44,7 @@ func DataCollections(
 	su support.StatusUpdater,
 	ctrlOpts control.Options,
 	errs *fault.Bus,
-) ([]data.BackupCollection, map[string]map[string]struct{}, error) {
+) ([]data.BackupCollection, *prefixmatcher.StringSetMatcher, error) {
 	odb, err := selector.ToOneDriveBackup()
 	if err != nil {
 		return nil, nil, clues.Wrap(err, "parsing selector").WithClues(ctx)
@@ -54,7 +54,7 @@ func DataCollections(
 		el          = errs.Local()
 		categories  = map[path.CategoryType]struct{}{}
 		collections = []data.BackupCollection{}
-		allExcludes = map[string]map[string]struct{}{}
+		ssmb        = prefixmatcher.NewStringSetBuilder()
 	)
 
 	// for each scope that includes oneDrive items, get all
@@ -75,7 +75,7 @@ func DataCollections(
 			su,
 			ctrlOpts)
 
-		odcs, excludes, err := nc.Get(ctx, metadata, errs)
+		odcs, err := nc.Get(ctx, metadata, ssmb, errs)
 		if err != nil {
 			el.AddRecoverable(clues.Stack(err).Label(fault.LabelForceNoBackupCreation))
 		}
@@ -83,14 +83,6 @@ func DataCollections(
 		categories[scope.Category().PathType()] = struct{}{}
 
 		collections = append(collections, odcs...)
-
-		for k, ex := range excludes {
-			if _, ok := allExcludes[k]; !ok {
-				allExcludes[k] = map[string]struct{}{}
-			}
-
-			maps.Copy(allExcludes[k], ex)
-		}
 	}
 
 	mcs, err := migrationCollections(
@@ -123,7 +115,7 @@ func DataCollections(
 		collections = append(collections, baseCols...)
 	}
 
-	return collections, allExcludes, el.Failure()
+	return collections, ssmb.ToReader(), el.Failure()
 }
 
 // adds data migrations to the collection set.

src/internal/connector/onedrive/drive_test.go

@@ -14,6 +14,7 @@ import (
 	"github.com/stretchr/testify/suite"
 
 	"github.com/alcionai/corso/src/internal/common/dttm"
+	"github.com/alcionai/corso/src/internal/common/prefixmatcher"
 	"github.com/alcionai/corso/src/internal/common/ptr"
 	"github.com/alcionai/corso/src/internal/connector/graph"
 	"github.com/alcionai/corso/src/internal/connector/onedrive/api"
@@ -442,10 +443,12 @@ func (suite *OneDriveSuite) TestOneDriveNewCollections() {
 					ToggleFeatures: control.Toggles{},
 				})
 
-			odcs, excludes, err := colls.Get(ctx, nil, fault.New(true))
+			ssmb := prefixmatcher.NewStringSetBuilder()
+
+			odcs, err := colls.Get(ctx, nil, ssmb, fault.New(true))
 			assert.NoError(t, err, clues.ToCore(err))
 			// Don't expect excludes as this isn't an incremental backup.
-			assert.Empty(t, excludes)
+			assert.True(t, ssmb.Empty())
 
 			for _, entry := range odcs {
 				assert.NotEmpty(t, entry.FullPath())

src/internal/connector/sharepoint/data_collections.go

@@ -4,9 +4,9 @@ import (
 	"context"
 
 	"github.com/alcionai/clues"
-	"golang.org/x/exp/maps"
 
 	"github.com/alcionai/corso/src/internal/common/idname"
+	"github.com/alcionai/corso/src/internal/common/prefixmatcher"
 	"github.com/alcionai/corso/src/internal/connector/graph"
 	"github.com/alcionai/corso/src/internal/connector/onedrive"
 	"github.com/alcionai/corso/src/internal/connector/sharepoint/api"
@@ -39,7 +39,7 @@ func DataCollections(
 	su statusUpdater,
 	ctrlOpts control.Options,
 	errs *fault.Bus,
-) ([]data.BackupCollection, map[string]map[string]struct{}, error) {
+) ([]data.BackupCollection, *prefixmatcher.StringSetMatcher, error) {
 	b, err := selector.ToSharePointBackup()
 	if err != nil {
 		return nil, nil, clues.Wrap(err, "sharePointDataCollection: parsing selector")
@@ -54,7 +54,7 @@ func DataCollections(
 		el          = errs.Local()
 		collections = []data.BackupCollection{}
 		categories  = map[path.CategoryType]struct{}{}
-		excluded    = map[string]map[string]struct{}{}
+		ssmb        = prefixmatcher.NewStringSetBuilder()
 	)
 
 	for _, scope := range b.Scopes() {
@@ -86,15 +86,14 @@ func DataCollections(
 			}
 
 		case path.LibrariesCategory:
-			var excludes map[string]map[string]struct{}
-
-			spcs, excludes, err = collectLibraries(
+			spcs, err = collectLibraries(
 				ctx,
 				itemClient,
 				serv,
 				creds.AzureTenantID,
 				site,
 				metadata,
+				ssmb,
 				scope,
 				su,
 				ctrlOpts,
@@ -104,14 +103,6 @@ func DataCollections(
 				continue
 			}
 
-			for prefix, excludes := range excludes {
-				if _, ok := excluded[prefix]; !ok {
-					excluded[prefix] = map[string]struct{}{}
-				}
-
-				maps.Copy(excluded[prefix], excludes)
-			}
-
 		case path.PagesCategory:
 			spcs, err = collectPages(
 				ctx,
@@ -150,7 +141,7 @@ func DataCollections(
 		collections = append(collections, baseCols...)
 	}
 
-	return collections, excluded, el.Failure()
+	return collections, ssmb.ToReader(), el.Failure()
 }
 
 func collectLists(
@@ -208,11 +199,12 @@ func collectLibraries(
 	tenantID string,
 	site idname.Provider,
 	metadata []data.RestoreCollection,
+	ssmb *prefixmatcher.StringSetMatchBuilder,
 	scope selectors.SharePointScope,
 	updater statusUpdater,
 	ctrlOpts control.Options,
 	errs *fault.Bus,
-) ([]data.BackupCollection, map[string]map[string]struct{}, error) {
+) ([]data.BackupCollection, error) {
 	logger.Ctx(ctx).Debug("creating SharePoint Library collections")
 
 	var (
@@ -228,12 +220,12 @@ func collectLibraries(
 			ctrlOpts)
 	)
 
-	odcs, excludes, err := colls.Get(ctx, metadata, errs)
+	odcs, err := colls.Get(ctx, metadata, ssmb, errs)
 	if err != nil {
-		return nil, nil, graph.Wrap(ctx, err, "getting library")
+		return nil, graph.Wrap(ctx, err, "getting library")
 	}
 
-	return append(collections, odcs...), excludes, nil
+	return append(collections, odcs...), nil
 }
 
 // collectPages constructs a sharepoint Collections struct and Get()s the associated

src/internal/kopia/merge_details.go

@@ -114,7 +114,7 @@ type locRefs struct {
 }
 
 type locationPrefixMatcher struct {
-	m prefixmatcher.Matcher[locRefs]
+	m prefixmatcher.Builder[locRefs]
 }
 
 func (m *locationPrefixMatcher) add(

src/internal/kopia/upload.go

@@ -21,6 +21,7 @@ import (
 	"github.com/kopia/kopia/repo/manifest"
 	"github.com/kopia/kopia/snapshot/snapshotfs"
 
+	"github.com/alcionai/corso/src/internal/common/prefixmatcher"
 	"github.com/alcionai/corso/src/internal/connector/graph"
 	"github.com/alcionai/corso/src/internal/connector/graph/metadata"
 	"github.com/alcionai/corso/src/internal/data"
@@ -413,7 +414,7 @@ func streamBaseEntries(
 	locationPath *path.Builder,
 	dir fs.Directory,
 	encodedSeen map[string]struct{},
-	globalExcludeSet map[string]map[string]struct{},
+	globalExcludeSet prefixmatcher.StringSetReader,
 	progress *corsoProgress,
 ) error {
 	if dir == nil {
@@ -421,19 +422,18 @@ func streamBaseEntries(
 	}
 
 	var (
+		longest    string
 		excludeSet map[string]struct{}
-		curPrefix  string
 	)
 
-	ctx = clues.Add(ctx, "current_item_path", curPath)
+	if globalExcludeSet != nil {
+		longest, excludeSet, _ = globalExcludeSet.LongestPrefix(curPath.String())
+	}
 
-	for prefix, excludes := range globalExcludeSet {
-		// Select the set with the longest prefix to be most precise.
-		if strings.HasPrefix(curPath.String(), prefix) && len(prefix) >= len(curPrefix) {
-			excludeSet = excludes
-			curPrefix = prefix
-		}
-	}
+	ctx = clues.Add(
+		ctx,
+		"current_item_path", curPath,
+		"longest_prefix", longest)
 
 	err := dir.IterateEntries(ctx, func(innerCtx context.Context, entry fs.Entry) error {
 		if err := innerCtx.Err(); err != nil {
@@ -521,7 +521,7 @@ func getStreamItemFunc(
 	staticEnts []fs.Entry,
 	streamedEnts data.BackupCollection,
 	baseDir fs.Directory,
-	globalExcludeSet map[string]map[string]struct{},
+	globalExcludeSet prefixmatcher.StringSetReader,
 	progress *corsoProgress,
 ) func(context.Context, func(context.Context, fs.Entry) error) error {
 	return func(ctx context.Context, cb func(context.Context, fs.Entry) error) error {
@@ -569,7 +569,7 @@ func getStreamItemFunc(
 func buildKopiaDirs(
 	dirName string,
 	dir *treeMap,
-	globalExcludeSet map[string]map[string]struct{},
+	globalExcludeSet prefixmatcher.StringSetReader,
 	progress *corsoProgress,
 ) (fs.Directory, error) {
 	// Need to build the directory tree from the leaves up because intermediate
@@ -1053,7 +1053,7 @@ func inflateDirTree(
 	loader snapshotLoader,
 	baseSnaps []IncrementalBase,
 	collections []data.BackupCollection,
-	globalExcludeSet map[string]map[string]struct{},
+	globalExcludeSet prefixmatcher.StringSetReader,
 	progress *corsoProgress,
 ) (fs.Directory, error) {
 	roots, updatedPaths, err := inflateCollectionTree(ctx, collections, progress.toMerge)

src/internal/kopia/upload_test.go

@@ -19,6 +19,7 @@ import (
 	"github.com/stretchr/testify/require"
 	"github.com/stretchr/testify/suite"
 
+	pmMock "github.com/alcionai/corso/src/internal/common/prefixmatcher/mock"
 	exchMock "github.com/alcionai/corso/src/internal/connector/exchange/mock"
 	"github.com/alcionai/corso/src/internal/data"
 	"github.com/alcionai/corso/src/internal/tester"
@@ -708,7 +709,7 @@ func (suite *HierarchyBuilderUnitSuite) TestBuildDirectoryTree() {
 	//       - emails
 	//         - Inbox
 	//           - 42 separate files
-	dirTree, err := inflateDirTree(ctx, nil, nil, collections, nil, progress)
+	dirTree, err := inflateDirTree(ctx, nil, nil, collections, pmMock.NewPrefixMap(nil), progress)
 	require.NoError(t, err, clues.ToCore(err))
 
 	assert.Equal(t, encodeAsPath(testTenant), dirTree.Name())
@@ -805,7 +806,7 @@ func (suite *HierarchyBuilderUnitSuite) TestBuildDirectoryTree_MixedDirectory()
 				errs:    fault.New(true),
 			}
 
-			dirTree, err := inflateDirTree(ctx, nil, nil, test.layout, nil, progress)
+			dirTree, err := inflateDirTree(ctx, nil, nil, test.layout, pmMock.NewPrefixMap(nil), progress)
 			require.NoError(t, err, clues.ToCore(err))
 
 			assert.Equal(t, encodeAsPath(testTenant), dirTree.Name())
@@ -911,7 +912,7 @@ func (suite *HierarchyBuilderUnitSuite) TestBuildDirectoryTree_Fails() {
 				errs:    fault.New(true),
 			}
 
-			_, err := inflateDirTree(ctx, nil, nil, test.layout, nil, progress)
+			_, err := inflateDirTree(ctx, nil, nil, test.layout, pmMock.NewPrefixMap(nil), progress)
 			assert.Error(t, err, clues.ToCore(err))
 		})
 	}
@@ -1027,7 +1028,7 @@ func (suite *HierarchyBuilderUnitSuite) TestBuildDirectoryTreeErrors() {
 				cols = append(cols, mc)
 			}
 
-			_, err := inflateDirTree(ctx, nil, nil, cols, nil, progress)
+			_, err := inflateDirTree(ctx, nil, nil, cols, pmMock.NewPrefixMap(nil), progress)
 			require.Error(t, err, clues.ToCore(err))
 		})
 	}
@@ -1312,9 +1313,8 @@ func (suite *HierarchyBuilderUnitSuite) TestBuildDirectoryTreeSingleSubtree() {
 					mockIncrementalBase("", testTenant, testUser, path.ExchangeService, path.EmailCategory),
 				},
 				test.inputCollections(),
-				nil,
-				progress,
-			)
+				pmMock.NewPrefixMap(nil),
+				progress)
 			require.NoError(t, err, clues.ToCore(err))
 
 			expectTree(t, ctx, test.expected, dirTree)
@@ -1433,7 +1433,7 @@ func (suite *HierarchyBuilderUnitSuite) TestBuildDirectoryTreeMultipleSubdirecto
 	table := []struct {
 		name             string
 		inputCollections func(t *testing.T) []data.BackupCollection
-		inputExcludes    map[string]map[string]struct{}
+		inputExcludes    *pmMock.PrefixMap
 		expected         *expectedNode
 	}{
 		{
@@ -1441,11 +1441,11 @@ func (suite *HierarchyBuilderUnitSuite) TestBuildDirectoryTreeMultipleSubdirecto
 			inputCollections: func(t *testing.T) []data.BackupCollection {
 				return nil
 			},
-			inputExcludes: map[string]map[string]struct{}{
+			inputExcludes: pmMock.NewPrefixMap(map[string]map[string]struct{}{
 				"": {
 					inboxFileName1: {},
 				},
-			},
+			}),
 			expected: expectedTreeWithChildren(
 				[]string{
 					testTenant,
@@ -2229,6 +2229,11 @@ func (suite *HierarchyBuilderUnitSuite) TestBuildDirectoryTreeMultipleSubdirecto
 				snapshotRoot: getBaseSnapshot(),
 			}
 
+			ie := pmMock.NewPrefixMap(nil)
+			if test.inputExcludes != nil {
+				ie = test.inputExcludes
+			}
+
 			dirTree, err := inflateDirTree(
 				ctx,
 				msw,
@@ -2236,7 +2241,7 @@ func (suite *HierarchyBuilderUnitSuite) TestBuildDirectoryTreeMultipleSubdirecto
 					mockIncrementalBase("", testTenant, testUser, path.ExchangeService, path.EmailCategory),
 				},
 				test.inputCollections(t),
-				test.inputExcludes,
+				ie,
 				progress)
 			require.NoError(t, err, clues.ToCore(err))
 
@@ -2400,7 +2405,7 @@ func (suite *HierarchyBuilderUnitSuite) TestBuildDirectoryTreeSkipsDeletedSubtre
 			mockIncrementalBase("", testTenant, testUser, path.ExchangeService, path.EmailCategory),
 		},
 		collections,
-		nil,
+		pmMock.NewPrefixMap(nil),
 		progress)
 	require.NoError(t, err, clues.ToCore(err))
 
@@ -2505,7 +2510,7 @@ func (suite *HierarchyBuilderUnitSuite) TestBuildDirectoryTree_HandleEmptyBase()
 			mockIncrementalBase("", testTenant, testUser, path.ExchangeService, path.EmailCategory),
 		},
 		collections,
-		nil,
+		pmMock.NewPrefixMap(nil),
 		progress)
 	require.NoError(t, err, clues.ToCore(err))
 
@@ -2756,9 +2761,8 @@ func (suite *HierarchyBuilderUnitSuite) TestBuildDirectoryTreeSelectsCorrectSubt
 			mockIncrementalBase("id2", testTenant, testUser, path.ExchangeService, path.EmailCategory),
 		},
 		collections,
-		nil,
-		progress,
-	)
+		pmMock.NewPrefixMap(nil),
+		progress)
 	require.NoError(t, err, clues.ToCore(err))
 
 	expectTree(t, ctx, expected, dirTree)
@@ -2921,7 +2925,7 @@ func (suite *HierarchyBuilderUnitSuite) TestBuildDirectoryTreeSelectsMigrateSubt
 			mockIncrementalBase("id1", testTenant, testUser, path.ExchangeService, path.EmailCategory, path.ContactsCategory),
 		},
 		[]data.BackupCollection{mce, mcc},
-		nil,
+		pmMock.NewPrefixMap(nil),
 		progress)
 	require.NoError(t, err, clues.ToCore(err))
 

src/internal/kopia/wrapper.go

@@ -14,6 +14,7 @@ import (
 	"github.com/kopia/kopia/snapshot/snapshotfs"
 	"github.com/kopia/kopia/snapshot/snapshotmaintenance"
 
+	"github.com/alcionai/corso/src/internal/common/prefixmatcher"
 	"github.com/alcionai/corso/src/internal/data"
 	"github.com/alcionai/corso/src/internal/diagnostics"
 	"github.com/alcionai/corso/src/internal/observe"
@@ -138,7 +139,7 @@ func (w Wrapper) ConsumeBackupCollections(
 	ctx context.Context,
 	previousSnapshots []IncrementalBase,
 	collections []data.BackupCollection,
-	globalExcludeSet map[string]map[string]struct{},
+	globalExcludeSet prefixmatcher.StringSetReader,
 	tags map[string]string,
 	buildTreeWithBase bool,
 	errs *fault.Bus,
@@ -150,7 +151,7 @@ func (w Wrapper) ConsumeBackupCollections(
 	ctx, end := diagnostics.Span(ctx, "kopia:consumeBackupCollections")
 	defer end()
 
-	if len(collections) == 0 && len(globalExcludeSet) == 0 {
+	if len(collections) == 0 && (globalExcludeSet == nil || globalExcludeSet.Empty()) {
 		return &BackupStats{}, &details.Builder{}, nil, nil
 	}
 

src/internal/kopia/wrapper_test.go

@@ -18,6 +18,7 @@ import (
 	"github.com/stretchr/testify/suite"
 	"golang.org/x/exp/maps"
 
+	pmMock "github.com/alcionai/corso/src/internal/common/prefixmatcher/mock"
 	exchMock "github.com/alcionai/corso/src/internal/connector/exchange/mock"
 	"github.com/alcionai/corso/src/internal/connector/onedrive/metadata"
 	"github.com/alcionai/corso/src/internal/data"
@@ -1178,14 +1179,14 @@ func (suite *KopiaSimpleRepoIntegrationSuite) TestBackupExcludeItem() {
 				prefix = itemPath.ToBuilder().Dir().Dir().String()
 			}
 
-			var excluded map[string]map[string]struct{}
+			excluded := pmMock.NewPrefixMap(nil)
 			if test.excludeItem {
-				excluded = map[string]map[string]struct{}{
+				excluded = pmMock.NewPrefixMap(map[string]map[string]struct{}{
 					// Add a prefix if needed.
 					prefix: {
 						itemPath.Item(): {},
 					},
-				}
+				})
 			}
 
 			stats, _, _, err := suite.w.ConsumeBackupCollections(

src/internal/operations/backup.go

@@ -10,6 +10,7 @@ import (
 	"github.com/alcionai/corso/src/internal/common/crash"
 	"github.com/alcionai/corso/src/internal/common/dttm"
 	"github.com/alcionai/corso/src/internal/common/idname"
+	"github.com/alcionai/corso/src/internal/common/prefixmatcher"
 	"github.com/alcionai/corso/src/internal/data"
 	"github.com/alcionai/corso/src/internal/diagnostics"
 	"github.com/alcionai/corso/src/internal/events"
@@ -272,7 +273,7 @@ func (op *BackupOperation) do(
 		}
 	}
 
-	cs, excludes, err := produceBackupDataCollections(
+	cs, ssmb, err := produceBackupDataCollections(
 		ctx,
 		op.bp,
 		op.ResourceOwner,
@@ -294,7 +295,7 @@ func (op *BackupOperation) do(
 		reasons,
 		mans,
 		cs,
-		excludes,
+		ssmb,
 		backupID,
 		op.incremental && canUseMetaData,
 		op.Errors)
@@ -352,7 +353,7 @@ func produceBackupDataCollections(
 	lastBackupVersion int,
 	ctrlOpts control.Options,
 	errs *fault.Bus,
-) ([]data.BackupCollection, map[string]map[string]struct{}, error) {
+) ([]data.BackupCollection, prefixmatcher.StringSetReader, error) {
 	complete, closer := observe.MessageWithCompletion(ctx, "Discovering items to backup")
 	defer func() {
 		complete <- struct{}{}
@@ -424,7 +425,7 @@ func consumeBackupCollections(
 	reasons []kopia.Reason,
 	mans []*kopia.ManifestEntry,
 	cs []data.BackupCollection,
-	excludes map[string]map[string]struct{},
+	pmr prefixmatcher.StringSetReader,
 	backupID model.StableID,
 	isIncremental bool,
 	errs *fault.Bus,
@@ -497,7 +498,7 @@ func consumeBackupCollections(
 		ctx,
 		bases,
 		cs,
-		excludes,
+		pmr,
 		tags,
 		isIncremental,
 		errs)

src/internal/operations/backup_test.go

@@ -14,6 +14,7 @@ import (
 	"github.com/stretchr/testify/require"
 	"github.com/stretchr/testify/suite"
 
+	"github.com/alcionai/corso/src/internal/common/prefixmatcher"
 	"github.com/alcionai/corso/src/internal/connector/mock"
 	"github.com/alcionai/corso/src/internal/data"
 	evmock "github.com/alcionai/corso/src/internal/events/mock"
@@ -98,7 +99,7 @@ func (mbu mockBackupConsumer) ConsumeBackupCollections(
 	ctx context.Context,
 	bases []kopia.IncrementalBase,
 	cs []data.BackupCollection,
-	excluded map[string]map[string]struct{},
+	excluded prefixmatcher.StringSetReader,
 	tags map[string]string,
 	buildTreeWithBase bool,
 	errs *fault.Bus,

src/internal/operations/inject/inject.go

@@ -4,6 +4,7 @@ import (
 	"context"
 
 	"github.com/alcionai/corso/src/internal/common/idname"
+	"github.com/alcionai/corso/src/internal/common/prefixmatcher"
 	"github.com/alcionai/corso/src/internal/data"
 	"github.com/alcionai/corso/src/internal/kopia"
 	"github.com/alcionai/corso/src/pkg/account"
@@ -25,7 +26,7 @@ type (
 			lastBackupVersion int,
 			ctrlOpts control.Options,
 			errs *fault.Bus,
-		) ([]data.BackupCollection, map[string]map[string]struct{}, error)
+		) ([]data.BackupCollection, prefixmatcher.StringSetReader, error)
 
 		Wait() *data.CollectionStats
 	}
@@ -35,7 +36,7 @@ type (
 			ctx context.Context,
 			bases []kopia.IncrementalBase,
 			cs []data.BackupCollection,
-			excluded map[string]map[string]struct{},
+			pmr prefixmatcher.StringSetReader,
 			tags map[string]string,
 			buildTreeWithBase bool,
 			errs *fault.Bus,

src/internal/streamstore/streamstore.go

@@ -9,6 +9,7 @@ import (
 
 	"github.com/alcionai/clues"
 
+	"github.com/alcionai/corso/src/internal/common/prefixmatcher"
 	"github.com/alcionai/corso/src/internal/data"
 	"github.com/alcionai/corso/src/internal/kopia"
 	"github.com/alcionai/corso/src/internal/operations/inject"
@@ -232,7 +233,7 @@ func write(
 		ctx,
 		nil,
 		dbcs,
-		nil,
+		prefixmatcher.NopReader[map[string]struct{}](),
 		nil,
 		false,
 		errs)