diff --git a/api.go b/api.go
index e5562602b..beb2741d0 100644
--- a/api.go
+++ b/api.go
@@ -686,10 +686,10 @@ func (api *API) Import(_ context.Context, req *ImportRequest) error {
 		timestamps[i] = &t
 	}
 
-	// Import columnIDs into notnull field.
-	if err := importNotNullColumns(index, req.ColumnIDs); err != nil {
-		api.server.logger.Printf("import notnull error: index=%s, field=%s, shard=%d, columns=%d, err=%s", req.Index, req.Field, req.Shard, len(req.ColumnIDs), err)
-		return errors.Wrap(err, "importing notnull columns")
+	// Import columnIDs into existence field.
+	if err := importExistenceColumns(index, req.ColumnIDs); err != nil {
+		api.server.logger.Printf("import existence error: index=%s, field=%s, shard=%d, columns=%d, err=%s", req.Index, req.Field, req.Shard, len(req.ColumnIDs), err)
+		return errors.Wrap(err, "importing existence columns")
 	}
 
 	// Import into fragment.
@@ -726,10 +726,10 @@ func (api *API) ImportValue(_ context.Context, req *ImportValueRequest) error {
 		}
 	}
 
-	// Import columnIDs into notnull field.
-	if err := importNotNullColumns(index, req.ColumnIDs); err != nil {
-		api.server.logger.Printf("import notnull error: index=%s, field=%s, shard=%d, columns=%d, err=%s", req.Index, req.Field, req.Shard, len(req.ColumnIDs), err)
-		return errors.Wrap(err, "importing notnull columns")
+	// Import columnIDs into existence field.
+	if err := importExistenceColumns(index, req.ColumnIDs); err != nil {
+		api.server.logger.Printf("import existence error: index=%s, field=%s, shard=%d, columns=%d, err=%s", req.Index, req.Field, req.Shard, len(req.ColumnIDs), err)
+		return errors.Wrap(err, "importing existence columns")
 	}
 
 	// Import into fragment.
@@ -740,14 +740,14 @@ func (api *API) ImportValue(_ context.Context, req *ImportValueRequest) error {
 	return errors.Wrap(err, "importing")
 }
 
-func importNotNullColumns(index *Index, columnIDs []uint64) error {
-	nnf := index.unprotectedNotNullField()
+func importExistenceColumns(index *Index, columnIDs []uint64) error {
+	nnf := index.unprotectedExistenceField()
 	if nnf == nil {
 		return nil
 	}
 
-	notNullRowIDs := make([]uint64, len(columnIDs))
-	return nnf.Import(notNullRowIDs, columnIDs, nil)
+	existenceRowIDs := make([]uint64, len(columnIDs))
+	return nnf.Import(existenceRowIDs, columnIDs, nil)
 }
 
 // MaxShards returns the maximum shard number for each index in a map.
diff --git a/encoding/proto/proto.go b/encoding/proto/proto.go
index c00e71b40..0fcd9df3a 100644
--- a/encoding/proto/proto.go
+++ b/encoding/proto/proto.go
@@ -509,8 +509,8 @@ func encodeCreateIndexMessage(m *pilosa.CreateIndexMessage) *internal.CreateInde
 
 func encodeIndexMeta(m *pilosa.IndexOptions) *internal.IndexMeta {
 	return &internal.IndexMeta{
-		Keys:         m.Keys,
-		TrackNotNull: m.TrackNotNull,
+		Keys:           m.Keys,
+		TrackExistence: m.TrackExistence,
 	}
 }
 
@@ -742,7 +742,7 @@ func decodeCreateIndexMessage(pb *internal.CreateIndexMessage, m *pilosa.CreateI
 
 func decodeIndexMeta(pb *internal.IndexMeta, m *pilosa.IndexOptions) {
 	m.Keys = pb.Keys
-	m.TrackNotNull = pb.TrackNotNull
+	m.TrackExistence = pb.TrackExistence
 }
 
 func decodeDeleteIndexMessage(pb *internal.DeleteIndexMessage, m *pilosa.DeleteIndexMessage) {
diff --git a/executor.go b/executor.go
index 1149f8c0e..5681644aa 100644
--- a/executor.go
+++ b/executor.go
@@ -1131,10 +1131,10 @@ func (e *executor) executeSet(ctx context.Context, index string, c *pql.Call, op
 		return false, ErrFieldNotFound
 	}
 
-	// Set column on not-null field.
-	if nnf := idx.unprotectedNotNullField(); nnf != nil {
+	// Set column on existence field.
+	if nnf := idx.unprotectedExistenceField(); nnf != nil {
 		if _, err := nnf.SetBit(0, colID, nil); err != nil {
-			return false, errors.Wrap(err, "setting not-null column")
+			return false, errors.Wrap(err, "setting existence column")
 		}
 	}
 
diff --git a/executor_test.go b/executor_test.go
index 602be93a5..25465411c 100644
--- a/executor_test.go
+++ b/executor_test.go
@@ -1497,13 +1497,13 @@ func TestExecutor_QueryCall(t *testing.T) {
 	})
 }
 
-// Ensure a notnull field is maintained.
-func TestExecutor_Execute_NotNull(t *testing.T) {
+// Ensure an existence field is maintained.
+func TestExecutor_Execute_Existence(t *testing.T) {
 	t.Run("Row", func(t *testing.T) {
 		c := test.MustRunCluster(t, 1)
 		defer c.Close()
 		hldr := test.Holder{Holder: c[0].Server.Holder()}
-		index := hldr.MustCreateIndexIfNotExists("i", pilosa.IndexOptions{TrackNotNull: true})
+		index := hldr.MustCreateIndexIfNotExists("i", pilosa.IndexOptions{TrackExistence: true})
 		_, err := index.CreateField("f", pilosa.OptFieldTypeDefault())
 		if err != nil {
 			t.Fatal(err)
@@ -1524,26 +1524,26 @@ func TestExecutor_Execute_NotNull(t *testing.T) {
 			t.Fatalf("unexpected columns: %+v", bits)
 		}
 
-		if res, err := c[0].API.Query(context.Background(), &pilosa.QueryRequest{Index: "i", Query: `Row(notnull=0)`}); err != nil {
+		if res, err := c[0].API.Query(context.Background(), &pilosa.QueryRequest{Index: "i", Query: `Row(exists=0)`}); err != nil {
 			t.Fatal(err)
 		} else if bits := res.Results[0].(*pilosa.Row).Columns(); !reflect.DeepEqual(bits, []uint64{3, ShardWidth + 1, ShardWidth + 2}) {
-			t.Fatalf("unexpected notnull columns: %+v", bits)
+			t.Fatalf("unexpected existence columns: %+v", bits)
 		}
 
-		// Reopen cluster to ensure not-null is reloaded.
+		// Reopen cluster to ensure existence field is reloaded.
 		if err := c[0].Reopen(); err != nil {
 			t.Fatal(err)
 		}
 
-		if res, err := c[0].API.Query(context.Background(), &pilosa.QueryRequest{Index: "i", Query: `Row(notnull=0)`}); err != nil {
+		if res, err := c[0].API.Query(context.Background(), &pilosa.QueryRequest{Index: "i", Query: `Row(exists=0)`}); err != nil {
 			t.Fatal(err)
 		} else if bits := res.Results[0].(*pilosa.Row).Columns(); !reflect.DeepEqual(bits, []uint64{3, ShardWidth + 1, ShardWidth + 2}) {
-			t.Fatalf("unexpected notnull columns after reopen: %+v", bits)
+			t.Fatalf("unexpected existence columns after reopen: %+v", bits)
 		}
 	})
 }
 
-func benchmarkNotNull(nn bool, b *testing.B) {
+func benchmarkExistence(nn bool, b *testing.B) {
 	c := test.MustRunCluster(b, 1)
 	defer c.Close()
 	hldr := test.Holder{Holder: c[0].Server.Holder()}
@@ -1551,7 +1551,7 @@ func benchmarkNotNull(nn bool, b *testing.B) {
 	indexName := "i"
 	fieldName := "f"
 
-	index := hldr.MustCreateIndexIfNotExists(indexName, pilosa.IndexOptions{TrackNotNull: nn})
+	index := hldr.MustCreateIndexIfNotExists(indexName, pilosa.IndexOptions{TrackExistence: nn})
 	// Create field.
 	if _, err := index.CreateFieldIfNotExists(fieldName); err != nil {
 		b.Fatal(err)
@@ -1568,5 +1568,5 @@ func benchmarkNotNull(nn bool, b *testing.B) {
 	}
 }
 
-func BenchmarkExecutor_NotNull_True(b *testing.B)  { benchmarkNotNull(true, b) }
-func BenchmarkExecutor_NotNull_False(b *testing.B) { benchmarkNotNull(false, b) }
+func BenchmarkExecutor_Existence_True(b *testing.B)  { benchmarkExistence(true, b) }
+func BenchmarkExecutor_Existence_False(b *testing.B) { benchmarkExistence(false, b) }
diff --git a/holder.go b/holder.go
index 252fca2db..794104e53 100644
--- a/holder.go
+++ b/holder.go
@@ -39,8 +39,8 @@ const (
 	// fileLimit is the maximum open file limit (ulimit -n) to automatically set.
 	fileLimit = 262144 // (512^2)
 
-	// notNullFieldName is the name of the internal field used to store not-null values.
-	notNullFieldName = "notnull" // TODO: use a name less likely to collide?
+	// existenceFieldName is the name of the internal field used to store existence values.
+	existenceFieldName = "exists"
 )
 
 // Holder represents a container for indexes.
@@ -357,7 +357,7 @@ func (h *Holder) createIndex(name string, opt IndexOptions) (*Index, error) {
 	}
 
 	index.keys = opt.Keys
-	index.trackNotNull = opt.TrackNotNull
+	index.trackExistence = opt.TrackExistence
 
 	if err := index.Open(); err != nil {
 		return nil, errors.Wrap(err, "opening")
diff --git a/http/client_test.go b/http/client_test.go
index 33a452f7b..f0e8cf132 100644
--- a/http/client_test.go
+++ b/http/client_test.go
@@ -655,8 +655,8 @@ func TestClient_ImportValue(t *testing.T) {
 	}
 }
 
-// Ensure client can bulk import data while tracking notnull.
-func TestClient_ImportNotNull(t *testing.T) {
+// Ensure client can bulk import data while tracking existence.
+func TestClient_ImportExistence(t *testing.T) {
 	cmd := test.MustRunCluster(t, 1)[0]
 	host := cmd.URL()
 	holder := cmd.Server.Holder()
@@ -666,7 +666,7 @@ func TestClient_ImportNotNull(t *testing.T) {
 		idxName := "iset"
 		fldName := "fset"
 
-		index := hldr.MustCreateIndexIfNotExists(idxName, pilosa.IndexOptions{TrackNotNull: true})
+		index := hldr.MustCreateIndexIfNotExists(idxName, pilosa.IndexOptions{TrackExistence: true})
 		_, err := index.CreateFieldIfNotExists(fldName)
 		if err != nil {
 			t.Fatal(err)
@@ -690,9 +690,9 @@ func TestClient_ImportNotNull(t *testing.T) {
 			t.Fatalf("unexpected columns: %+v", a)
 		}
 
-		// Verify notnull.
-		if a := hldr.Row(idxName, "notnull", 0).Columns(); !reflect.DeepEqual(a, []uint64{1, 5, 6}) {
-			t.Fatalf("unexpected notnull columns: %+v", a)
+		// Verify existence.
+		if a := hldr.ReadRow(idxName, "exists", 0).Columns(); !reflect.DeepEqual(a, []uint64{1, 5, 6}) {
+			t.Fatalf("unexpected existence columns: %+v", a)
 		}
 	})
 
@@ -700,7 +700,7 @@ func TestClient_ImportNotNull(t *testing.T) {
 		idxName := "iint"
 		fldName := "fint"
 
-		index := hldr.MustCreateIndexIfNotExists(idxName, pilosa.IndexOptions{TrackNotNull: true})
+		index := hldr.MustCreateIndexIfNotExists(idxName, pilosa.IndexOptions{TrackExistence: true})
 		field, err := index.CreateFieldIfNotExists(fldName, pilosa.OptFieldTypeInt(-100, 100))
 		if err != nil {
 			t.Fatal(err)
@@ -725,9 +725,9 @@ func TestClient_ImportNotNull(t *testing.T) {
 			t.Fatalf("unexpected values: got sum=%v, count=%v; expected sum=50, cnt=3", sum, cnt)
 		}
 
-		// Verify notnull.
-		if a := hldr.Row(idxName, "notnull", 0).Columns(); !reflect.DeepEqual(a, []uint64{1, 2, 3}) {
-			t.Fatalf("unexpected notnull columns: %+v", a)
+		// Verify existence.
+		if a := hldr.ReadRow(idxName, "exists", 0).Columns(); !reflect.DeepEqual(a, []uint64{1, 2, 3}) {
+			t.Fatalf("unexpected existence columns: %+v", a)
 		}
 	})
 }
diff --git a/index.go b/index.go
index cccf2de69..a78fd8365 100644
--- a/index.go
+++ b/index.go
@@ -37,8 +37,8 @@ type Index struct {
 	keys bool // use string keys
 
 	// Not-null tracking.
-	trackNotNull bool
-	notNullField *Field
+	trackExistence bool
+	existenceField *Field
 
 	// Fields by name.
 	fields map[string]*Field
@@ -96,8 +96,8 @@ func (i *Index) Options() IndexOptions {
 
 func (i *Index) options() IndexOptions {
 	return IndexOptions{
-		Keys:         i.keys,
-		TrackNotNull: i.trackNotNull,
+		Keys:           i.keys,
+		TrackExistence: i.trackExistence,
 	}
 }
 
@@ -117,9 +117,9 @@ func (i *Index) Open() error {
 		return errors.Wrap(err, "opening fields")
 	}
 
-	if i.trackNotNull {
-		if err := i.openNotNullField(); err != nil {
-			return errors.Wrap(err, "opening not-null field")
+	if i.trackExistence {
+		if err := i.openExistenceField(); err != nil {
+			return errors.Wrap(err, "opening existence field")
 		}
 	}
 
@@ -160,13 +160,13 @@ func (i *Index) openFields() error {
 	return nil
 }
 
-// openNotNullField gets or creates the not-null field and associates it to the index.
-func (i *Index) openNotNullField() error {
-	f, err := i.createFieldIfNotExists(notNullFieldName, FieldOptions{CacheType: CacheTypeNone, CacheSize: 0})
+// openExistenceField gets or creates the existence field and associates it to the index.
+func (i *Index) openExistenceField() error {
+	f, err := i.createFieldIfNotExists(existenceFieldName, FieldOptions{CacheType: CacheTypeNone, CacheSize: 0})
 	if err != nil {
-		return errors.Wrap(err, "creating not-null field")
+		return errors.Wrap(err, "creating existence field")
 	}
-	i.notNullField = f
+	i.existenceField = f
 	return nil
 }
 
@@ -188,7 +188,7 @@ func (i *Index) loadMeta() error {
 
 	// Copy metadata fields.
 	i.keys = pb.Keys
-	i.trackNotNull = pb.TrackNotNull
+	i.trackExistence = pb.TrackExistence
 
 	return nil
 }
@@ -197,8 +197,8 @@ func (i *Index) loadMeta() error {
 func (i *Index) saveMeta() error {
 	// Marshal metadata.
 	buf, err := proto.Marshal(&internal.IndexMeta{
-		Keys:         i.keys,
-		TrackNotNull: i.trackNotNull,
+		Keys:           i.keys,
+		TrackExistence: i.trackExistence,
 	})
 	if err != nil {
 		return errors.Wrap(err, "marshalling")
@@ -275,9 +275,9 @@ func (i *Index) Fields() []*Field {
 	return a
 }
 
-// unprotectedNotNullField returns the internal field used to track not-null columns.
-func (i *Index) unprotectedNotNullField() *Field {
-	return i.notNullField
+// unprotectedExistenceField returns the internal field used to track column existence.
+func (i *Index) unprotectedExistenceField() *Field {
+	return i.existenceField
 }
 
 // recalculateCaches recalculates caches on every field in the index.
@@ -448,8 +448,8 @@ func (p indexInfoSlice) Less(i, j int) bool { return p[i].Name < p[j].Name }
 
 // IndexOptions represents options to set when initializing an index.
 type IndexOptions struct {
-	Keys         bool `json:"keys"`
-	TrackNotNull bool `json:"trackNotNull"`
+	Keys           bool `json:"keys"`
+	TrackExistence bool `json:"trackExistence"`
 }
 
 // hasTime returns true if a contains a non-nil time.
diff --git a/internal/private.pb.go b/internal/private.pb.go
index 2d1c0deef..c65049d51 100644
--- a/internal/private.pb.go
+++ b/internal/private.pb.go
@@ -62,8 +62,8 @@ var _ = math.Inf
 const _ = proto.ProtoPackageIsVersion2 // please upgrade the proto package
 
 type IndexMeta struct {
-	Keys         bool `protobuf:"varint,3,opt,name=Keys,proto3" json:"Keys,omitempty"`
-	TrackNotNull bool `protobuf:"varint,4,opt,name=TrackNotNull,proto3" json:"TrackNotNull,omitempty"`
+	Keys           bool `protobuf:"varint,3,opt,name=Keys,proto3" json:"Keys,omitempty"`
+	TrackExistence bool `protobuf:"varint,4,opt,name=TrackExistence,proto3" json:"TrackExistence,omitempty"`
 }
 
 func (m *IndexMeta) Reset()                    { *m = IndexMeta{} }
@@ -78,9 +78,9 @@ func (m *IndexMeta) GetKeys() bool {
 	return false
 }
 
-func (m *IndexMeta) GetTrackNotNull() bool {
+func (m *IndexMeta) GetTrackExistence() bool {
 	if m != nil {
-		return m.TrackNotNull
+		return m.TrackExistence
 	}
 	return false
 }
@@ -1059,10 +1059,10 @@ func (m *IndexMeta) MarshalTo(dAtA []byte) (int, error) {
 		}
 		i++
 	}
-	if m.TrackNotNull {
+	if m.TrackExistence {
 		dAtA[i] = 0x20
 		i++
-		if m.TrackNotNull {
+		if m.TrackExistence {
 			dAtA[i] = 1
 		} else {
 			dAtA[i] = 0
@@ -2318,7 +2318,7 @@ func (m *IndexMeta) Size() (n int) {
 	if m.Keys {
 		n += 2
 	}
-	if m.TrackNotNull {
+	if m.TrackExistence {
 		n += 2
 	}
 	return n
@@ -2925,7 +2925,7 @@ func (m *IndexMeta) Unmarshal(dAtA []byte) error {
 			m.Keys = bool(v != 0)
 		case 4:
 			if wireType != 0 {
-				return fmt.Errorf("proto: wrong wireType = %d for field TrackNotNull", wireType)
+				return fmt.Errorf("proto: wrong wireType = %d for field TrackExistence", wireType)
 			}
 			var v int
 			for shift := uint(0); ; shift += 7 {
@@ -2942,7 +2942,7 @@ func (m *IndexMeta) Unmarshal(dAtA []byte) error {
 					break
 				}
 			}
-			m.TrackNotNull = bool(v != 0)
+			m.TrackExistence = bool(v != 0)
 		default:
 			iNdEx = preIndex
 			skippy, err := skipPrivate(dAtA[iNdEx:])
@@ -7184,74 +7184,74 @@ var (
 func init() { proto.RegisterFile("private.proto", fileDescriptorPrivate) }
 
 var fileDescriptorPrivate = []byte{
-	// 1093 bytes of a gzipped FileDescriptorProto
+	// 1095 bytes of a gzipped FileDescriptorProto
 	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0xac, 0x56, 0xdd, 0x6e, 0xdc, 0x44,
-	0x14, 0xc6, 0x3f, 0xbb, 0xd9, 0x3d, 0x9b, 0x4d, 0x13, 0x97, 0x06, 0x17, 0xa1, 0x10, 0x46, 0x95,
-	0x1a, 0x2a, 0x11, 0xaa, 0xf6, 0x86, 0xbf, 0x4a, 0x25, 0xbb, 0x01, 0x4c, 0x49, 0x28, 0xe3, 0x24,
-	0x77, 0xbd, 0x98, 0xec, 0x8e, 0x1a, 0x2b, 0x5e, 0x8f, 0xb1, 0xc7, 0x49, 0xb6, 0x17, 0xdc, 0x82,
-	0xc4, 0x0b, 0x20, 0x9e, 0x84, 0x47, 0xe0, 0x92, 0x47, 0x40, 0xe1, 0x45, 0xd0, 0x9c, 0x19, 0xff,
-	0x64, 0xb3, 0x21, 0x55, 0xe8, 0xdd, 0x9c, 0xef, 0x9c, 0x39, 0xe7, 0x9b, 0xf3, 0x67, 0x43, 0x3f,
-	0xcd, 0xa2, 0x13, 0x26, 0xf9, 0x66, 0x9a, 0x09, 0x29, 0xbc, 0x4e, 0x94, 0x48, 0x9e, 0x25, 0x2c,
-	0x26, 0x03, 0xe8, 0x06, 0xc9, 0x98, 0x9f, 0xed, 0x70, 0xc9, 0x3c, 0x0f, 0xdc, 0x67, 0x7c, 0x9a,
-	0xfb, 0xce, 0xba, 0xb5, 0xd1, 0xa1, 0x78, 0xf6, 0x08, 0x2c, 0xee, 0x65, 0x6c, 0x74, 0xbc, 0x2b,
-	0xe4, 0x6e, 0x11, 0xc7, 0xbe, 0x8b, 0xba, 0x0b, 0x18, 0xf9, 0xc3, 0x82, 0xc5, 0xaf, 0x22, 0x1e,
-	0x8f, 0xbf, 0x4f, 0x65, 0x24, 0x92, 0xdc, 0x7b, 0x0f, 0xba, 0x03, 0x36, 0x3a, 0xe2, 0x7b, 0xd3,
-	0x94, 0xa3, 0xb7, 0x2e, 0xad, 0x81, 0x4a, 0x1b, 0x46, 0xaf, 0x38, 0xfa, 0xeb, 0xd3, 0x1a, 0xf0,
-	0xd6, 0xa1, 0xb7, 0x17, 0x4d, 0xf8, 0x0f, 0x05, 0x4b, 0x64, 0x31, 0xf1, 0x5b, 0x78, 0xbb, 0x09,
-	0x29, 0x9a, 0xe8, 0xb8, 0x83, 0x2a, 0x3c, 0x7b, 0xcb, 0xe0, 0xec, 0x44, 0x89, 0xdf, 0x5d, 0xb7,
-	0x36, 0x1c, 0xaa, 0x8e, 0x88, 0xb0, 0x33, 0x1f, 0x0c, 0xc2, 0xce, 0xaa, 0xe7, 0xf5, 0xea, 0xe7,
-	0x11, 0x02, 0x4b, 0xc1, 0x24, 0x15, 0x99, 0xa4, 0x3c, 0x4f, 0x45, 0x92, 0xa3, 0xa7, 0xed, 0x2c,
-	0xf3, 0x2d, 0x74, 0xae, 0x8e, 0xe4, 0x27, 0x58, 0xde, 0x8a, 0xc5, 0xe8, 0x78, 0xc8, 0x24, 0xa3,
-	0xfc, 0xc7, 0x82, 0xe7, 0xd2, 0x7b, 0x1b, 0x5a, 0x98, 0x37, 0x63, 0xa7, 0x05, 0x85, 0x62, 0x1e,
-	0x7c, 0x5b, 0xa3, 0x28, 0x28, 0x14, 0xef, 0x63, 0x26, 0x5c, 0xaa, 0x05, 0x85, 0x86, 0x47, 0x2c,
-	0x1b, 0x63, 0x06, 0x5c, 0xaa, 0x05, 0xc5, 0xf1, 0x20, 0xe2, 0xa7, 0xe6, 0xd9, 0x78, 0x26, 0x01,
-	0xac, 0x34, 0xe2, 0x1b, 0x9a, 0xab, 0xd0, 0xa6, 0xe2, 0x34, 0x18, 0xe6, 0xbe, 0xb5, 0xee, 0x6c,
-	0xb8, 0xd4, 0x48, 0x98, 0x5c, 0x11, 0x17, 0x93, 0x44, 0xa9, 0x6c, 0x54, 0xd5, 0x00, 0xb9, 0x0b,
-	0x2d, 0xcc, 0xb4, 0x7a, 0x65, 0x7d, 0x57, 0x1d, 0xc9, 0xcf, 0x16, 0x74, 0x77, 0xd8, 0x19, 0xd2,
-	0xc8, 0xbd, 0x27, 0xd0, 0x09, 0x25, 0x4b, 0xc6, 0x8a, 0xa0, 0x32, 0xea, 0x3d, 0xfa, 0x60, 0xb3,
-	0x6c, 0x9a, 0xcd, 0xca, 0x6c, 0xb3, 0xb4, 0xd9, 0x4e, 0x64, 0x36, 0xa5, 0xd5, 0x95, 0x77, 0x3f,
-	0x87, 0xfe, 0x05, 0x95, 0x8a, 0x77, 0xcc, 0xa7, 0x65, 0x56, 0x8f, 0xf9, 0x54, 0xbd, 0xff, 0x84,
-	0xc5, 0x05, 0xc7, 0x5c, 0xb9, 0x54, 0x0b, 0x9f, 0xd9, 0x9f, 0x58, 0xe4, 0x00, 0xbc, 0x41, 0xc6,
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-	0x62, 0x55, 0x07, 0xa7, 0x51, 0x07, 0xf2, 0x00, 0xbc, 0x21, 0x8f, 0xb9, 0xe4, 0xa6, 0xe3, 0xff,
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+	0x0f, 0xa0, 0x37, 0x3d, 0x9d, 0x97, 0x4d, 0x9b, 0x26, 0xde, 0x03, 0x58, 0x08, 0x45, 0x91, 0x0d,
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+	0x78, 0x3c, 0xd5, 0x4a, 0x7e, 0x1b, 0x2f, 0xbc, 0x53, 0x5f, 0xb8, 0xa0, 0xa6, 0x17, 0xad, 0xc9,
+	0x2f, 0x16, 0xdc, 0x68, 0x52, 0x78, 0xad, 0xc1, 0xad, 0x2a, 0x62, 0xcf, 0xac, 0x88, 0x33, 0xab,
+	0x22, 0x6e, 0x5d, 0x91, 0xfa, 0xc3, 0xdc, 0x6a, 0x7c, 0x98, 0xc9, 0x31, 0xdc, 0xb9, 0x54, 0xa6,
+	0x2d, 0x31, 0x4e, 0x55, 0x3f, 0xfc, 0x8f, 0x72, 0xa9, 0x95, 0x96, 0x65, 0xa6, 0x50, 0x5d, 0xaa,
+	0x05, 0xf2, 0x19, 0xdc, 0x0e, 0xb9, 0x6c, 0x14, 0xa9, 0xec, 0xb6, 0x35, 0x70, 0x76, 0xf9, 0xe9,
+	0x15, 0xcf, 0x57, 0x2a, 0xf2, 0x25, 0xf8, 0xfb, 0xe9, 0x88, 0x49, 0x7e, 0xad, 0xdb, 0x9b, 0xd0,
+	0xd9, 0x13, 0xa9, 0x88, 0xc5, 0xcb, 0xc9, 0x9c, 0xa9, 0xf7, 0x61, 0x41, 0xef, 0x6f, 0xbd, 0x46,
+	0xba, 0xb4, 0x14, 0xc9, 0x2d, 0xd5, 0xd0, 0x43, 0x16, 0x0f, 0x8b, 0x58, 0xd1, 0x50, 0x3f, 0x6d,
+	0xf9, 0xe6, 0xd2, 0x9f, 0xe7, 0xab, 0xd6, 0x5f, 0xe7, 0xab, 0xd6, 0xdf, 0xe7, 0xab, 0xd6, 0x6f,
+	0xff, 0xac, 0xbe, 0x75, 0xd8, 0xc6, 0x9f, 0xfa, 0x47, 0xff, 0x06, 0x00, 0x00, 0xff, 0xff, 0x31,
+	0x07, 0xf3, 0xac, 0xe5, 0x0b, 0x00, 0x00,
 }
diff --git a/internal/private.proto b/internal/private.proto
index 1e97e29bc..88d16363f 100644
--- a/internal/private.proto
+++ b/internal/private.proto
@@ -4,7 +4,7 @@ package internal;
 
 message IndexMeta {
 	bool Keys = 3;
-	bool TrackNotNull = 4;
+	bool TrackExistence = 4;
 }
 
 message FieldOptions {
diff --git a/pilosa.go b/pilosa.go
index 45d77a9f3..7378eb628 100644
--- a/pilosa.go
+++ b/pilosa.go
@@ -49,6 +49,8 @@ var (
 	ErrName  = errors.New("invalid index or field name, must match [a-z0-9_-]")
 	ErrLabel = errors.New("invalid row or column label, must match [A-Za-z0-9_-]")
 
+	ErrReservedName = errors.New("reserved index or field name")
+
 	// ErrFragmentNotFound is returned when a fragment does not exist.
 	ErrFragmentNotFound = errors.New("fragment not found")
 	ErrQueryRequired    = errors.New("query required")
@@ -125,6 +127,9 @@ const TimeFormat = "2006-01-02T15:04"
 
 // validateName ensures that the name is a valid format.
 func validateName(name string) error {
+	if name == existenceFieldName {
+		return ErrReservedName
+	}
 	if !nameRegexp.Match([]byte(name)) {
 		return ErrName
 	}
diff --git a/pilosa_internal_test.go b/pilosa_internal_test.go
index 139d5c2b7..96dae1433 100644
--- a/pilosa_internal_test.go
+++ b/pilosa_internal_test.go
@@ -34,6 +34,7 @@ func TestValidateNameInvalid(t *testing.T) {
 	names := []string{
 		"", "'", "^", "/", "\\", "A", "*", "a:b", "valid?no", "yüce", "1", "_", "-",
 		"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa1",
+		"exists",
 	}
 	for _, name := range names {
 		if validateName(name) == nil {
diff --git a/test/holder.go b/test/holder.go
index 80778fe2a..8d080e493 100644
--- a/test/holder.go
+++ b/test/holder.go
@@ -91,6 +91,20 @@ func (h *Holder) Row(index, field string, rowID uint64) *pilosa.Row {
 	return row
 }
 
+// ReadRow returns a Row for a given field. If the field does not exist,
+// it panics rather than creating the field.
+func (h *Holder) ReadRow(index, field string, rowID uint64) *pilosa.Row {
+	f := h.Holder.Field(index, field)
+	if f == nil {
+		panic(pilosa.ErrFieldNotFound)
+	}
+	row, err := f.Row(rowID)
+	if err != nil {
+		panic(err)
+	}
+	return row
+}
+
 func (h *Holder) RowAttrStore(index, field string) pilosa.AttrStore {
 	idx := h.MustCreateIndexIfNotExists(index, pilosa.IndexOptions{})
 	f, err := idx.CreateFieldIfNotExists(field, pilosa.OptFieldTypeDefault())