Add a Compact() function to gtreap store.

index/store/gtreap/store.go

@@ -77,6 +77,41 @@ func (s *Store) Writer() (store.KVWriter, error) {
 	return &Writer{s: s}, nil
 }
 
+// Compact removes DictionaryTerm entries with a count of zero.
+// This is a workaround for github issue #374.
+func (s *Store) Compact() (err error) {
+	kvreader, err := s.Reader()
+	if err != nil {
+		return err
+	}
+
+	defer func() {
+		if cerr := kvreader.Close(); err == nil && cerr != nil {
+			err = cerr
+		}
+	}()
+
+	prefix := []byte("d")
+
+	s.m.Lock()
+	defer s.m.Unlock()
+	it := kvreader.PrefixIterator(prefix)
+	defer func() {
+		if cerr := it.Close(); err == nil && cerr != nil {
+			err = cerr
+		}
+	}()
+
+	for ; it.Valid(); it.Next() {
+		k, v, _ := it.Current()
+		if bytes.Equal(v, []byte{0}) {
+			s.t = s.t.Delete(&Item{k: k})
+		}
+	}
+
+	return
+}
+
 func init() {
 	registry.RegisterKVStore(Name, New)
 }

index/store/gtreap/store_test.go

@@ -15,6 +15,7 @@
 package gtreap
 
 import (
+	"bytes"
 	"testing"
 
 	"github.com/blevesearch/bleve/index/store"
@@ -91,3 +92,67 @@ func TestGTreapMerge(t *testing.T) {
 	defer cleanup(t, s)
 	test.CommonTestMerge(t, s)
 }
+
+func TestGTreapCompact(t *testing.T) {
+	s := open(t, nil)
+	defer cleanup(t, s)
+
+	writer, err := s.Writer()
+	if err != nil {
+		t.Error(err)
+	}
+
+	batch := writer.NewBatch()
+	// Should preserve non-dictionary row (key doesn't start with 'd').
+	batch.Set([]byte("a1"), []byte{0})
+	// Should delete for dictionary row with zero reference.
+	batch.Set([]byte("d1"), []byte{0})
+	batch.Set([]byte("d2"), []byte{0})
+	// Should preserve for dictionary row with non-zero reference.
+	batch.Set([]byte("d3"), []byte{1})
+
+	err = writer.ExecuteBatch(batch)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = writer.Close()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	validate(t, s, []byte("a1"), []byte{0})
+	validate(t, s, []byte("d1"), []byte{0})
+	validate(t, s, []byte("d2"), []byte{0})
+	validate(t, s, []byte("d3"), []byte{1})
+
+	if err := s.(*Store).Compact(); err != nil {
+		t.Fatal(err)
+	}
+
+	validate(t, s, []byte("a1"), []byte{0})
+	validate(t, s, []byte("d1"), nil)
+	validate(t, s, []byte("d2"), nil)
+	validate(t, s, []byte("d3"), []byte{1})
+}
+
+func validate(t *testing.T, s store.KVStore, key []byte, value []byte) {
+	reader, err := s.Reader()
+	if err != nil {
+		t.Error(err)
+	}
+	defer func() {
+		err := reader.Close()
+		if err != nil {
+			t.Fatal(err)
+		}
+	}()
+
+	got, err := reader.Get(key)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !bytes.Equal(got, value) {
+		t.Errorf("key %v value got %v, want %v", string(key), got, value)
+	}
+}