add test case for seeing prefix iterators outside of range

similar to #256 except for prefix iterators
includes fix for boltdb and gtreap which had incorrect behavior

index/store/boltdb/iterator.go

@@ -39,9 +39,17 @@ func (i *Iterator) updateValid() {
 }
 
 func (i *Iterator) Seek(k []byte) {
-	if bytes.Compare(k, i.start) < 0 {
+	if i.start != nil && bytes.Compare(k, i.start) < 0 {
 		k = i.start
 	}
+	if i.prefix != nil && !bytes.HasPrefix(k, i.prefix) {
+		if bytes.Compare(k, i.prefix) < 0 {
+			k = i.prefix
+		} else {
+			i.valid = false
+			return
+		}
+	}
 	i.key, i.val = i.cursor.Seek(k)
 	i.updateValid()
 }

index/store/boltdb/store_test.go

@@ -66,6 +66,12 @@ func TestBoltDBPrefixIterator(t *testing.T) {
 	test.CommonTestPrefixIterator(t, s)
 }
 
+func TestBoltDBPrefixIteratorSeek(t *testing.T) {
+	s := open(t, nil)
+	defer cleanup(t, s)
+	test.CommonTestPrefixIteratorSeek(t, s)
+}
+
 func TestBoltDBRangeIterator(t *testing.T) {
 	s := open(t, nil)
 	defer cleanup(t, s)

index/store/goleveldb/store_test.go

@@ -69,6 +69,12 @@ func TestGoLevelDBPrefixIterator(t *testing.T) {
 	test.CommonTestPrefixIterator(t, s)
 }
 
+func TestGoLevelDBPrefixIteratorSeek(t *testing.T) {
+	s := open(t, nil)
+	defer cleanup(t, s)
+	test.CommonTestPrefixIteratorSeek(t, s)
+}
+
 func TestGoLevelDBRangeIterator(t *testing.T) {
 	s := open(t, nil)
 	defer cleanup(t, s)

index/store/gtreap/iterator.go

@@ -36,9 +36,26 @@ type Iterator struct {
 }
 
 func (w *Iterator) Seek(k []byte) {
-	if bytes.Compare(k, w.start) < 0 {
+	if w.start != nil && bytes.Compare(k, w.start) < 0 {
 		k = w.start
 	}
+	if w.prefix != nil && !bytes.HasPrefix(k, w.prefix) {
+		if bytes.Compare(k, w.prefix) < 0 {
+			k = w.prefix
+		} else {
+			var end []byte
+			for i := len(w.prefix) - 1; i >= 0; i-- {
+				c := w.prefix[i]
+				if c < 0xff {
+					end = make([]byte, i+1)
+					copy(end, w.prefix)
+					end[i] = c + 1
+					break
+				}
+			}
+			k = end
+		}
+	}
 	w.restart(&Item{k: k})
 }
 

index/store/gtreap/store_test.go

@@ -64,6 +64,12 @@ func TestGTreapPrefixIterator(t *testing.T) {
 	test.CommonTestPrefixIterator(t, s)
 }
 
+func TestGTreapPrefixIteratorSeek(t *testing.T) {
+	s := open(t, nil)
+	defer cleanup(t, s)
+	test.CommonTestPrefixIteratorSeek(t, s)
+}
+
 func TestGTreapRangeIterator(t *testing.T) {
 	s := open(t, nil)
 	defer cleanup(t, s)

index/store/metrics/store_test.go

@@ -53,6 +53,12 @@ func TestMetricsPrefixIterator(t *testing.T) {
 	test.CommonTestPrefixIterator(t, s)
 }
 
+func TestMetricsPrefixIteratorSeek(t *testing.T) {
+	s := open(t, nil)
+	defer cleanup(t, s)
+	test.CommonTestPrefixIteratorSeek(t, s)
+}
+
 func TestMetricsRangeIterator(t *testing.T) {
 	s := open(t, nil)
 	defer cleanup(t, s)

index/store/test/iterator.go

@@ -131,6 +131,74 @@ func CommonTestPrefixIterator(t *testing.T, s store.KVStore) {
 	}
 }
 
+func CommonTestPrefixIteratorSeek(t *testing.T, s store.KVStore) {
+
+	data := []testRow{
+		{[]byte("a"), []byte("val")},
+		{[]byte("b1"), []byte("val")},
+		{[]byte("b2"), []byte("val")},
+		{[]byte("b3"), []byte("val")},
+		{[]byte("c"), []byte("val")},
+	}
+
+	err := batchWriteRows(s, data)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// open a reader
+	reader, err := s.Reader()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// get an iterator on a central subset of the data
+	iter := reader.PrefixIterator([]byte("b"))
+
+	// check that all keys have prefix
+	found := []string{}
+	for ; iter.Valid(); iter.Next() {
+		found = append(found, string(iter.Key()))
+	}
+	for _, f := range found {
+		if !strings.HasPrefix(f, "b") {
+			t.Errorf("got key '%s' that doesn't have correct prefix")
+		}
+	}
+	if len(found) != 3 {
+		t.Errorf("expected 3 keys with prefix, got %d", len(found))
+	}
+
+	// now try to seek before the prefix and repeat
+	found = []string{}
+	for iter.Seek([]byte("a")); iter.Valid(); iter.Next() {
+		found = append(found, string(iter.Key()))
+	}
+	for _, f := range found {
+		if !strings.HasPrefix(f, "b") {
+			t.Errorf("got key '%s' that doesn't have correct prefix")
+		}
+	}
+	if len(found) != 3 {
+		t.Errorf("expected 3 keys with prefix, got %d", len(found))
+	}
+
+	// now try to seek after the prefix and repeat
+	found = []string{}
+	for iter.Seek([]byte("c")); iter.Valid(); iter.Next() {
+		found = append(found, string(iter.Key()))
+	}
+	for _, f := range found {
+		if !strings.HasPrefix(f, "b") {
+			t.Errorf("got key '%s' that doesn't have correct prefix")
+		}
+	}
+	if len(found) != 0 {
+		t.Errorf("expected 0 keys with prefix, got %d", len(found))
+	}
+
+}
+
 func CommonTestRangeIterator(t *testing.T, s store.KVStore) {
 
 	data := []testRow{