Adding upstream version 2.5.1.

Signed-off-by: Daniel Baumann <daniel@debian.org>

analysis/token/snowball/snowball.go

@@ -0,0 +1,62 @@
+//  Copyright (c) 2014 Couchbase, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 		http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package snowball
+
+import (
+	"fmt"
+
+	"github.com/blevesearch/bleve/v2/analysis"
+	"github.com/blevesearch/bleve/v2/registry"
+
+	"github.com/blevesearch/snowball"
+)
+
+const Name = "stemmer_snowball"
+
+type SnowballStemmer struct {
+	language string
+}
+
+func NewSnowballStemmer(language string) *SnowballStemmer {
+	return &SnowballStemmer{
+		language: language,
+	}
+}
+
+func (s *SnowballStemmer) Filter(input analysis.TokenStream) analysis.TokenStream {
+	for _, token := range input {
+		// if it is not a protected keyword, stem it
+		if !token.KeyWord {
+			stemmed, _ := snowball.Stem(string(token.Term), s.language, true)
+			token.Term = []byte(stemmed)
+		}
+	}
+	return input
+}
+
+func SnowballStemmerConstructor(config map[string]interface{}, cache *registry.Cache) (analysis.TokenFilter, error) {
+	language, ok := config["language"].(string)
+	if !ok {
+		return nil, fmt.Errorf("must specify language")
+	}
+	return NewSnowballStemmer(language), nil
+}
+
+func init() {
+	err := registry.RegisterTokenFilter(Name, SnowballStemmerConstructor)
+	if err != nil {
+		panic(err)
+	}
+}

analysis/token/snowball/snowball_test.go

@@ -0,0 +1,115 @@
+//  Copyright (c) 2014 Couchbase, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 		http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package snowball
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/blevesearch/bleve/v2/analysis"
+)
+
+func TestSnowballStemmer(t *testing.T) {
+
+	inputTokenStream := analysis.TokenStream{
+		&analysis.Token{
+			Term: []byte("walking"),
+		},
+		&analysis.Token{
+			Term: []byte("talked"),
+		},
+		&analysis.Token{
+			Term: []byte("business"),
+		},
+		&analysis.Token{
+			Term:    []byte("protected"),
+			KeyWord: true,
+		},
+		&analysis.Token{
+			Term: []byte("cat"),
+		},
+		&analysis.Token{
+			Term: []byte("done"),
+		},
+		// a term which does stem, but does not change length
+		&analysis.Token{
+			Term: []byte("marty"),
+		},
+	}
+
+	expectedTokenStream := analysis.TokenStream{
+		&analysis.Token{
+			Term: []byte("walk"),
+		},
+		&analysis.Token{
+			Term: []byte("talk"),
+		},
+		&analysis.Token{
+			Term: []byte("busi"),
+		},
+		&analysis.Token{
+			Term:    []byte("protected"),
+			KeyWord: true,
+		},
+		&analysis.Token{
+			Term: []byte("cat"),
+		},
+		&analysis.Token{
+			Term: []byte("done"),
+		},
+		&analysis.Token{
+			Term: []byte("marti"),
+		},
+	}
+
+	filter := NewSnowballStemmer("english")
+	ouputTokenStream := filter.Filter(inputTokenStream)
+	if !reflect.DeepEqual(ouputTokenStream, expectedTokenStream) {
+		t.Errorf("expected %#v got %#v", expectedTokenStream[3], ouputTokenStream[3])
+	}
+}
+
+func BenchmarkSnowballStemmer(b *testing.B) {
+
+	inputTokenStream := analysis.TokenStream{
+		&analysis.Token{
+			Term: []byte("walking"),
+		},
+		&analysis.Token{
+			Term: []byte("talked"),
+		},
+		&analysis.Token{
+			Term: []byte("business"),
+		},
+		&analysis.Token{
+			Term:    []byte("protected"),
+			KeyWord: true,
+		},
+		&analysis.Token{
+			Term: []byte("cat"),
+		},
+		&analysis.Token{
+			Term: []byte("done"),
+		},
+	}
+
+	filter := NewSnowballStemmer("english")
+	b.ResetTimer()
+
+	for i := 0; i < b.N; i++ {
+		filter.Filter(inputTokenStream)
+	}
+
+}