forked from blevesearch/bleve
/
unique.go
53 lines (45 loc) · 1.55 KB
/
unique.go
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// Copyright (c) 2018 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 unique
import (
"github.com/blevesearch/bleve/analysis"
"github.com/blevesearch/bleve/registry"
)
const Name = "unique"
// UniqueTermFilter retains only the tokens which mark the first occurrence of
// a term. Tokens whose term appears in a preceding token are dropped.
type UniqueTermFilter struct{}
func NewUniqueTermFilter() *UniqueTermFilter {
return &UniqueTermFilter{}
}
func (f *UniqueTermFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
encounteredTerms := make(map[string]struct{}, len(input)/4)
j := 0
for _, token := range input {
term := string(token.Term)
if _, ok := encounteredTerms[term]; ok {
continue
}
encounteredTerms[term] = struct{}{}
input[j] = token
j++
}
return input[:j]
}
func UniqueTermFilterConstructor(config map[string]interface{}, cache *registry.Cache) (analysis.TokenFilter, error) {
return NewUniqueTermFilter(), nil
}
func init() {
registry.RegisterTokenFilter(Name, UniqueTermFilterConstructor)
}