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53 lines
1.5 KiB
53 lines
1.5 KiB
// Copyright (c) 2018 Couchbase, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package unique
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import (
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"github.com/blevesearch/bleve/analysis"
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"github.com/blevesearch/bleve/registry"
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)
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const Name = "unique"
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// UniqueTermFilter retains only the tokens which mark the first occurence of
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// a term. Tokens whose term appears in a preceding token are dropped.
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type UniqueTermFilter struct{}
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func NewUniqueTermFilter() *UniqueTermFilter {
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return &UniqueTermFilter{}
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}
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func (f *UniqueTermFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
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encounteredTerms := make(map[string]struct{}, len(input)/4)
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j := 0
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for _, token := range input {
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term := string(token.Term)
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if _, ok := encounteredTerms[term]; ok {
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continue
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}
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encounteredTerms[term] = struct{}{}
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input[j] = token
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j++
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}
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return input[:j]
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}
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func UniqueTermFilterConstructor(config map[string]interface{}, cache *registry.Cache) (analysis.TokenFilter, error) {
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return NewUniqueTermFilter(), nil
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}
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func init() {
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registry.RegisterTokenFilter(Name, UniqueTermFilterConstructor)
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}
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