119 lines
2.8 KiB
Go
119 lines
2.8 KiB
Go
// Copyright (c) 2014 Couchbase, Inc.
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// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file
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// except in compliance with the License. You may obtain a copy of the License at
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// http://www.apache.org/licenses/LICENSE-2.0
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// Unless required by applicable law or agreed to in writing, software distributed under the
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// License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
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// either express or implied. See the License for the specific language governing permissions
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// and limitations under the License.
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package ngram_filter
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import (
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"bytes"
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"fmt"
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"unicode/utf8"
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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 = "ngram"
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type NgramFilter struct {
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minLength int
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maxLength int
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}
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func NewNgramFilter(minLength, maxLength int) *NgramFilter {
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return &NgramFilter{
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minLength: minLength,
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maxLength: maxLength,
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}
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}
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func (s *NgramFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
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rv := make(analysis.TokenStream, 0, len(input))
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for _, token := range input {
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runeCount := utf8.RuneCount(token.Term)
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runes := bytes.Runes(token.Term)
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for i := 0; i < runeCount; i++ {
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// index of the starting rune for this token
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for ngramSize := s.minLength; ngramSize <= s.maxLength; ngramSize++ {
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// build an ngram of this size starting at i
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if i+ngramSize <= runeCount {
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ngramTerm := buildTermFromRunes(runes[i : i+ngramSize])
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token := analysis.Token{
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Position: token.Position,
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Start: token.Start,
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End: token.End,
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Type: token.Type,
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Term: ngramTerm,
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}
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rv = append(rv, &token)
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}
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}
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}
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}
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return rv
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}
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func buildTermFromRunes(runes []rune) []byte {
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rv := make([]byte, 0, len(runes)*4)
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for _, r := range runes {
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runeBytes := make([]byte, utf8.RuneLen(r))
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utf8.EncodeRune(runeBytes, r)
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rv = append(rv, runeBytes...)
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}
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return rv
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}
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func NgramFilterConstructor(config map[string]interface{}, cache *registry.Cache) (analysis.TokenFilter, error) {
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minVal, ok := config["min"]
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if !ok {
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return nil, fmt.Errorf("must specify min")
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}
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min, err := convertToInt(minVal)
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if err != nil {
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return nil, err
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}
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maxVal, ok := config["max"]
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if !ok {
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return nil, fmt.Errorf("must specify max")
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}
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max, err := convertToInt(maxVal)
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if err != nil {
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return nil, err
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}
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return NewNgramFilter(min, max), nil
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}
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func init() {
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registry.RegisterTokenFilter(Name, NgramFilterConstructor)
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}
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// Expects either an int or a flaot64 value
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func convertToInt(val interface{}) (int, error) {
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var intVal int
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var floatVal float64
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var ok bool
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intVal, ok = val.(int)
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if ok {
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return intVal, nil
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}
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floatVal, ok = val.(float64)
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if ok {
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return int(floatVal), nil
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}
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return 0, fmt.Errorf("failed to convert to int value")
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}
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