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118 lines
3.1 KiB
118 lines
3.1 KiB
// Copyright (c) 2014 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 searcher
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import (
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"fmt"
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"github.com/blevesearch/bleve/index"
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"github.com/blevesearch/bleve/search"
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)
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var MaxFuzziness = 2
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func NewFuzzySearcher(indexReader index.IndexReader, term string,
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prefix, fuzziness int, field string, boost float64,
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options search.SearcherOptions) (search.Searcher, error) {
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if fuzziness > MaxFuzziness {
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return nil, fmt.Errorf("fuzziness exceeds max (%d)", MaxFuzziness)
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}
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if fuzziness < 0 {
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return nil, fmt.Errorf("invalid fuzziness, negative")
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}
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// Note: we don't byte slice the term for a prefix because of runes.
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prefixTerm := ""
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for i, r := range term {
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if i < prefix {
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prefixTerm += string(r)
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} else {
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break
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}
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}
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candidateTerms, err := findFuzzyCandidateTerms(indexReader, term, fuzziness,
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field, prefixTerm)
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if err != nil {
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return nil, err
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}
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return NewMultiTermSearcher(indexReader, candidateTerms, field,
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boost, options, true)
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}
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func findFuzzyCandidateTerms(indexReader index.IndexReader, term string,
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fuzziness int, field, prefixTerm string) (rv []string, err error) {
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rv = make([]string, 0)
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// in case of advanced reader implementations directly call
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// the levenshtein automaton based iterator to collect the
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// candidate terms
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if ir, ok := indexReader.(index.IndexReaderFuzzy); ok {
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fieldDict, err := ir.FieldDictFuzzy(field, term, fuzziness, prefixTerm)
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if err != nil {
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return nil, err
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}
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defer func() {
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if cerr := fieldDict.Close(); cerr != nil && err == nil {
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err = cerr
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}
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}()
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tfd, err := fieldDict.Next()
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for err == nil && tfd != nil {
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rv = append(rv, tfd.Term)
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if tooManyClauses(len(rv)) {
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return nil, tooManyClausesErr(field, len(rv))
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}
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tfd, err = fieldDict.Next()
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}
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return rv, err
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}
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var fieldDict index.FieldDict
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if len(prefixTerm) > 0 {
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fieldDict, err = indexReader.FieldDictPrefix(field, []byte(prefixTerm))
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} else {
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fieldDict, err = indexReader.FieldDict(field)
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}
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if err != nil {
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return nil, err
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}
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defer func() {
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if cerr := fieldDict.Close(); cerr != nil && err == nil {
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err = cerr
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}
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}()
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// enumerate terms and check levenshtein distance
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var reuse []int
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tfd, err := fieldDict.Next()
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for err == nil && tfd != nil {
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var ld int
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var exceeded bool
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ld, exceeded, reuse = search.LevenshteinDistanceMaxReuseSlice(term, tfd.Term, fuzziness, reuse)
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if !exceeded && ld <= fuzziness {
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rv = append(rv, tfd.Term)
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if tooManyClauses(len(rv)) {
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return nil, tooManyClausesErr(field, len(rv))
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}
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}
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tfd, err = fieldDict.Next()
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}
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return rv, err
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}
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