initial impl of fuzzy search

query.go

@@ -35,6 +35,18 @@ func ParseQuery(input []byte) (Query, error) {
 	if err != nil {
 		return nil, err
 	}
+	_, hasFuzziness := tmp["fuzziness"]
+	if hasFuzziness {
+		var rv fuzzyQuery
+		err := json.Unmarshal(input, &rv)
+		if err != nil {
+			return nil, err
+		}
+		if rv.Boost() == 0 {
+			rv.SetBoost(1)
+		}
+		return &rv, nil
+	}
 	_, isTermQuery := tmp["term"]
 	if isTermQuery {
 		var rv termQuery

query_fuzzy.go

@@ -0,0 +1,66 @@
+//  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 bleve
+
+import (
+	"github.com/blevesearch/bleve/index"
+	"github.com/blevesearch/bleve/search"
+	"github.com/blevesearch/bleve/search/searchers"
+)
+
+type fuzzyQuery struct {
+	Term      string  `json:"term"`
+	Prefix    int     `json:"prefix_length"`
+	Fuzziness int     `json:"fuzziness"`
+	FieldVal  string  `json:"field,omitempty"`
+	BoostVal  float64 `json:"boost,omitempty"`
+}
+
+// NewPrefixQuery creates a new Query which finds
+// documents containing terms that start with the
+// specified prefix.
+func NewFuzzyQuery(term string) *fuzzyQuery {
+	return &fuzzyQuery{
+		Term:      term,
+		Prefix:    0,
+		Fuzziness: 1,
+		BoostVal:  1.0,
+	}
+}
+
+func (q *fuzzyQuery) Boost() float64 {
+	return q.BoostVal
+}
+
+func (q *fuzzyQuery) SetBoost(b float64) Query {
+	q.BoostVal = b
+	return q
+}
+
+func (q *fuzzyQuery) Field() string {
+	return q.FieldVal
+}
+
+func (q *fuzzyQuery) SetField(f string) Query {
+	q.FieldVal = f
+	return q
+}
+
+func (q *fuzzyQuery) Searcher(i index.IndexReader, m *IndexMapping, explain bool) (search.Searcher, error) {
+	field := q.FieldVal
+	if q.FieldVal == "" {
+		field = m.DefaultField
+	}
+	return searchers.NewFuzzySearcher(i, q.Term, q.Prefix, q.Fuzziness, field, q.BoostVal, explain)
+}
+
+func (q *fuzzyQuery) Validate() error {
+	return nil
+}

search/searchers/search_fuzzy.go

@@ -0,0 +1,136 @@
+//  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 searchers
+
+import (
+	"github.com/blevesearch/bleve/index"
+	"github.com/blevesearch/bleve/search"
+)
+
+type FuzzySearcher struct {
+	indexReader index.IndexReader
+	term        string
+	prefix      int
+	fuzziness   int
+	field       string
+	explain     bool
+	searcher    *DisjunctionSearcher
+}
+
+func NewFuzzySearcher(indexReader index.IndexReader, term string, prefix, fuzziness int, field string, boost float64, explain bool) (*FuzzySearcher, error) {
+	prefixTerm := ""
+	for i, r := range term {
+		if i < prefix {
+			prefixTerm += string(r)
+		}
+	}
+
+	// find the terms with this prefix
+	fieldReader, err := indexReader.FieldReader(field, []byte(prefixTerm), []byte(prefixTerm))
+
+	// enumerate terms and check levenshtein distance
+	candidateTerms := make([]string, 0)
+	tfd, err := fieldReader.Next()
+	for err == nil && tfd != nil {
+		ld := levenshteinDistance(&term, &tfd.Term)
+		if ld <= fuzziness {
+			candidateTerms = append(candidateTerms, tfd.Term)
+		}
+		tfd, err = fieldReader.Next()
+	}
+
+	// enumerate all the terms in the range
+	qsearchers := make([]search.Searcher, 0, 25)
+
+	for _, cterm := range candidateTerms {
+		qsearcher, err := NewTermSearcher(indexReader, cterm, field, 1.0, explain)
+		if err != nil {
+			return nil, err
+		}
+		qsearchers = append(qsearchers, qsearcher)
+	}
+
+	// build disjunction searcher of these ranges
+	searcher, err := NewDisjunctionSearcher(indexReader, qsearchers, 0, explain)
+	if err != nil {
+		return nil, err
+	}
+
+	return &FuzzySearcher{
+		indexReader: indexReader,
+		term:        term,
+		prefix:      prefix,
+		fuzziness:   fuzziness,
+		field:       field,
+		explain:     explain,
+		searcher:    searcher,
+	}, nil
+}
+func (s *FuzzySearcher) Count() uint64 {
+	return s.searcher.Count()
+}
+
+func (s *FuzzySearcher) Weight() float64 {
+	return s.searcher.Weight()
+}
+
+func (s *FuzzySearcher) SetQueryNorm(qnorm float64) {
+	s.searcher.SetQueryNorm(qnorm)
+}
+
+func (s *FuzzySearcher) Next() (*search.DocumentMatch, error) {
+	return s.searcher.Next()
+
+}
+
+func (s *FuzzySearcher) Advance(ID string) (*search.DocumentMatch, error) {
+	return s.searcher.Next()
+}
+
+func (s *FuzzySearcher) Close() {
+	s.searcher.Close()
+}
+
+func (s *FuzzySearcher) Min() int {
+	return 0
+}
+
+func levenshteinDistance(a, b *string) int {
+	la := len(*a)
+	lb := len(*b)
+	d := make([]int, la+1)
+	var lastdiag, olddiag, temp int
+
+	for i := 1; i <= la; i++ {
+		d[i] = i
+	}
+	for i := 1; i <= lb; i++ {
+		d[0] = i
+		lastdiag = i - 1
+		for j := 1; j <= la; j++ {
+			olddiag = d[j]
+			min := d[j] + 1
+			if (d[j-1] + 1) < min {
+				min = d[j-1] + 1
+			}
+			if (*a)[j-1] == (*b)[i-1] {
+				temp = 0
+			} else {
+				temp = 1
+			}
+			if (lastdiag + temp) < min {
+				min = lastdiag + temp
+			}
+			d[j] = min
+			lastdiag = olddiag
+		}
+	}
+	return d[la]
+}