query_match_phrase.go

//  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 (
	"fmt"

	"github.com/blevesearch/bleve/analysis"
	"github.com/blevesearch/bleve/index"
	"github.com/blevesearch/bleve/search"
)

type matchPhraseQuery struct {
	MatchPhrase string  `json:"match_phrase"`
	FieldVal    string  `json:"field,omitempty"`
	Analyzer    string  `json:"analyzer,omitempty"`
	BoostVal    float64 `json:"boost,omitempty"`
}

// NewMatchPhraseQuery creates a new Query object
// for matching phrases in the index.
// An Analyzer is chosen based on the field.
// Input text is analyzed using this analyzer.
// Token terms resulting from this analysis are
// used to build a search phrase.  Result documents
// must match this phrase.
func NewMatchPhraseQuery(matchPhrase string) *matchPhraseQuery {
	return &matchPhraseQuery{
		MatchPhrase: matchPhrase,
		BoostVal:    1.0,
	}
}

func (q *matchPhraseQuery) Boost() float64 {
	return q.BoostVal
}

func (q *matchPhraseQuery) SetBoost(b float64) Query {
	q.BoostVal = b
	return q
}

func (q *matchPhraseQuery) Field() string {
	return q.FieldVal
}

func (q *matchPhraseQuery) SetField(f string) Query {
	q.FieldVal = f
	return q
}

func (q *matchPhraseQuery) Searcher(i index.IndexReader, m *IndexMapping, explain bool) (search.Searcher, error) {
	field := q.FieldVal
	if q.FieldVal == "" {
		field = m.DefaultField
	}

	analyzerName := ""
	if q.Analyzer != "" {
		analyzerName = q.Analyzer
	} else {
		analyzerName = m.analyzerNameForPath(field)
	}
	analyzer := m.analyzerNamed(analyzerName)
	if analyzer == nil {
		return nil, fmt.Errorf("no analyzer named '%s' registered", q.Analyzer)
	}

	tokens := analyzer.Analyze([]byte(q.MatchPhrase))
	if len(tokens) > 0 {
		phrase := tokenStreamToPhrase(tokens)
		phraseQuery := NewPhraseQuery(phrase, field).SetBoost(q.BoostVal)
		return phraseQuery.Searcher(i, m, explain)
	}
	noneQuery := NewMatchNoneQuery()
	return noneQuery.Searcher(i, m, explain)
}

func tokenStreamToPhrase(tokens analysis.TokenStream) []string {
	firstPosition := int(^uint(0) >> 1)
	lastPosition := 0
	for _, token := range tokens {
		if token.Position < firstPosition {
			firstPosition = token.Position
		}
		if token.Position > lastPosition {
			lastPosition = token.Position
		}
	}
	phraseLen := lastPosition - firstPosition + 1
	if phraseLen > 0 {
		rv := make([]string, phraseLen)
		for i := 0; i < phraseLen; i++ {
			rv[i] = ""
		}
		for _, token := range tokens {
			pos := token.Position - firstPosition
			rv[pos] = string(token.Term)
		}
		return rv
	}
	return nil
}

func (q *matchPhraseQuery) Validate() error {
	return nil
}