2014-07-11 20:49:59 +02:00
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// 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 search
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import (
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"fmt"
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)
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type ConstantScorer struct {
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constant float64
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boost float64
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explain bool
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queryNorm float64
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queryWeight float64
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queryWeightExplanation *Explanation
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}
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2014-07-30 18:30:38 +02:00
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func NewConstantScorer(constant float64, boost float64, explain bool) *ConstantScorer {
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rv := ConstantScorer{
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explain: explain,
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queryWeight: 1.0,
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constant: constant,
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2014-07-30 18:30:38 +02:00
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boost: boost,
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}
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return &rv
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}
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func (s *ConstantScorer) Weight() float64 {
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sum := s.boost
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return sum * sum
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}
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func (s *ConstantScorer) SetQueryNorm(qnorm float64) {
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s.queryNorm = qnorm
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// update the query weight
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s.queryWeight = s.boost * s.queryNorm
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if s.explain {
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childrenExplanations := make([]*Explanation, 2)
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childrenExplanations[0] = &Explanation{
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Value: s.boost,
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Message: "boost",
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}
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childrenExplanations[1] = &Explanation{
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Value: s.queryNorm,
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Message: "queryNorm",
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}
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s.queryWeightExplanation = &Explanation{
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Value: s.queryWeight,
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Message: fmt.Sprintf("ConstantScore()^%f, product of:", s.boost),
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Children: childrenExplanations,
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}
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}
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}
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func (s *ConstantScorer) Score(id string) *DocumentMatch {
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var scoreExplanation *Explanation
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score := s.constant
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if s.explain {
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scoreExplanation = &Explanation{
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Value: score,
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Message: fmt.Sprintf("ConstantScore()"),
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}
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}
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// if the query weight isn't 1, multiply
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if s.queryWeight != 1.0 {
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score = score * s.queryWeight
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if s.explain {
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childExplanations := make([]*Explanation, 2)
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childExplanations[0] = s.queryWeightExplanation
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childExplanations[1] = scoreExplanation
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scoreExplanation = &Explanation{
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Value: score,
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Message: fmt.Sprintf("weight(^%f), product of:", s.boost),
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Children: childExplanations,
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}
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}
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}
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rv := DocumentMatch{
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ID: id,
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Score: score,
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}
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if s.explain {
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rv.Expl = scoreExplanation
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}
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return &rv
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}
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