forked from blevesearch/bleve
/
search_phrase.go
354 lines (310 loc) · 9.84 KB
/
search_phrase.go
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// 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 searcher
import (
"fmt"
"math"
"github.com/blevesearch/bleve/index"
"github.com/blevesearch/bleve/search"
)
type PhraseSearcher struct {
indexReader index.IndexReader
mustSearcher *ConjunctionSearcher
queryNorm float64
currMust *search.DocumentMatch
slop int
terms [][]string
initialized bool
}
func NewPhraseSearcher(indexReader index.IndexReader, terms []string, field string, options search.SearcherOptions) (*PhraseSearcher, error) {
// turn flat terms []string into [][]string
mterms := make([][]string, len(terms))
for i, term := range terms {
mterms[i] = []string{term}
}
return NewMultiPhraseSearcher(indexReader, mterms, field, options)
}
func NewMultiPhraseSearcher(indexReader index.IndexReader, terms [][]string, field string, options search.SearcherOptions) (*PhraseSearcher, error) {
options.IncludeTermVectors = true
var termPositionSearchers []search.Searcher
for _, termPos := range terms {
if len(termPos) == 1 && termPos[0] != "" {
// single term
ts, err := NewTermSearcher(indexReader, termPos[0], field, 1.0, options)
if err != nil {
// close any searchers already opened
for _, ts := range termPositionSearchers {
_ = ts.Close()
}
return nil, fmt.Errorf("phrase searcher error building term searcher: %v", err)
}
termPositionSearchers = append(termPositionSearchers, ts)
} else if len(termPos) > 1 {
// multiple terms
var termSearchers []search.Searcher
for _, term := range termPos {
if term == "" {
continue
}
ts, err := NewTermSearcher(indexReader, term, field, 1.0, options)
if err != nil {
// close any searchers already opened
for _, ts := range termPositionSearchers {
_ = ts.Close()
}
return nil, fmt.Errorf("phrase searcher error building term searcher: %v", err)
}
termSearchers = append(termSearchers, ts)
}
disjunction, err := NewDisjunctionSearcher(indexReader, termSearchers, 1, options)
if err != nil {
// close any searchers already opened
for _, ts := range termPositionSearchers {
_ = ts.Close()
}
return nil, fmt.Errorf("phrase searcher error building term position disjunction searcher: %v", err)
}
termPositionSearchers = append(termPositionSearchers, disjunction)
}
}
mustSearcher, err := NewConjunctionSearcher(indexReader, termPositionSearchers, options)
if err != nil {
// close any searchers already opened
for _, ts := range termPositionSearchers {
_ = ts.Close()
}
return nil, fmt.Errorf("phrase searcher error building conjunction searcher: %v", err)
}
// build our searcher
rv := PhraseSearcher{
indexReader: indexReader,
mustSearcher: mustSearcher,
terms: terms,
}
rv.computeQueryNorm()
return &rv, nil
}
func (s *PhraseSearcher) computeQueryNorm() {
// first calculate sum of squared weights
sumOfSquaredWeights := 0.0
if s.mustSearcher != nil {
sumOfSquaredWeights += s.mustSearcher.Weight()
}
// now compute query norm from this
s.queryNorm = 1.0 / math.Sqrt(sumOfSquaredWeights)
// finally tell all the downstream searchers the norm
if s.mustSearcher != nil {
s.mustSearcher.SetQueryNorm(s.queryNorm)
}
}
func (s *PhraseSearcher) initSearchers(ctx *search.SearchContext) error {
err := s.advanceNextMust(ctx)
if err != nil {
return err
}
s.initialized = true
return nil
}
func (s *PhraseSearcher) advanceNextMust(ctx *search.SearchContext) error {
var err error
if s.mustSearcher != nil {
s.currMust, err = s.mustSearcher.Next(ctx)
if err != nil {
return err
}
}
return nil
}
func (s *PhraseSearcher) Weight() float64 {
return s.mustSearcher.Weight()
}
func (s *PhraseSearcher) SetQueryNorm(qnorm float64) {
s.mustSearcher.SetQueryNorm(qnorm)
}
func (s *PhraseSearcher) Next(ctx *search.SearchContext) (*search.DocumentMatch, error) {
if !s.initialized {
err := s.initSearchers(ctx)
if err != nil {
return nil, err
}
}
for s.currMust != nil {
// check this match against phrase constraints
rv := s.checkCurrMustMatch(ctx)
// prepare for next iteration (either loop or subsequent call to Next())
err := s.advanceNextMust(ctx)
if err != nil {
return nil, err
}
// if match satisfied phrase constraints return it as a hit
if rv != nil {
return rv, nil
}
}
return nil, nil
}
// checkCurrMustMatch is soley concerned with determining if the DocumentMatch
// pointed to by s.currMust (which satisifies the pre-condition searcher)
// also satisfies the phase constraints. if so, it returns a DocumentMatch
// for this document, otherwise nil
func (s *PhraseSearcher) checkCurrMustMatch(ctx *search.SearchContext) *search.DocumentMatch {
rvftlm := make(search.FieldTermLocationMap, 0)
freq := 0
// typically we would expect there to only actually be results in
// one field, but we allow for this to not be the case
// but, we note that phrase constraints can only be satisfied within
// a single field, so we can check them each independently
for field, tlm := range s.currMust.Locations {
f, rvtlm := s.checkCurrMustMatchField(ctx, tlm)
if f > 0 {
freq += f
rvftlm[field] = rvtlm
}
}
if freq > 0 {
// return match
rv := s.currMust
rv.Locations = rvftlm
return rv
}
return nil
}
// checkCurrMustMatchField is soley concerned with determining if one particular
// field within the currMust DocumentMatch Locations satisfies the phase
// constraints (possibly more than once). if so, the number of times it was
// satisfied, and these locations are returned. otherwise 0 and either
// a nil or empty TermLocationMap
func (s *PhraseSearcher) checkCurrMustMatchField(ctx *search.SearchContext, tlm search.TermLocationMap) (int, search.TermLocationMap) {
paths := findPhrasePaths(0, nil, s.terms, tlm, nil, 0)
rv := make(search.TermLocationMap, len(s.terms))
for _, p := range paths {
p.MergeInto(rv)
}
return len(paths), rv
}
type phrasePart struct {
term string
loc *search.Location
}
func (p *phrasePart) String() string {
return fmt.Sprintf("[%s %v]", p.term, p.loc)
}
type phrasePath []*phrasePart
func (p phrasePath) MergeInto(in search.TermLocationMap) {
for _, pp := range p {
in[pp.term] = append(in[pp.term], pp.loc)
}
}
// findPhrasePaths is a function to identify phase matches from a set of known
// term locations. the implementation is recursive, so care must be taken
// with arguments and return values.
//
// prev - the previous location, nil on first invocation
// phraseTerms - slice containing the phrase terms themselves
// may contain empty string as placeholder (don't care)
// tlm - the Term Location Map containing all relevant term locations
// offset - the offset from the previous that this next term must match
// p - the current path being explored (appended to in recursive calls)
// this is the primary state being built during the traversal
//
// returns slice of paths, or nil if invocation did not find any successul paths
func findPhrasePaths(prevPos uint64, ap search.ArrayPositions, phraseTerms [][]string, tlm search.TermLocationMap, p phrasePath, remainingSlop int) []phrasePath {
// no more terms
if len(phraseTerms) < 1 {
return []phrasePath{p}
}
car := phraseTerms[0]
cdr := phraseTerms[1:]
// empty term is treated as match (continue)
if len(car) == 0 || (len(car) == 1 && car[0] == "") {
nextPos := prevPos + 1
if prevPos == 0 {
// if prevPos was 0, don't set it to 1 (as thats not a real abs pos)
nextPos = 0 // don't advance nextPos if prevPos was 0
}
return findPhrasePaths(nextPos, ap, cdr, tlm, p, remainingSlop)
}
var rv []phrasePath
// locations for this term
for _, carTerm := range car {
locations := tlm[carTerm]
for _, loc := range locations {
if prevPos != 0 && !loc.ArrayPositions.Equals(ap) {
// if the array positions are wrong, can't match, try next location
continue
}
// compute distance from previous phrase term
dist := 0
if prevPos != 0 {
dist = editDistance(prevPos+1, loc.Pos)
}
// if enough slop reamining, continue recursively
if prevPos == 0 || (remainingSlop-dist) >= 0 {
// this location works, add it to the path (but not for empty term)
px := append(p, &phrasePart{term: carTerm, loc: loc})
rv = append(rv, findPhrasePaths(loc.Pos, loc.ArrayPositions, cdr, tlm, px, remainingSlop-dist)...)
}
}
}
return rv
}
func editDistance(p1, p2 uint64) int {
dist := int(p1 - p2)
if dist < 0 {
return -dist
}
return dist
}
func (s *PhraseSearcher) Advance(ctx *search.SearchContext, ID index.IndexInternalID) (*search.DocumentMatch, error) {
if !s.initialized {
err := s.initSearchers(ctx)
if err != nil {
return nil, err
}
}
if s.currMust != nil {
if s.currMust.IndexInternalID.Compare(ID) >= 0 {
return s.Next(ctx)
}
ctx.DocumentMatchPool.Put(s.currMust)
}
if s.currMust == nil {
return nil, nil
}
var err error
s.currMust, err = s.mustSearcher.Advance(ctx, ID)
if err != nil {
return nil, err
}
return s.Next(ctx)
}
func (s *PhraseSearcher) Count() uint64 {
// for now return a worst case
return s.mustSearcher.Count()
}
func (s *PhraseSearcher) Close() error {
if s.mustSearcher != nil {
err := s.mustSearcher.Close()
if err != nil {
return err
}
}
return nil
}
func (s *PhraseSearcher) Min() int {
return 0
}
func (s *PhraseSearcher) DocumentMatchPoolSize() int {
return s.mustSearcher.DocumentMatchPoolSize() + 1
}