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269 lines
7.3 KiB
269 lines
7.3 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 collector
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import (
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"time"
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"github.com/blevesearch/bleve/index"
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"github.com/blevesearch/bleve/search"
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"golang.org/x/net/context"
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)
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// PreAllocSizeSkipCap will cap preallocation to this amount when
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// size+skip exceeds this value
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var PreAllocSizeSkipCap = 1000
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type collectorCompare func(i, j *search.DocumentMatch) int
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type collectorFixup func(d *search.DocumentMatch) error
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// TopNCollector collects the top N hits, optionally skipping some results
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type TopNCollector struct {
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size int
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skip int
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total uint64
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maxScore float64
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took time.Duration
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sort search.SortOrder
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results search.DocumentMatchCollection
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facetsBuilder *search.FacetsBuilder
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store *collectStoreSlice
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needDocIds bool
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neededFields []string
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cachedScoring []bool
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cachedDesc []bool
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lowestMatchOutsideResults *search.DocumentMatch
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}
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// CheckDoneEvery controls how frequently we check the context deadline
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const CheckDoneEvery = uint64(1024)
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// NewTopNCollector builds a collector to find the top 'size' hits
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// skipping over the first 'skip' hits
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// ordering hits by the provided sort order
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func NewTopNCollector(size int, skip int, sort search.SortOrder) *TopNCollector {
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hc := &TopNCollector{size: size, skip: skip, sort: sort}
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// pre-allocate space on the store to avoid reslicing
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// unless the size + skip is too large, then cap it
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// everything should still work, just reslices as necessary
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backingSize := size + skip + 1
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if size+skip > PreAllocSizeSkipCap {
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backingSize = PreAllocSizeSkipCap + 1
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}
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hc.store = newStoreSlice(backingSize, func(i, j *search.DocumentMatch) int {
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return hc.sort.Compare(hc.cachedScoring, hc.cachedDesc, i, j)
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})
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// these lookups traverse an interface, so do once up-front
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if sort.RequiresDocID() {
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hc.needDocIds = true
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}
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hc.neededFields = sort.RequiredFields()
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hc.cachedScoring = sort.CacheIsScore()
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hc.cachedDesc = sort.CacheDescending()
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return hc
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}
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// Collect goes to the index to find the matching documents
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func (hc *TopNCollector) Collect(ctx context.Context, searcher search.Searcher, reader index.IndexReader) error {
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startTime := time.Now()
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var err error
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var next *search.DocumentMatch
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// pre-allocate enough space in the DocumentMatchPool
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// unless the size + skip is too large, then cap it
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// everything should still work, just allocates DocumentMatches on demand
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backingSize := hc.size + hc.skip + 1
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if hc.size+hc.skip > PreAllocSizeSkipCap {
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backingSize = PreAllocSizeSkipCap + 1
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}
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searchContext := &search.SearchContext{
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DocumentMatchPool: search.NewDocumentMatchPool(backingSize+searcher.DocumentMatchPoolSize(), len(hc.sort)),
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}
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select {
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case <-ctx.Done():
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return ctx.Err()
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default:
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next, err = searcher.Next(searchContext)
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}
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for err == nil && next != nil {
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if hc.total%CheckDoneEvery == 0 {
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select {
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case <-ctx.Done():
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return ctx.Err()
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default:
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}
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}
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if hc.facetsBuilder != nil {
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err = hc.facetsBuilder.Update(next)
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if err != nil {
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break
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}
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}
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err = hc.collectSingle(searchContext, reader, next)
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if err != nil {
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break
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}
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next, err = searcher.Next(searchContext)
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}
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// compute search duration
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hc.took = time.Since(startTime)
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if err != nil {
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return err
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}
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// finalize actual results
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err = hc.finalizeResults(reader)
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if err != nil {
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return err
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}
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return nil
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}
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var sortByScoreOpt = []string{"_score"}
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func (hc *TopNCollector) collectSingle(ctx *search.SearchContext, reader index.IndexReader, d *search.DocumentMatch) error {
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// increment total hits
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hc.total++
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d.HitNumber = hc.total
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// update max score
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if d.Score > hc.maxScore {
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hc.maxScore = d.Score
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}
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var err error
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// see if we need to load ID (at this early stage, for example to sort on it)
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if hc.needDocIds {
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d.ID, err = reader.ExternalID(d.IndexInternalID)
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if err != nil {
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return err
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}
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}
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// see if we need to load the stored fields
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if len(hc.neededFields) > 0 {
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// find out which fields haven't been loaded yet
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fieldsToLoad := d.CachedFieldTerms.FieldsNotYetCached(hc.neededFields)
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// look them up
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fieldTerms, err := reader.DocumentFieldTerms(d.IndexInternalID, fieldsToLoad)
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if err != nil {
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return err
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}
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// cache these as well
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if d.CachedFieldTerms == nil {
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d.CachedFieldTerms = make(map[string][]string)
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}
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d.CachedFieldTerms.Merge(fieldTerms)
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}
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// compute this hits sort value
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if len(hc.sort) == 1 && hc.cachedScoring[0] {
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d.Sort = sortByScoreOpt
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} else {
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hc.sort.Value(d)
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}
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// optimization, we track lowest sorting hit already removed from heap
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// with this one comparison, we can avoid all heap operations if
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// this hit would have been added and then immediately removed
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if hc.lowestMatchOutsideResults != nil {
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cmp := hc.sort.Compare(hc.cachedScoring, hc.cachedDesc, d, hc.lowestMatchOutsideResults)
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if cmp >= 0 {
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// this hit can't possibly be in the result set, so avoid heap ops
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ctx.DocumentMatchPool.Put(d)
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return nil
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}
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}
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hc.store.Add(d)
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if hc.store.Len() > hc.size+hc.skip {
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removed := hc.store.RemoveLast()
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if hc.lowestMatchOutsideResults == nil {
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hc.lowestMatchOutsideResults = removed
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} else {
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cmp := hc.sort.Compare(hc.cachedScoring, hc.cachedDesc, removed, hc.lowestMatchOutsideResults)
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if cmp < 0 {
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tmp := hc.lowestMatchOutsideResults
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hc.lowestMatchOutsideResults = removed
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ctx.DocumentMatchPool.Put(tmp)
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}
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}
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}
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return nil
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}
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// SetFacetsBuilder registers a facet builder for this collector
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func (hc *TopNCollector) SetFacetsBuilder(facetsBuilder *search.FacetsBuilder) {
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hc.facetsBuilder = facetsBuilder
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}
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// finalizeResults starts with the heap containing the final top size+skip
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// it now throws away the results to be skipped
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// and does final doc id lookup (if necessary)
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func (hc *TopNCollector) finalizeResults(r index.IndexReader) error {
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var err error
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hc.results, err = hc.store.Final(hc.skip, func(doc *search.DocumentMatch) error {
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if doc.ID == "" {
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// look up the id since we need it for lookup
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var err error
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doc.ID, err = r.ExternalID(doc.IndexInternalID)
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if err != nil {
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return err
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}
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}
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return nil
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})
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return err
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}
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// Results returns the collected hits
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func (hc *TopNCollector) Results() search.DocumentMatchCollection {
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return hc.results
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}
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// Total returns the total number of hits
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func (hc *TopNCollector) Total() uint64 {
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return hc.total
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}
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// MaxScore returns the maximum score seen across all the hits
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func (hc *TopNCollector) MaxScore() float64 {
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return hc.maxScore
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}
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// Took returns the time spent collecting hits
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func (hc *TopNCollector) Took() time.Duration {
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return hc.took
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}
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// FacetResults returns the computed facets results
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func (hc *TopNCollector) FacetResults() search.FacetResults {
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if hc.facetsBuilder != nil {
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return hc.facetsBuilder.Results()
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}
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return search.FacetResults{}
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}
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