60efecc8e9
the collector has optimizations to avoid allocation and reslicing during the common case of searching for top hits however, in some cases users request an a very large number of search hits to be returned (attempting to get them all) this caused unnecessary allocation of ram. to address this we introduce a new constant PreAllocSizeSkipCap it defaults the value of 1000. if your search+skip is less than this constant, you get the optimized behavior. if your search+skip is greater than this, we cap the preallcations to this lower value. additional space is acquired on an as needed basis by growing the DocumentMatchPool and reslicing the collector backing slice applications can change the value of PreAllocSizeSkipCap to suit their own needs fixes #408
265 lines
7.3 KiB
Go
265 lines
7.3 KiB
Go
// 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 collectors
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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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const 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.FinalizeDocID(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 comparision, 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.FinalizeDocID(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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