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optimize.go
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optimize.go
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// Copyright (c) 2018 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 scorch
import (
"fmt"
"github.com/RoaringBitmap/roaring"
"github.com/blevesearch/bleve/index"
"github.com/blevesearch/bleve/index/scorch/segment"
"github.com/blevesearch/bleve/index/scorch/segment/zap"
)
var OptimizeConjunction = true
var OptimizeConjunctionUnadorned = true
var OptimizeDisjunctionUnadorned = true
func (s *IndexSnapshotTermFieldReader) Optimize(kind string,
octx index.OptimizableContext) (index.OptimizableContext, error) {
if OptimizeConjunction && kind == "conjunction" {
return s.optimizeConjunction(octx)
}
if OptimizeConjunctionUnadorned && kind == "conjunction:unadorned" {
return s.optimizeConjunctionUnadorned(octx)
}
if OptimizeDisjunctionUnadorned && kind == "disjunction:unadorned" {
return s.optimizeDisjunctionUnadorned(octx)
}
return octx, nil
}
var OptimizeDisjunctionUnadornedMinChildCardinality = uint64(256)
// ----------------------------------------------------------------
func (s *IndexSnapshotTermFieldReader) optimizeConjunction(
octx index.OptimizableContext) (index.OptimizableContext, error) {
if octx == nil {
octx = &OptimizeTFRConjunction{snapshot: s.snapshot}
}
o, ok := octx.(*OptimizeTFRConjunction)
if !ok {
return octx, nil
}
if o.snapshot != s.snapshot {
return nil, fmt.Errorf("tried to optimize conjunction across different snapshots")
}
o.tfrs = append(o.tfrs, s)
return o, nil
}
type OptimizeTFRConjunction struct {
snapshot *IndexSnapshot
tfrs []*IndexSnapshotTermFieldReader
}
func (o *OptimizeTFRConjunction) Finish() (index.Optimized, error) {
if len(o.tfrs) <= 1 {
return nil, nil
}
for i := range o.snapshot.segment {
itr0, ok := o.tfrs[0].iterators[i].(*zap.PostingsIterator)
if !ok || itr0.ActualBM == nil {
continue
}
itr1, ok := o.tfrs[1].iterators[i].(*zap.PostingsIterator)
if !ok || itr1.ActualBM == nil {
continue
}
bm := roaring.And(itr0.ActualBM, itr1.ActualBM)
for _, tfr := range o.tfrs[2:] {
itr, ok := tfr.iterators[i].(*zap.PostingsIterator)
if !ok || itr.ActualBM == nil {
continue
}
bm.And(itr.ActualBM)
}
// in this conjunction optimization, the postings iterators
// will all share the same AND'ed together actual bitmap. The
// regular conjunction searcher machinery will still be used,
// but the underlying bitmap will be smaller.
for _, tfr := range o.tfrs {
itr, ok := tfr.iterators[i].(*zap.PostingsIterator)
if ok && itr.ActualBM != nil {
itr.ActualBM = bm
itr.Actual = bm.Iterator()
}
}
}
return nil, nil
}
// ----------------------------------------------------------------
// An "unadorned" conjunction optimization is appropriate when
// additional or subsidiary information like freq-norm's and
// term-vectors are not required, and instead only the internal-id's
// are needed.
func (s *IndexSnapshotTermFieldReader) optimizeConjunctionUnadorned(
octx index.OptimizableContext) (index.OptimizableContext, error) {
if octx == nil {
octx = &OptimizeTFRConjunctionUnadorned{snapshot: s.snapshot}
}
o, ok := octx.(*OptimizeTFRConjunctionUnadorned)
if !ok {
return nil, nil
}
if o.snapshot != s.snapshot {
return nil, fmt.Errorf("tried to optimize unadorned conjunction across different snapshots")
}
o.tfrs = append(o.tfrs, s)
return o, nil
}
type OptimizeTFRConjunctionUnadorned struct {
snapshot *IndexSnapshot
tfrs []*IndexSnapshotTermFieldReader
}
var OptimizeTFRConjunctionUnadornedTerm = []byte("<conjunction:unadorned>")
var OptimizeTFRConjunctionUnadornedField = "*"
// Finish of an unadorned conjunction optimization will compute a
// termFieldReader with an "actual" bitmap that represents the
// constituent bitmaps AND'ed together. This termFieldReader cannot
// provide any freq-norm or termVector associated information.
func (o *OptimizeTFRConjunctionUnadorned) Finish() (rv index.Optimized, err error) {
if len(o.tfrs) <= 1 {
return nil, nil
}
// We use an artificial term and field because the optimized
// termFieldReader can represent multiple terms and fields.
oTFR := &IndexSnapshotTermFieldReader{
term: OptimizeTFRConjunctionUnadornedTerm,
field: OptimizeTFRConjunctionUnadornedField,
snapshot: o.snapshot,
iterators: make([]segment.PostingsIterator, len(o.snapshot.segment)),
segmentOffset: 0,
includeFreq: false,
includeNorm: false,
includeTermVectors: false,
}
var actualBMs []*roaring.Bitmap // Collected from regular posting lists.
OUTER:
for i := range o.snapshot.segment {
actualBMs = actualBMs[:0]
var docNum1HitLast uint64
var docNum1HitLastOk bool
for _, tfr := range o.tfrs {
if _, ok := tfr.iterators[i].(*segment.EmptyPostingsIterator); ok {
// An empty postings iterator means the entire AND is empty.
oTFR.iterators[i] = segment.AnEmptyPostingsIterator
continue OUTER
}
itr, ok := tfr.iterators[i].(*zap.PostingsIterator)
if !ok {
// We optimize zap postings iterators only.
return nil, nil
}
// If the postings iterator is "1-hit" optimized, then we
// can perform several optimizations up-front here.
docNum1Hit, ok := itr.DocNum1Hit()
if ok {
if docNum1Hit == zap.DocNum1HitFinished {
// An empty docNum here means the entire AND is empty.
oTFR.iterators[i] = segment.AnEmptyPostingsIterator
continue OUTER
}
if docNum1HitLastOk && docNum1HitLast != docNum1Hit {
// The docNum1Hit doesn't match the previous
// docNum1HitLast, so the entire AND is empty.
oTFR.iterators[i] = segment.AnEmptyPostingsIterator
continue OUTER
}
docNum1HitLast = docNum1Hit
docNum1HitLastOk = true
continue
}
if itr.ActualBM == nil {
// An empty actual bitmap means the entire AND is empty.
oTFR.iterators[i] = segment.AnEmptyPostingsIterator
continue OUTER
}
// Collect the actual bitmap for more processing later.
actualBMs = append(actualBMs, itr.ActualBM)
}
if docNum1HitLastOk {
// We reach here if all the 1-hit optimized posting
// iterators had the same 1-hit docNum, so we can check if
// our collected actual bitmaps also have that docNum.
for _, bm := range actualBMs {
if !bm.Contains(uint32(docNum1HitLast)) {
// The docNum1Hit isn't in one of our actual
// bitmaps, so the entire AND is empty.
oTFR.iterators[i] = segment.AnEmptyPostingsIterator
continue OUTER
}
}
// The actual bitmaps and docNum1Hits all contain or have
// the same 1-hit docNum, so that's our AND'ed result.
oTFR.iterators[i], err = zap.PostingsIteratorFrom1Hit(
docNum1HitLast, zap.NormBits1Hit, false, false)
if err != nil {
return nil, nil
}
continue OUTER
}
if len(actualBMs) == 0 {
// If we've collected no actual bitmaps at this point,
// then the entire AND is empty.
oTFR.iterators[i] = segment.AnEmptyPostingsIterator
continue OUTER
}
if len(actualBMs) == 1 {
// If we've only 1 actual bitmap, then that's our result.
oTFR.iterators[i], err = zap.PostingsIteratorFromBitmap(
actualBMs[0], false, false)
if err != nil {
return nil, nil
}
continue OUTER
}
// Else, AND together our collected bitmaps as our result.
bm := roaring.And(actualBMs[0], actualBMs[1])
for _, actualBM := range actualBMs[2:] {
bm.And(actualBM)
}
oTFR.iterators[i], err = zap.PostingsIteratorFromBitmap(
bm, false, false)
if err != nil {
return nil, nil
}
}
return oTFR, nil
}
// ----------------------------------------------------------------
// An "unadorned" disjunction optimization is appropriate when
// additional or subsidiary information like freq-norm's and
// term-vectors are not required, and instead only the internal-id's
// are needed.
func (s *IndexSnapshotTermFieldReader) optimizeDisjunctionUnadorned(
octx index.OptimizableContext) (index.OptimizableContext, error) {
if octx == nil {
octx = &OptimizeTFRDisjunctionUnadorned{snapshot: s.snapshot}
}
o, ok := octx.(*OptimizeTFRDisjunctionUnadorned)
if !ok {
return nil, nil
}
if o.snapshot != s.snapshot {
return nil, fmt.Errorf("tried to optimize unadorned disjunction across different snapshots")
}
o.tfrs = append(o.tfrs, s)
return o, nil
}
type OptimizeTFRDisjunctionUnadorned struct {
snapshot *IndexSnapshot
tfrs []*IndexSnapshotTermFieldReader
}
var OptimizeTFRDisjunctionUnadornedTerm = []byte("<disjunction:unadorned>")
var OptimizeTFRDisjunctionUnadornedField = "*"
// Finish of an unadorned disjunction optimization will compute a
// termFieldReader with an "actual" bitmap that represents the
// constituent bitmaps OR'ed together. This termFieldReader cannot
// provide any freq-norm or termVector associated information.
func (o *OptimizeTFRDisjunctionUnadorned) Finish() (rv index.Optimized, err error) {
if len(o.tfrs) <= 1 {
return nil, nil
}
for i := range o.snapshot.segment {
var cMax uint64
for _, tfr := range o.tfrs {
itr, ok := tfr.iterators[i].(*zap.PostingsIterator)
if !ok {
return nil, nil
}
if itr.ActualBM != nil {
c := itr.ActualBM.GetCardinality()
if cMax < c {
cMax = c
}
}
}
// Heuristic to skip the optimization if all the constituent
// bitmaps are too small, where the processing & resource
// overhead to create the OR'ed bitmap outweighs the benefit.
if cMax < OptimizeDisjunctionUnadornedMinChildCardinality {
return nil, nil
}
}
// We use an artificial term and field because the optimized
// termFieldReader can represent multiple terms and fields.
oTFR := &IndexSnapshotTermFieldReader{
term: OptimizeTFRDisjunctionUnadornedTerm,
field: OptimizeTFRDisjunctionUnadornedField,
snapshot: o.snapshot,
iterators: make([]segment.PostingsIterator, len(o.snapshot.segment)),
segmentOffset: 0,
includeFreq: false,
includeNorm: false,
includeTermVectors: false,
}
var docNums []uint32 // Collected docNum's from 1-hit posting lists.
var actualBMs []*roaring.Bitmap // Collected from regular posting lists.
for i := range o.snapshot.segment {
docNums = docNums[:0]
actualBMs = actualBMs[:0]
for _, tfr := range o.tfrs {
itr, ok := tfr.iterators[i].(*zap.PostingsIterator)
if !ok {
return nil, nil
}
docNum, ok := itr.DocNum1Hit()
if ok {
docNums = append(docNums, uint32(docNum))
continue
}
if itr.ActualBM != nil {
actualBMs = append(actualBMs, itr.ActualBM)
}
}
var bm *roaring.Bitmap
if len(actualBMs) > 2 {
bm = roaring.HeapOr(actualBMs...)
} else if len(actualBMs) == 2 {
bm = roaring.Or(actualBMs[0], actualBMs[1])
} else if len(actualBMs) == 1 {
bm = actualBMs[0].Clone()
}
if bm == nil {
bm = roaring.New()
}
bm.AddMany(docNums)
oTFR.iterators[i], err = zap.PostingsIteratorFromBitmap(bm, false, false)
if err != nil {
return nil, nil
}
}
return oTFR, nil
}