gitea/vendor/github.com/blevesearch/zapx/v14/posting.go
2021-02-28 18:08:33 -05:00

795 lines
20 KiB
Go
Vendored

// Copyright (c) 2017 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 zap
import (
"encoding/binary"
"fmt"
"math"
"reflect"
"github.com/RoaringBitmap/roaring"
segment "github.com/blevesearch/scorch_segment_api/v2"
)
var reflectStaticSizePostingsList int
var reflectStaticSizePostingsIterator int
var reflectStaticSizePosting int
var reflectStaticSizeLocation int
func init() {
var pl PostingsList
reflectStaticSizePostingsList = int(reflect.TypeOf(pl).Size())
var pi PostingsIterator
reflectStaticSizePostingsIterator = int(reflect.TypeOf(pi).Size())
var p Posting
reflectStaticSizePosting = int(reflect.TypeOf(p).Size())
var l Location
reflectStaticSizeLocation = int(reflect.TypeOf(l).Size())
}
// FST or vellum value (uint64) encoding is determined by the top two
// highest-order or most significant bits...
//
// encoding : MSB
// name : 63 62 61...to...bit #0 (LSB)
// ----------+---+---+---------------------------------------------------
// general : 0 | 0 | 62-bits of postingsOffset.
// ~ : 0 | 1 | reserved for future.
// 1-hit : 1 | 0 | 31-bits of positive float31 norm | 31-bits docNum.
// ~ : 1 | 1 | reserved for future.
//
// Encoding "general" is able to handle all cases, where the
// postingsOffset points to more information about the postings for
// the term.
//
// Encoding "1-hit" is used to optimize a commonly seen case when a
// term has only a single hit. For example, a term in the _id field
// will have only 1 hit. The "1-hit" encoding is used for a term
// in a field when...
//
// - term vector info is disabled for that field;
// - and, the term appears in only a single doc for that field;
// - and, the term's freq is exactly 1 in that single doc for that field;
// - and, the docNum must fit into 31-bits;
//
// Otherwise, the "general" encoding is used instead.
//
// In the "1-hit" encoding, the field in that single doc may have
// other terms, which is supported in the "1-hit" encoding by the
// positive float31 norm.
const FSTValEncodingMask = uint64(0xc000000000000000)
const FSTValEncodingGeneral = uint64(0x0000000000000000)
const FSTValEncoding1Hit = uint64(0x8000000000000000)
func FSTValEncode1Hit(docNum uint64, normBits uint64) uint64 {
return FSTValEncoding1Hit | ((mask31Bits & normBits) << 31) | (mask31Bits & docNum)
}
func FSTValDecode1Hit(v uint64) (docNum uint64, normBits uint64) {
return (mask31Bits & v), (mask31Bits & (v >> 31))
}
const mask31Bits = uint64(0x000000007fffffff)
func under32Bits(x uint64) bool {
return x <= mask31Bits
}
const DocNum1HitFinished = math.MaxUint64
var NormBits1Hit = uint64(math.Float32bits(float32(1)))
// PostingsList is an in-memory representation of a postings list
type PostingsList struct {
sb *SegmentBase
postingsOffset uint64
freqOffset uint64
locOffset uint64
postings *roaring.Bitmap
except *roaring.Bitmap
// when normBits1Hit != 0, then this postings list came from a
// 1-hit encoding, and only the docNum1Hit & normBits1Hit apply
docNum1Hit uint64
normBits1Hit uint64
chunkSize uint64
}
// represents an immutable, empty postings list
var emptyPostingsList = &PostingsList{}
func (p *PostingsList) Size() int {
sizeInBytes := reflectStaticSizePostingsList + SizeOfPtr
if p.except != nil {
sizeInBytes += int(p.except.GetSizeInBytes())
}
return sizeInBytes
}
func (p *PostingsList) OrInto(receiver *roaring.Bitmap) {
if p.normBits1Hit != 0 {
receiver.Add(uint32(p.docNum1Hit))
return
}
if p.postings != nil {
receiver.Or(p.postings)
}
}
// Iterator returns an iterator for this postings list
func (p *PostingsList) Iterator(includeFreq, includeNorm, includeLocs bool,
prealloc segment.PostingsIterator) segment.PostingsIterator {
if p.normBits1Hit == 0 && p.postings == nil {
return emptyPostingsIterator
}
var preallocPI *PostingsIterator
pi, ok := prealloc.(*PostingsIterator)
if ok && pi != nil {
preallocPI = pi
}
if preallocPI == emptyPostingsIterator {
preallocPI = nil
}
return p.iterator(includeFreq, includeNorm, includeLocs, preallocPI)
}
func (p *PostingsList) iterator(includeFreq, includeNorm, includeLocs bool,
rv *PostingsIterator) *PostingsIterator {
if rv == nil {
rv = &PostingsIterator{}
} else {
freqNormReader := rv.freqNormReader
if freqNormReader != nil {
freqNormReader.reset()
}
locReader := rv.locReader
if locReader != nil {
locReader.reset()
}
nextLocs := rv.nextLocs[:0]
nextSegmentLocs := rv.nextSegmentLocs[:0]
buf := rv.buf
*rv = PostingsIterator{} // clear the struct
rv.freqNormReader = freqNormReader
rv.locReader = locReader
rv.nextLocs = nextLocs
rv.nextSegmentLocs = nextSegmentLocs
rv.buf = buf
}
rv.postings = p
rv.includeFreqNorm = includeFreq || includeNorm || includeLocs
rv.includeLocs = includeLocs
if p.normBits1Hit != 0 {
// "1-hit" encoding
rv.docNum1Hit = p.docNum1Hit
rv.normBits1Hit = p.normBits1Hit
if p.except != nil && p.except.Contains(uint32(rv.docNum1Hit)) {
rv.docNum1Hit = DocNum1HitFinished
}
return rv
}
// "general" encoding, check if empty
if p.postings == nil {
return rv
}
// initialize freq chunk reader
if rv.includeFreqNorm {
rv.freqNormReader = newChunkedIntDecoder(p.sb.mem, p.freqOffset, rv.freqNormReader)
}
// initialize the loc chunk reader
if rv.includeLocs {
rv.locReader = newChunkedIntDecoder(p.sb.mem, p.locOffset, rv.locReader)
}
rv.all = p.postings.Iterator()
if p.except != nil {
rv.ActualBM = roaring.AndNot(p.postings, p.except)
rv.Actual = rv.ActualBM.Iterator()
} else {
rv.ActualBM = p.postings
rv.Actual = rv.all // Optimize to use same iterator for all & Actual.
}
return rv
}
// Count returns the number of items on this postings list
func (p *PostingsList) Count() uint64 {
var n, e uint64
if p.normBits1Hit != 0 {
n = 1
if p.except != nil && p.except.Contains(uint32(p.docNum1Hit)) {
e = 1
}
} else if p.postings != nil {
n = p.postings.GetCardinality()
if p.except != nil {
e = p.postings.AndCardinality(p.except)
}
}
return n - e
}
func (rv *PostingsList) read(postingsOffset uint64, d *Dictionary) error {
rv.postingsOffset = postingsOffset
// handle "1-hit" encoding special case
if rv.postingsOffset&FSTValEncodingMask == FSTValEncoding1Hit {
return rv.init1Hit(postingsOffset)
}
// read the location of the freq/norm details
var n uint64
var read int
rv.freqOffset, read = binary.Uvarint(d.sb.mem[postingsOffset+n : postingsOffset+binary.MaxVarintLen64])
n += uint64(read)
rv.locOffset, read = binary.Uvarint(d.sb.mem[postingsOffset+n : postingsOffset+n+binary.MaxVarintLen64])
n += uint64(read)
var postingsLen uint64
postingsLen, read = binary.Uvarint(d.sb.mem[postingsOffset+n : postingsOffset+n+binary.MaxVarintLen64])
n += uint64(read)
roaringBytes := d.sb.mem[postingsOffset+n : postingsOffset+n+postingsLen]
if rv.postings == nil {
rv.postings = roaring.NewBitmap()
}
_, err := rv.postings.FromBuffer(roaringBytes)
if err != nil {
return fmt.Errorf("error loading roaring bitmap: %v", err)
}
rv.chunkSize, err = getChunkSize(d.sb.chunkMode,
rv.postings.GetCardinality(), d.sb.numDocs)
if err != nil {
return err
}
return nil
}
func (rv *PostingsList) init1Hit(fstVal uint64) error {
docNum, normBits := FSTValDecode1Hit(fstVal)
rv.docNum1Hit = docNum
rv.normBits1Hit = normBits
return nil
}
// PostingsIterator provides a way to iterate through the postings list
type PostingsIterator struct {
postings *PostingsList
all roaring.IntPeekable
Actual roaring.IntPeekable
ActualBM *roaring.Bitmap
currChunk uint32
freqNormReader *chunkedIntDecoder
locReader *chunkedIntDecoder
next Posting // reused across Next() calls
nextLocs []Location // reused across Next() calls
nextSegmentLocs []segment.Location // reused across Next() calls
docNum1Hit uint64
normBits1Hit uint64
buf []byte
includeFreqNorm bool
includeLocs bool
}
var emptyPostingsIterator = &PostingsIterator{}
func (i *PostingsIterator) Size() int {
sizeInBytes := reflectStaticSizePostingsIterator + SizeOfPtr +
i.next.Size()
// account for freqNormReader, locReader if we start using this.
for _, entry := range i.nextLocs {
sizeInBytes += entry.Size()
}
return sizeInBytes
}
func (i *PostingsIterator) loadChunk(chunk int) error {
if i.includeFreqNorm {
err := i.freqNormReader.loadChunk(chunk)
if err != nil {
return err
}
}
if i.includeLocs {
err := i.locReader.loadChunk(chunk)
if err != nil {
return err
}
}
i.currChunk = uint32(chunk)
return nil
}
func (i *PostingsIterator) readFreqNormHasLocs() (uint64, uint64, bool, error) {
if i.normBits1Hit != 0 {
return 1, i.normBits1Hit, false, nil
}
freqHasLocs, err := i.freqNormReader.readUvarint()
if err != nil {
return 0, 0, false, fmt.Errorf("error reading frequency: %v", err)
}
freq, hasLocs := decodeFreqHasLocs(freqHasLocs)
normBits, err := i.freqNormReader.readUvarint()
if err != nil {
return 0, 0, false, fmt.Errorf("error reading norm: %v", err)
}
return freq, normBits, hasLocs, nil
}
func (i *PostingsIterator) skipFreqNormReadHasLocs() (bool, error) {
if i.normBits1Hit != 0 {
return false, nil
}
freqHasLocs, err := i.freqNormReader.readUvarint()
if err != nil {
return false, fmt.Errorf("error reading freqHasLocs: %v", err)
}
i.freqNormReader.SkipUvarint() // Skip normBits.
return freqHasLocs&0x01 != 0, nil // See decodeFreqHasLocs() / hasLocs.
}
func encodeFreqHasLocs(freq uint64, hasLocs bool) uint64 {
rv := freq << 1
if hasLocs {
rv = rv | 0x01 // 0'th LSB encodes whether there are locations
}
return rv
}
func decodeFreqHasLocs(freqHasLocs uint64) (uint64, bool) {
freq := freqHasLocs >> 1
hasLocs := freqHasLocs&0x01 != 0
return freq, hasLocs
}
// readLocation processes all the integers on the stream representing a single
// location.
func (i *PostingsIterator) readLocation(l *Location) error {
// read off field
fieldID, err := i.locReader.readUvarint()
if err != nil {
return fmt.Errorf("error reading location field: %v", err)
}
// read off pos
pos, err := i.locReader.readUvarint()
if err != nil {
return fmt.Errorf("error reading location pos: %v", err)
}
// read off start
start, err := i.locReader.readUvarint()
if err != nil {
return fmt.Errorf("error reading location start: %v", err)
}
// read off end
end, err := i.locReader.readUvarint()
if err != nil {
return fmt.Errorf("error reading location end: %v", err)
}
// read off num array pos
numArrayPos, err := i.locReader.readUvarint()
if err != nil {
return fmt.Errorf("error reading location num array pos: %v", err)
}
l.field = i.postings.sb.fieldsInv[fieldID]
l.pos = pos
l.start = start
l.end = end
if cap(l.ap) < int(numArrayPos) {
l.ap = make([]uint64, int(numArrayPos))
} else {
l.ap = l.ap[:int(numArrayPos)]
}
// read off array positions
for k := 0; k < int(numArrayPos); k++ {
ap, err := i.locReader.readUvarint()
if err != nil {
return fmt.Errorf("error reading array position: %v", err)
}
l.ap[k] = ap
}
return nil
}
// Next returns the next posting on the postings list, or nil at the end
func (i *PostingsIterator) Next() (segment.Posting, error) {
return i.nextAtOrAfter(0)
}
// Advance returns the posting at the specified docNum or it is not present
// the next posting, or if the end is reached, nil
func (i *PostingsIterator) Advance(docNum uint64) (segment.Posting, error) {
return i.nextAtOrAfter(docNum)
}
// Next returns the next posting on the postings list, or nil at the end
func (i *PostingsIterator) nextAtOrAfter(atOrAfter uint64) (segment.Posting, error) {
docNum, exists, err := i.nextDocNumAtOrAfter(atOrAfter)
if err != nil || !exists {
return nil, err
}
i.next = Posting{} // clear the struct
rv := &i.next
rv.docNum = docNum
if !i.includeFreqNorm {
return rv, nil
}
var normBits uint64
var hasLocs bool
rv.freq, normBits, hasLocs, err = i.readFreqNormHasLocs()
if err != nil {
return nil, err
}
rv.norm = math.Float32frombits(uint32(normBits))
if i.includeLocs && hasLocs {
// prepare locations into reused slices, where we assume
// rv.freq >= "number of locs", since in a composite field,
// some component fields might have their IncludeTermVector
// flags disabled while other component fields are enabled
if cap(i.nextLocs) >= int(rv.freq) {
i.nextLocs = i.nextLocs[0:rv.freq]
} else {
i.nextLocs = make([]Location, rv.freq, rv.freq*2)
}
if cap(i.nextSegmentLocs) < int(rv.freq) {
i.nextSegmentLocs = make([]segment.Location, rv.freq, rv.freq*2)
}
rv.locs = i.nextSegmentLocs[:0]
numLocsBytes, err := i.locReader.readUvarint()
if err != nil {
return nil, fmt.Errorf("error reading location numLocsBytes: %v", err)
}
j := 0
startBytesRemaining := i.locReader.Len() // # bytes remaining in the locReader
for startBytesRemaining-i.locReader.Len() < int(numLocsBytes) {
err := i.readLocation(&i.nextLocs[j])
if err != nil {
return nil, err
}
rv.locs = append(rv.locs, &i.nextLocs[j])
j++
}
}
return rv, nil
}
// nextDocNum returns the next docNum on the postings list, and also
// sets up the currChunk / loc related fields of the iterator.
func (i *PostingsIterator) nextDocNumAtOrAfter(atOrAfter uint64) (uint64, bool, error) {
if i.normBits1Hit != 0 {
if i.docNum1Hit == DocNum1HitFinished {
return 0, false, nil
}
if i.docNum1Hit < atOrAfter {
// advanced past our 1-hit
i.docNum1Hit = DocNum1HitFinished // consume our 1-hit docNum
return 0, false, nil
}
docNum := i.docNum1Hit
i.docNum1Hit = DocNum1HitFinished // consume our 1-hit docNum
return docNum, true, nil
}
if i.Actual == nil || !i.Actual.HasNext() {
return 0, false, nil
}
if i.postings == nil || i.postings.postings == i.ActualBM {
return i.nextDocNumAtOrAfterClean(atOrAfter)
}
i.Actual.AdvanceIfNeeded(uint32(atOrAfter))
if !i.Actual.HasNext() {
// couldn't find anything
return 0, false, nil
}
n := i.Actual.Next()
allN := i.all.Next()
nChunk := n / uint32(i.postings.chunkSize)
// when allN becomes >= to here, then allN is in the same chunk as nChunk.
allNReachesNChunk := nChunk * uint32(i.postings.chunkSize)
// n is the next actual hit (excluding some postings), and
// allN is the next hit in the full postings, and
// if they don't match, move 'all' forwards until they do
for allN != n {
// we've reached same chunk, so move the freq/norm/loc decoders forward
if i.includeFreqNorm && allN >= allNReachesNChunk {
err := i.currChunkNext(nChunk)
if err != nil {
return 0, false, err
}
}
allN = i.all.Next()
}
if i.includeFreqNorm && (i.currChunk != nChunk || i.freqNormReader.isNil()) {
err := i.loadChunk(int(nChunk))
if err != nil {
return 0, false, fmt.Errorf("error loading chunk: %v", err)
}
}
return uint64(n), true, nil
}
// optimization when the postings list is "clean" (e.g., no updates &
// no deletions) where the all bitmap is the same as the actual bitmap
func (i *PostingsIterator) nextDocNumAtOrAfterClean(
atOrAfter uint64) (uint64, bool, error) {
if !i.includeFreqNorm {
i.Actual.AdvanceIfNeeded(uint32(atOrAfter))
if !i.Actual.HasNext() {
return 0, false, nil // couldn't find anything
}
return uint64(i.Actual.Next()), true, nil
}
// freq-norm's needed, so maintain freq-norm chunk reader
sameChunkNexts := 0 // # of times we called Next() in the same chunk
n := i.Actual.Next()
nChunk := n / uint32(i.postings.chunkSize)
for uint64(n) < atOrAfter && i.Actual.HasNext() {
n = i.Actual.Next()
nChunkPrev := nChunk
nChunk = n / uint32(i.postings.chunkSize)
if nChunk != nChunkPrev {
sameChunkNexts = 0
} else {
sameChunkNexts += 1
}
}
if uint64(n) < atOrAfter {
// couldn't find anything
return 0, false, nil
}
for j := 0; j < sameChunkNexts; j++ {
err := i.currChunkNext(nChunk)
if err != nil {
return 0, false, fmt.Errorf("error optimized currChunkNext: %v", err)
}
}
if i.currChunk != nChunk || i.freqNormReader.isNil() {
err := i.loadChunk(int(nChunk))
if err != nil {
return 0, false, fmt.Errorf("error loading chunk: %v", err)
}
}
return uint64(n), true, nil
}
func (i *PostingsIterator) currChunkNext(nChunk uint32) error {
if i.currChunk != nChunk || i.freqNormReader.isNil() {
err := i.loadChunk(int(nChunk))
if err != nil {
return fmt.Errorf("error loading chunk: %v", err)
}
}
// read off freq/offsets even though we don't care about them
hasLocs, err := i.skipFreqNormReadHasLocs()
if err != nil {
return err
}
if i.includeLocs && hasLocs {
numLocsBytes, err := i.locReader.readUvarint()
if err != nil {
return fmt.Errorf("error reading location numLocsBytes: %v", err)
}
// skip over all the location bytes
i.locReader.SkipBytes(int(numLocsBytes))
}
return nil
}
// DocNum1Hit returns the docNum and true if this is "1-hit" optimized
// and the docNum is available.
func (p *PostingsIterator) DocNum1Hit() (uint64, bool) {
if p.normBits1Hit != 0 && p.docNum1Hit != DocNum1HitFinished {
return p.docNum1Hit, true
}
return 0, false
}
// ActualBitmap returns the underlying actual bitmap
// which can be used up the stack for optimizations
func (p *PostingsIterator) ActualBitmap() *roaring.Bitmap {
return p.ActualBM
}
// ReplaceActual replaces the ActualBM with the provided
// bitmap
func (p *PostingsIterator) ReplaceActual(abm *roaring.Bitmap) {
p.ActualBM = abm
p.Actual = abm.Iterator()
}
// PostingsIteratorFromBitmap constructs a PostingsIterator given an
// "actual" bitmap.
func PostingsIteratorFromBitmap(bm *roaring.Bitmap,
includeFreqNorm, includeLocs bool) (segment.PostingsIterator, error) {
return &PostingsIterator{
ActualBM: bm,
Actual: bm.Iterator(),
includeFreqNorm: includeFreqNorm,
includeLocs: includeLocs,
}, nil
}
// PostingsIteratorFrom1Hit constructs a PostingsIterator given a
// 1-hit docNum.
func PostingsIteratorFrom1Hit(docNum1Hit uint64,
includeFreqNorm, includeLocs bool) (segment.PostingsIterator, error) {
return &PostingsIterator{
docNum1Hit: docNum1Hit,
normBits1Hit: NormBits1Hit,
includeFreqNorm: includeFreqNorm,
includeLocs: includeLocs,
}, nil
}
// Posting is a single entry in a postings list
type Posting struct {
docNum uint64
freq uint64
norm float32
locs []segment.Location
}
func (p *Posting) Size() int {
sizeInBytes := reflectStaticSizePosting
for _, entry := range p.locs {
sizeInBytes += entry.Size()
}
return sizeInBytes
}
// Number returns the document number of this posting in this segment
func (p *Posting) Number() uint64 {
return p.docNum
}
// Frequency returns the frequencies of occurrence of this term in this doc/field
func (p *Posting) Frequency() uint64 {
return p.freq
}
// Norm returns the normalization factor for this posting
func (p *Posting) Norm() float64 {
return float64(p.norm)
}
// Locations returns the location information for each occurrence
func (p *Posting) Locations() []segment.Location {
return p.locs
}
// Location represents the location of a single occurrence
type Location struct {
field string
pos uint64
start uint64
end uint64
ap []uint64
}
func (l *Location) Size() int {
return reflectStaticSizeLocation +
len(l.field) +
len(l.ap)*SizeOfUint64
}
// Field returns the name of the field (useful in composite fields to know
// which original field the value came from)
func (l *Location) Field() string {
return l.field
}
// Start returns the start byte offset of this occurrence
func (l *Location) Start() uint64 {
return l.start
}
// End returns the end byte offset of this occurrence
func (l *Location) End() uint64 {
return l.end
}
// Pos returns the 1-based phrase position of this occurrence
func (l *Location) Pos() uint64 {
return l.pos
}
// ArrayPositions returns the array position vector associated with this occurrence
func (l *Location) ArrayPositions() []uint64 {
return l.ap
}