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docidsetbuilder.go
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/
docidsetbuilder.go
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package search
import (
"errors"
"github.com/bits-and-blooms/bitset"
"github.com/geange/lucene-go/core/index"
"github.com/geange/lucene-go/core/types"
"github.com/geange/lucene-go/core/util/array"
"io"
"math"
"sort"
)
// DocIdSetBuilder
// A builder of DocIdSets. At first it uses a sparse structure to gather documents,
// and then upgrades to a non-sparse bit set once enough hits match. To add documents,
// you first need to call grow in order to reserve space, and then call
// DocIdSetBuilder.BulkAdder.add(int) on the returned DocIdSetBuilder.BulkAdder.
// lucene.internal
type DocIdSetBuilder struct {
maxDoc int
threshold int
// pkg-private for testing
multivalued bool
numValuesPerDoc float64
buffers []*Buffer
// accumulated size of the allocated buffers
totalAllocated int
bitSet *bitset.BitSet
counter int64
adder BulkAdder
}
// NewDocIdSetBuilder Create a builder that can contain doc IDs between 0 and maxDoc.
func NewDocIdSetBuilder(maxDoc int) *DocIdSetBuilder {
return newDocIdSetBuilder(maxDoc, -1, -1)
}
// NewDocIdSetBuilderV1
// Create a DocIdSetBuilder instance that is optimized for accumulating docs that match the given Terms.
func NewDocIdSetBuilderV1(maxDoc int, terms index.Terms) (*DocIdSetBuilder, error) {
docCount, err := terms.GetDocCount()
if err != nil {
return nil, err
}
sumDocFreq, err := terms.GetSumDocFreq()
if err != nil {
return nil, err
}
return newDocIdSetBuilder(maxDoc, docCount, sumDocFreq), nil
}
// NewDocIdSetBuilderV2
// Create a DocIdSetBuilder instance that is optimized for accumulating docs that match the given PointValues.
func NewDocIdSetBuilderV2(maxDoc int, values types.PointValues, field string) *DocIdSetBuilder {
return newDocIdSetBuilder(maxDoc, values.GetDocCount(), int64(values.Size()))
}
func newDocIdSetBuilder(maxDoc, docCount int, valueCount int64) *DocIdSetBuilder {
builder := &DocIdSetBuilder{
maxDoc: maxDoc,
multivalued: docCount < 0 || int64(docCount) != valueCount,
}
if docCount <= 0 || valueCount < 0 {
// assume one value per doc, this means the cost will be overestimated
// if the docs are actually multi-valued
builder.numValuesPerDoc = 1
} else {
// otherwise compute from index stats
builder.numValuesPerDoc = float64(valueCount) / float64(docCount)
}
// For ridiculously small sets, we'll just use a sorted int[]
// maxDoc >>> 7 is a good value if you want to save memory, lower values
// such as maxDoc >>> 11 should provide faster building but at the expense
// of using a full bitset even for quite sparse data
builder.threshold = maxDoc >> 7
return builder
}
// Add the content of the provided DocIdSetIterator to this builder.
// NOTE: if you need to build a DocIdSet out of a single DocIdSetIterator,
// you should rather use RoaringDocIdSet.Builder.
func (d *DocIdSetBuilder) Add(iter types.DocIdSetIterator) error {
if d.bitSet != nil {
it, ok := iter.(*index.BitSetIterator)
if ok {
d.bitSet = d.bitSet.Union(it.GetBitSet())
} else {
for {
doc, err := iter.NextDoc()
if err != nil {
if errors.Is(err, io.EOF) {
return nil
}
return err
}
d.bitSet.Set(uint(doc))
}
}
return nil
}
cost := int(min(math.MaxInt32, iter.Cost()))
adder := d.Grow(cost)
for i := 0; i < cost; i++ {
doc, err := iter.NextDoc()
if err != nil {
if errors.Is(err, io.EOF) {
return nil
}
return err
}
adder.Add(doc)
}
for {
doc, err := iter.NextDoc()
if err != nil {
if errors.Is(err, io.EOF) {
return nil
}
return err
}
d.adder.Add(doc)
}
}
// Grow
// Reserve space and return a DocIdSetBuilder.BulkAdder object
// that can be used to add up to numDocs documents.
func (d *DocIdSetBuilder) Grow(numDocs int) BulkAdder {
if d.bitSet != nil {
d.counter += int64(numDocs)
} else {
if d.totalAllocated+numDocs <= d.threshold {
d.ensureBufferCapacity(numDocs)
} else {
d.upgradeToBitSet()
d.counter += int64(numDocs)
}
}
return d.adder
}
func (d *DocIdSetBuilder) ensureBufferCapacity(numDocs int) {
if len(d.buffers) == 0 {
d.addBuffer(d.additionalCapacity(numDocs))
return
}
current := d.buffers[len(d.buffers)-1]
if len(current.array)-current.length >= numDocs {
// current buffer is large enough
return
}
if current.length < len(current.array)-len(current.array)>>3 {
// current buffer is less than 7/8 full, resize rather than waste space
d.growBuffer(current, d.additionalCapacity(numDocs))
} else {
d.addBuffer(d.additionalCapacity(numDocs))
}
}
func (d *DocIdSetBuilder) additionalCapacity(numDocs int) int {
// exponential growth: the new array has a size equal to the sum of what
// has been allocated so far
c := d.totalAllocated
// but is also >= numDocs + 1 so that we can store the next batch of docs
// (plus an empty slot so that we are more likely to reuse the array in build())
c = max(numDocs+1, c)
// avoid cold starts
c = max(32, c)
// do not go beyond the threshold
c = min(d.threshold-d.totalAllocated, c)
return c
}
func (d *DocIdSetBuilder) addBuffer(size int) *Buffer {
buffer := NewBufferBySize(size)
d.buffers = append(d.buffers, buffer)
d.adder = NewBufferAdder(buffer)
d.totalAllocated += len(buffer.array)
return buffer
}
func (d *DocIdSetBuilder) growBuffer(buffer *Buffer, additionalCapacity int) {
newArray := make([]int, len(d.buffers)+additionalCapacity)
copy(newArray, buffer.array)
buffer.array = newArray
d.totalAllocated += additionalCapacity
}
func (d *DocIdSetBuilder) upgradeToBitSet() {
bitSet := bitset.New(uint(d.maxDoc))
counter := 0
for _, buffer := range d.buffers {
counter += buffer.length
for i := 0; i < buffer.length; i++ {
bitSet.Set(uint(buffer.array[i]))
}
}
d.bitSet = bitSet
d.counter = int64(counter)
d.buffers = nil
d.adder = NewFixedBitSetAdder(d.bitSet)
}
// Build a DocIdSet from the accumulated doc IDs.
func (d *DocIdSetBuilder) Build() DocIdSet {
if d.bitSet != nil {
cost := math.Round(float64(d.counter) / d.numValuesPerDoc)
return NewBitDocIdSet(d.bitSet, int64(cost))
}
concatenated := concatBuffers(d.buffers)
sort.Ints(concatenated.array)
//concatenated.array[l] = index.NO_MORE_DOCS
return NewIntArrayDocIdSet(concatenated.array[:concatenated.length])
}
// Concatenate the buffers in any order, leaving at least one empty slot in the end
// NOTE: this method might reuse one of the arrays
func concatBuffers(buffers []*Buffer) *Buffer {
totalLength := 0
var largestBuffer *Buffer
for _, buffer := range buffers {
totalLength += buffer.length
if largestBuffer == nil || len(buffer.array) > len(largestBuffer.array) {
largestBuffer = buffer
}
}
if largestBuffer == nil {
return NewBufferBySize(0)
}
docs := largestBuffer.array
if len(docs) < totalLength {
docs = array.GrowExact(docs, totalLength)
}
totalLength = largestBuffer.length
for _, buffer := range buffers {
if buffer != largestBuffer {
copy(docs[totalLength:], buffer.array)
}
}
return NewBuffer(docs, totalLength)
}
func dedup(arr []int, length int) int {
if length == 0 {
return 0
}
l := 1
previous := arr[0]
for i := 1; i < length; i++ {
value := arr[i]
//assert value >= previous;
if value != previous {
arr[l] = value
l++
previous = value
}
}
return l
}
func noDups(arr []int, length int) bool {
for i := 1; i < length; i++ {
if arr[i-1] < arr[i] {
return false
}
}
return true
}
// BulkAdder Utility class to efficiently add many docs in one go.
// See Also: grow
type BulkAdder interface {
Add(doc int)
}
type FixedBitSetAdder struct {
bitSet *bitset.BitSet
}
func NewFixedBitSetAdder(bitSet *bitset.BitSet) *FixedBitSetAdder {
return &FixedBitSetAdder{bitSet: bitSet}
}
func (f *FixedBitSetAdder) Add(doc int) {
f.bitSet.Set(uint(doc))
}
type Buffer struct {
array []int
length int
}
func NewBuffer(array []int, length int) *Buffer {
return &Buffer{
array: array,
length: length,
}
}
func NewBufferBySize(size int) *Buffer {
return &Buffer{
array: make([]int, size),
length: 0,
}
}
var _ BulkAdder = &BufferAdder{}
type BufferAdder struct {
buffer *Buffer
}
func NewBufferAdder(buffer *Buffer) *BufferAdder {
return &BufferAdder{buffer: buffer}
}
func (b *BufferAdder) Add(doc int) {
b.buffer.array[b.buffer.length] = doc
b.buffer.length++
}