forked from blevesearch/bleve
/
merge.go
531 lines (466 loc) · 13.7 KB
/
merge.go
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// 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 (
"bufio"
"bytes"
"encoding/binary"
"fmt"
"math"
"os"
"sort"
"github.com/RoaringBitmap/roaring"
"github.com/Smerity/govarint"
"github.com/couchbase/vellum"
"github.com/golang/snappy"
)
// Merge takes a slice of zap segments, bit masks describing which documents
// from the may be dropped, and creates a new segment containing the remaining
// data. This new segment is built at the specified path, with the provided
// chunkFactor.
func Merge(segments []*Segment, drops []*roaring.Bitmap, path string,
chunkFactor uint32) ([][]uint64, error) {
flag := os.O_RDWR | os.O_CREATE
f, err := os.OpenFile(path, flag, 0600)
if err != nil {
return nil, err
}
// buffer the output
br := bufio.NewWriter(f)
// wrap it for counting (tracking offsets)
cr := NewCountHashWriter(br)
fieldsInv := mergeFields(segments)
fieldsMap := mapFields(fieldsInv)
newSegDocCount := computeNewDocCount(segments, drops)
var newDocNums [][]uint64
var storedIndexOffset uint64
fieldDvLocsOffset := uint64(fieldNotUninverted)
var dictLocs []uint64
if newSegDocCount > 0 {
storedIndexOffset, newDocNums, err = mergeStoredAndRemap(segments, drops,
fieldsMap, fieldsInv, newSegDocCount, cr)
if err != nil {
return nil, err
}
dictLocs, fieldDvLocsOffset, err = persistMergedRest(segments, drops, fieldsInv, fieldsMap,
newDocNums, newSegDocCount, chunkFactor, cr)
if err != nil {
return nil, err
}
} else {
dictLocs = make([]uint64, len(fieldsInv))
}
var fieldsIndexOffset uint64
fieldsIndexOffset, err = persistFields(fieldsInv, cr, dictLocs)
if err != nil {
return nil, err
}
err = persistFooter(newSegDocCount, storedIndexOffset,
fieldsIndexOffset, fieldDvLocsOffset, chunkFactor, cr)
if err != nil {
return nil, err
}
err = br.Flush()
if err != nil {
return nil, err
}
err = f.Sync()
if err != nil {
return nil, err
}
err = f.Close()
if err != nil {
return nil, err
}
return newDocNums, nil
}
// mapFields takes the fieldsInv list and builds the map
func mapFields(fields []string) map[string]uint16 {
rv := make(map[string]uint16)
for i, fieldName := range fields {
rv[fieldName] = uint16(i)
}
return rv
}
// computeNewDocCount determines how many documents will be in the newly
// merged segment when obsoleted docs are dropped
func computeNewDocCount(segments []*Segment, drops []*roaring.Bitmap) uint64 {
var newSegDocCount uint64
for segI, segment := range segments {
segIAfterDrop := segment.NumDocs()
if drops[segI] != nil {
segIAfterDrop -= drops[segI].GetCardinality()
}
newSegDocCount += segIAfterDrop
}
return newSegDocCount
}
func persistMergedRest(segments []*Segment, drops []*roaring.Bitmap,
fieldsInv []string, fieldsMap map[string]uint16, newDocNums [][]uint64,
newSegDocCount uint64, chunkFactor uint32,
w *CountHashWriter) ([]uint64, uint64, error) {
var bufMaxVarintLen64 []byte = make([]byte, binary.MaxVarintLen64)
var bufLoc []uint64
rv1 := make([]uint64, len(fieldsInv))
fieldDvLocs := make([]uint64, len(fieldsInv))
fieldDvLocsOffset := uint64(fieldNotUninverted)
var vellumBuf bytes.Buffer
// for each field
for fieldID, fieldName := range fieldsInv {
if fieldID != 0 {
vellumBuf.Reset()
}
newVellum, err := vellum.New(&vellumBuf, nil)
if err != nil {
return nil, 0, err
}
// collect FST iterators from all segments for this field
var dicts []*Dictionary
var itrs []vellum.Iterator
for _, segment := range segments {
dict, err2 := segment.dictionary(fieldName)
if err2 != nil {
return nil, 0, err2
}
dicts = append(dicts, dict)
if dict != nil && dict.fst != nil {
itr, err2 := dict.fst.Iterator(nil, nil)
if err2 != nil && err2 != vellum.ErrIteratorDone {
return nil, 0, err2
}
if itr != nil {
itrs = append(itrs, itr)
}
}
}
// create merging iterator
mergeItr, err := vellum.NewMergeIterator(itrs, func(postingOffsets []uint64) uint64 {
// we don't actually use the merged value
return 0
})
tfEncoder := newChunkedIntCoder(uint64(chunkFactor), newSegDocCount-1)
locEncoder := newChunkedIntCoder(uint64(chunkFactor), newSegDocCount-1)
fdvEncoder := newChunkedContentCoder(uint64(chunkFactor), newSegDocCount-1)
docTermMap := make(map[uint64][]byte, 0)
for err == nil {
term, _ := mergeItr.Current()
newRoaring := roaring.NewBitmap()
newRoaringLocs := roaring.NewBitmap()
tfEncoder.Reset()
locEncoder.Reset()
// now go back and get posting list for this term
// but pass in the deleted docs for that segment
for dictI, dict := range dicts {
if dict == nil {
continue
}
postings, err2 := dict.postingsList(string(term), drops[dictI])
if err2 != nil {
return nil, 0, err2
}
postItr := postings.Iterator()
next, err2 := postItr.Next()
for next != nil && err2 == nil {
hitNewDocNum := newDocNums[dictI][next.Number()]
if hitNewDocNum == docDropped {
return nil, 0, fmt.Errorf("see hit with dropped doc num")
}
newRoaring.Add(uint32(hitNewDocNum))
// encode norm bits
norm := next.Norm()
normBits := math.Float32bits(float32(norm))
err3 := tfEncoder.Add(hitNewDocNum, next.Frequency(), uint64(normBits))
if err3 != nil {
return nil, 0, err3
}
locs := next.Locations()
if len(locs) > 0 {
newRoaringLocs.Add(uint32(hitNewDocNum))
for _, loc := range locs {
if cap(bufLoc) < 5+len(loc.ArrayPositions()) {
bufLoc = make([]uint64, 0, 5+len(loc.ArrayPositions()))
}
args := bufLoc[0:0]
args = append(args, uint64(fieldsMap[loc.Field()]))
args = append(args, loc.Pos())
args = append(args, loc.Start())
args = append(args, loc.End())
args = append(args, uint64(len(loc.ArrayPositions())))
args = append(args, loc.ArrayPositions()...)
err = locEncoder.Add(hitNewDocNum, args...)
if err != nil {
return nil, 0, err
}
}
}
docTermMap[hitNewDocNum] = append(docTermMap[hitNewDocNum], []byte(term)...)
docTermMap[hitNewDocNum] = append(docTermMap[hitNewDocNum], termSeparator)
next, err2 = postItr.Next()
}
if err != nil {
return nil, 0, err
}
}
tfEncoder.Close()
locEncoder.Close()
if newRoaring.GetCardinality() > 0 {
// this field/term actually has hits in the new segment, lets write it down
freqOffset := uint64(w.Count())
_, err = tfEncoder.Write(w)
if err != nil {
return nil, 0, err
}
locOffset := uint64(w.Count())
_, err = locEncoder.Write(w)
if err != nil {
return nil, 0, err
}
postingLocOffset := uint64(w.Count())
_, err = writeRoaringWithLen(newRoaringLocs, w)
if err != nil {
return nil, 0, err
}
postingOffset := uint64(w.Count())
// write out the start of the term info
buf := bufMaxVarintLen64
n := binary.PutUvarint(buf, freqOffset)
_, err = w.Write(buf[:n])
if err != nil {
return nil, 0, err
}
// write out the start of the loc info
n = binary.PutUvarint(buf, locOffset)
_, err = w.Write(buf[:n])
if err != nil {
return nil, 0, err
}
// write out the start of the loc posting list
n = binary.PutUvarint(buf, postingLocOffset)
_, err = w.Write(buf[:n])
if err != nil {
return nil, 0, err
}
_, err = writeRoaringWithLen(newRoaring, w)
if err != nil {
return nil, 0, err
}
err = newVellum.Insert(term, postingOffset)
if err != nil {
return nil, 0, err
}
}
err = mergeItr.Next()
}
if err != nil && err != vellum.ErrIteratorDone {
return nil, 0, err
}
dictOffset := uint64(w.Count())
err = newVellum.Close()
if err != nil {
return nil, 0, err
}
vellumData := vellumBuf.Bytes()
// write out the length of the vellum data
buf := bufMaxVarintLen64
// write out the number of chunks
n := binary.PutUvarint(buf, uint64(len(vellumData)))
_, err = w.Write(buf[:n])
if err != nil {
return nil, 0, err
}
// write this vellum to disk
_, err = w.Write(vellumData)
if err != nil {
return nil, 0, err
}
rv1[fieldID] = dictOffset
// update the doc value
var docNumbers docIDRange
for k := range docTermMap {
docNumbers = append(docNumbers, k)
}
sort.Sort(docNumbers)
for _, docNum := range docNumbers {
err = fdvEncoder.Add(docNum, docTermMap[docNum])
if err != nil {
return nil, 0, err
}
}
// get the field doc value offset
fieldDvLocs[fieldID] = uint64(w.Count())
err = fdvEncoder.Close()
if err != nil {
return nil, 0, err
}
// persist the doc value details for this field
_, err = fdvEncoder.Write(w)
if err != nil {
return nil, 0, err
}
}
fieldDvLocsOffset = uint64(w.Count())
buf := make([]byte, binary.MaxVarintLen64)
for _, offset := range fieldDvLocs {
n := binary.PutUvarint(buf, uint64(offset))
_, err := w.Write(buf[:n])
if err != nil {
return nil, 0, err
}
}
return rv1, fieldDvLocsOffset, nil
}
const docDropped = math.MaxUint64
func mergeStoredAndRemap(segments []*Segment, drops []*roaring.Bitmap,
fieldsMap map[string]uint16, fieldsInv []string, newSegDocCount uint64,
w *CountHashWriter) (uint64, [][]uint64, error) {
var rv [][]uint64
var newDocNum int
var curr int
var metaBuf bytes.Buffer
var data, compressed []byte
vals := make([][][]byte, len(fieldsInv))
typs := make([][]byte, len(fieldsInv))
poss := make([][][]uint64, len(fieldsInv))
docNumOffsets := make([]uint64, newSegDocCount)
// for each segment
for segI, segment := range segments {
var segNewDocNums []uint64
// for each doc num
for docNum := uint64(0); docNum < segment.numDocs; docNum++ {
metaBuf.Reset()
data = data[:0]
compressed = compressed[:0]
curr = 0
metaEncoder := govarint.NewU64Base128Encoder(&metaBuf)
if drops[segI] != nil && drops[segI].Contains(uint32(docNum)) {
segNewDocNums = append(segNewDocNums, docDropped)
} else {
segNewDocNums = append(segNewDocNums, uint64(newDocNum))
// collect all the data
for i := 0; i < len(fieldsInv); i++ {
vals[i] = vals[i][:0]
typs[i] = typs[i][:0]
poss[i] = poss[i][:0]
}
err := segment.VisitDocument(docNum, func(field string, typ byte, value []byte, pos []uint64) bool {
fieldID := int(fieldsMap[field])
vals[fieldID] = append(vals[fieldID], value)
typs[fieldID] = append(typs[fieldID], typ)
poss[fieldID] = append(poss[fieldID], pos)
return true
})
if err != nil {
return 0, nil, err
}
// now walk the fields in order
for fieldID := range fieldsInv {
storedFieldValues := vals[int(fieldID)]
// has stored values for this field
num := len(storedFieldValues)
// process each value
for i := 0; i < num; i++ {
// encode field
_, err2 := metaEncoder.PutU64(uint64(fieldID))
if err2 != nil {
return 0, nil, err2
}
// encode type
_, err2 = metaEncoder.PutU64(uint64(typs[int(fieldID)][i]))
if err2 != nil {
return 0, nil, err2
}
// encode start offset
_, err2 = metaEncoder.PutU64(uint64(curr))
if err2 != nil {
return 0, nil, err2
}
// end len
_, err2 = metaEncoder.PutU64(uint64(len(storedFieldValues[i])))
if err2 != nil {
return 0, nil, err2
}
// encode number of array pos
_, err2 = metaEncoder.PutU64(uint64(len(poss[int(fieldID)][i])))
if err2 != nil {
return 0, nil, err2
}
// encode all array positions
for j := 0; j < len(poss[int(fieldID)][i]); j++ {
_, err2 = metaEncoder.PutU64(poss[int(fieldID)][i][j])
if err2 != nil {
return 0, nil, err2
}
}
// append data
data = append(data, storedFieldValues[i]...)
// update curr
curr += len(storedFieldValues[i])
}
}
metaEncoder.Close()
metaBytes := metaBuf.Bytes()
compressed = snappy.Encode(compressed, data)
// record where we're about to start writing
docNumOffsets[newDocNum] = uint64(w.Count())
// write out the meta len and compressed data len
_, err = writeUvarints(w,
uint64(len(metaBytes)), uint64(len(compressed)))
if err != nil {
return 0, nil, err
}
// now write the meta
_, err = w.Write(metaBytes)
if err != nil {
return 0, nil, err
}
// now write the compressed data
_, err = w.Write(compressed)
if err != nil {
return 0, nil, err
}
newDocNum++
}
}
rv = append(rv, segNewDocNums)
}
// return value is the start of the stored index
offset := uint64(w.Count())
// now write out the stored doc index
for docNum := range docNumOffsets {
err := binary.Write(w, binary.BigEndian, docNumOffsets[docNum])
if err != nil {
return 0, nil, err
}
}
return offset, rv, nil
}
// mergeFields builds a unified list of fields used across all the input segments
func mergeFields(segments []*Segment) []string {
fieldsMap := map[string]struct{}{}
for _, segment := range segments {
fields := segment.Fields()
for _, field := range fields {
fieldsMap[field] = struct{}{}
}
}
rv := make([]string, 0, len(fieldsMap))
// ensure _id stays first
rv = append(rv, "_id")
for k := range fieldsMap {
if k != "_id" {
rv = append(rv, k)
}
}
return rv
}