forked from blevesearch/bleve
/
segment.go
459 lines (391 loc) · 11.5 KB
/
segment.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 (
"bytes"
"encoding/binary"
"fmt"
"io"
"os"
"sync"
"github.com/RoaringBitmap/roaring"
"github.com/Smerity/govarint"
"github.com/blevesearch/bleve/index/scorch/segment"
"github.com/couchbase/vellum"
mmap "github.com/edsrzf/mmap-go"
"github.com/golang/snappy"
)
// Open returns a zap impl of a segment
func Open(path string) (segment.Segment, error) {
f, err := os.Open(path)
if err != nil {
return nil, err
}
mm, err := mmap.Map(f, mmap.RDONLY, 0)
if err != nil {
// mmap failed, try to close the file
_ = f.Close()
return nil, err
}
rv := &Segment{
SegmentBase: SegmentBase{
mem: mm[0 : len(mm)-FooterSize],
fieldsMap: make(map[string]uint16),
fieldDvIterMap: make(map[uint16]*docValueIterator),
},
f: f,
mm: mm,
path: path,
refs: 1,
}
err = rv.loadConfig()
if err != nil {
_ = rv.Close()
return nil, err
}
err = rv.loadFields()
if err != nil {
_ = rv.Close()
return nil, err
}
err = rv.loadDvIterators()
if err != nil {
_ = rv.Close()
return nil, err
}
return rv, nil
}
// SegmentBase is a memory only, read-only implementation of the
// segment.Segment interface, using zap's data representation.
type SegmentBase struct {
mem []byte
memCRC uint32
chunkFactor uint32
fieldsMap map[string]uint16 // fieldName -> fieldID+1
fieldsInv []string // fieldID -> fieldName
numDocs uint64
storedIndexOffset uint64
fieldsIndexOffset uint64
docValueOffset uint64
dictLocs []uint64
fieldDvIterMap map[uint16]*docValueIterator // naive chunk cache per field
}
func (sb *SegmentBase) AddRef() {}
func (sb *SegmentBase) DecRef() (err error) { return nil }
func (sb *SegmentBase) Close() (err error) { return nil }
// Segment implements a persisted segment.Segment interface, by
// embedding an mmap()'ed SegmentBase.
type Segment struct {
SegmentBase
f *os.File
mm mmap.MMap
path string
version uint32
crc uint32
m sync.Mutex // Protects the fields that follow.
refs int64
}
func (s *Segment) SizeInBytes() uint64 {
// 8 /* size of file pointer */
// 4 /* size of version -> uint32 */
// 4 /* size of crc -> uint32 */
sizeOfUints := 16
sizeInBytes := (len(s.path) + int(segment.SizeOfString)) + sizeOfUints
// mutex, refs -> int64
sizeInBytes += 16
// do not include the mmap'ed part
return uint64(sizeInBytes) + s.SegmentBase.SizeInBytes() - uint64(len(s.mem))
}
func (s *SegmentBase) SizeInBytes() uint64 {
// 4 /* size of memCRC -> uint32 */
// 4 /* size of chunkFactor -> uint32 */
// 8 /* size of numDocs -> uint64 */
// 8 /* size of storedIndexOffset -> uint64 */
// 8 /* size of fieldsIndexOffset -> uint64 */
// 8 /* size of docValueOffset -> uint64 */
sizeInBytes := 40
sizeInBytes += len(s.mem) + int(segment.SizeOfSlice)
// fieldsMap
for k, _ := range s.fieldsMap {
sizeInBytes += (len(k) + int(segment.SizeOfString)) + 2 /* size of uint16 */
}
sizeInBytes += int(segment.SizeOfMap) /* overhead from map */
// fieldsInv, dictLocs
for _, entry := range s.fieldsInv {
sizeInBytes += (len(entry) + int(segment.SizeOfString))
}
sizeInBytes += len(s.dictLocs) * 8 /* size of uint64 */
sizeInBytes += int(segment.SizeOfSlice) * 3 /* overhead from slices */
// fieldDvIterMap
sizeInBytes += len(s.fieldDvIterMap) *
int(segment.SizeOfPointer+2 /* size of uint16 */)
for _, entry := range s.fieldDvIterMap {
if entry != nil {
sizeInBytes += int(entry.sizeInBytes())
}
}
sizeInBytes += int(segment.SizeOfMap)
return uint64(sizeInBytes)
}
func (s *Segment) AddRef() {
s.m.Lock()
s.refs++
s.m.Unlock()
}
func (s *Segment) DecRef() (err error) {
s.m.Lock()
s.refs--
if s.refs == 0 {
err = s.closeActual()
}
s.m.Unlock()
return err
}
func (s *Segment) loadConfig() error {
crcOffset := len(s.mm) - 4
s.crc = binary.BigEndian.Uint32(s.mm[crcOffset : crcOffset+4])
verOffset := crcOffset - 4
s.version = binary.BigEndian.Uint32(s.mm[verOffset : verOffset+4])
if s.version != version {
return fmt.Errorf("unsupported version %d", s.version)
}
chunkOffset := verOffset - 4
s.chunkFactor = binary.BigEndian.Uint32(s.mm[chunkOffset : chunkOffset+4])
docValueOffset := chunkOffset - 8
s.docValueOffset = binary.BigEndian.Uint64(s.mm[docValueOffset : docValueOffset+8])
fieldsIndexOffset := docValueOffset - 8
s.fieldsIndexOffset = binary.BigEndian.Uint64(s.mm[fieldsIndexOffset : fieldsIndexOffset+8])
storedIndexOffset := fieldsIndexOffset - 8
s.storedIndexOffset = binary.BigEndian.Uint64(s.mm[storedIndexOffset : storedIndexOffset+8])
numDocsOffset := storedIndexOffset - 8
s.numDocs = binary.BigEndian.Uint64(s.mm[numDocsOffset : numDocsOffset+8])
return nil
}
func (s *SegmentBase) loadFields() error {
// NOTE for now we assume the fields index immediately preceeds
// the footer, and if this changes, need to adjust accordingly (or
// store explicit length), where s.mem was sliced from s.mm in Open().
fieldsIndexEnd := uint64(len(s.mem))
// iterate through fields index
var fieldID uint64
for s.fieldsIndexOffset+(8*fieldID) < fieldsIndexEnd {
addr := binary.BigEndian.Uint64(s.mem[s.fieldsIndexOffset+(8*fieldID) : s.fieldsIndexOffset+(8*fieldID)+8])
dictLoc, read := binary.Uvarint(s.mem[addr:fieldsIndexEnd])
n := uint64(read)
s.dictLocs = append(s.dictLocs, dictLoc)
var nameLen uint64
nameLen, read = binary.Uvarint(s.mem[addr+n : fieldsIndexEnd])
n += uint64(read)
name := string(s.mem[addr+n : addr+n+nameLen])
s.fieldsInv = append(s.fieldsInv, name)
s.fieldsMap[name] = uint16(fieldID + 1)
fieldID++
}
return nil
}
// Dictionary returns the term dictionary for the specified field
func (s *SegmentBase) Dictionary(field string) (segment.TermDictionary, error) {
dict, err := s.dictionary(field)
if err == nil && dict == nil {
return &segment.EmptyDictionary{}, nil
}
return dict, err
}
func (sb *SegmentBase) dictionary(field string) (rv *Dictionary, err error) {
fieldIDPlus1 := sb.fieldsMap[field]
if fieldIDPlus1 > 0 {
rv = &Dictionary{
sb: sb,
field: field,
fieldID: fieldIDPlus1 - 1,
}
dictStart := sb.dictLocs[rv.fieldID]
if dictStart > 0 {
// read the length of the vellum data
vellumLen, read := binary.Uvarint(sb.mem[dictStart : dictStart+binary.MaxVarintLen64])
fstBytes := sb.mem[dictStart+uint64(read) : dictStart+uint64(read)+vellumLen]
if fstBytes != nil {
rv.fst, err = vellum.Load(fstBytes)
if err != nil {
return nil, fmt.Errorf("dictionary field %s vellum err: %v", field, err)
}
}
}
}
return rv, nil
}
// VisitDocument invokes the DocFieldValueVistor for each stored field
// for the specified doc number
func (s *SegmentBase) VisitDocument(num uint64, visitor segment.DocumentFieldValueVisitor) error {
// first make sure this is a valid number in this segment
if num < s.numDocs {
meta, compressed := s.getDocStoredMetaAndCompressed(num)
uncompressed, err := snappy.Decode(nil, compressed)
if err != nil {
return err
}
// now decode meta and process
reader := bytes.NewReader(meta)
decoder := govarint.NewU64Base128Decoder(reader)
keepGoing := true
for keepGoing {
field, err := decoder.GetU64()
if err == io.EOF {
break
}
if err != nil {
return err
}
typ, err := decoder.GetU64()
if err != nil {
return err
}
offset, err := decoder.GetU64()
if err != nil {
return err
}
l, err := decoder.GetU64()
if err != nil {
return err
}
numap, err := decoder.GetU64()
if err != nil {
return err
}
var arrayPos []uint64
if numap > 0 {
arrayPos = make([]uint64, numap)
for i := 0; i < int(numap); i++ {
ap, err := decoder.GetU64()
if err != nil {
return err
}
arrayPos[i] = ap
}
}
value := uncompressed[offset : offset+l]
keepGoing = visitor(s.fieldsInv[field], byte(typ), value, arrayPos)
}
}
return nil
}
// Count returns the number of documents in this segment.
func (s *SegmentBase) Count() uint64 {
return s.numDocs
}
// DocNumbers returns a bitset corresponding to the doc numbers of all the
// provided _id strings
func (s *SegmentBase) DocNumbers(ids []string) (*roaring.Bitmap, error) {
rv := roaring.New()
if len(s.fieldsMap) > 0 {
idDict, err := s.dictionary("_id")
if err != nil {
return nil, err
}
var postings *PostingsList
for _, id := range ids {
postings, err = idDict.postingsList([]byte(id), nil, postings)
if err != nil {
return nil, err
}
if postings.postings != nil {
rv.Or(postings.postings)
}
}
}
return rv, nil
}
// Fields returns the field names used in this segment
func (s *SegmentBase) Fields() []string {
return s.fieldsInv
}
// Path returns the path of this segment on disk
func (s *Segment) Path() string {
return s.path
}
// Close releases all resources associated with this segment
func (s *Segment) Close() (err error) {
return s.DecRef()
}
func (s *Segment) closeActual() (err error) {
if s.mm != nil {
err = s.mm.Unmap()
}
// try to close file even if unmap failed
if s.f != nil {
err2 := s.f.Close()
if err == nil {
// try to return first error
err = err2
}
}
return
}
// some helpers i started adding for the command-line utility
// Data returns the underlying mmaped data slice
func (s *Segment) Data() []byte {
return s.mm
}
// CRC returns the CRC value stored in the file footer
func (s *Segment) CRC() uint32 {
return s.crc
}
// Version returns the file version in the file footer
func (s *Segment) Version() uint32 {
return s.version
}
// ChunkFactor returns the chunk factor in the file footer
func (s *Segment) ChunkFactor() uint32 {
return s.chunkFactor
}
// FieldsIndexOffset returns the fields index offset in the file footer
func (s *Segment) FieldsIndexOffset() uint64 {
return s.fieldsIndexOffset
}
// StoredIndexOffset returns the stored value index offset in the file footer
func (s *Segment) StoredIndexOffset() uint64 {
return s.storedIndexOffset
}
// DocValueOffset returns the docValue offset in the file footer
func (s *Segment) DocValueOffset() uint64 {
return s.docValueOffset
}
// NumDocs returns the number of documents in the file footer
func (s *Segment) NumDocs() uint64 {
return s.numDocs
}
// DictAddr is a helper function to compute the file offset where the
// dictionary is stored for the specified field.
func (s *Segment) DictAddr(field string) (uint64, error) {
fieldIDPlus1, ok := s.fieldsMap[field]
if !ok {
return 0, fmt.Errorf("no such field '%s'", field)
}
return s.dictLocs[fieldIDPlus1-1], nil
}
func (s *SegmentBase) loadDvIterators() error {
if s.docValueOffset == fieldNotUninverted {
return nil
}
var read uint64
for fieldID, field := range s.fieldsInv {
fieldLoc, n := binary.Uvarint(s.mem[s.docValueOffset+read : s.docValueOffset+read+binary.MaxVarintLen64])
if n <= 0 {
return fmt.Errorf("loadDvIterators: failed to read the docvalue offsets for field %d", fieldID)
}
s.fieldDvIterMap[uint16(fieldID)], _ = s.loadFieldDocValueIterator(field, fieldLoc)
read += uint64(n)
}
return nil
}