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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
- }
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