422 lines
10 KiB
Go
422 lines
10 KiB
Go
// Copyright (c) 2017 Couchbase, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package zap
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import (
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"bufio"
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"bytes"
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"encoding/binary"
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"math"
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"os"
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"github.com/Smerity/govarint"
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"github.com/blevesearch/bleve/index/scorch/segment/mem"
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"github.com/couchbase/vellum"
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"github.com/golang/snappy"
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)
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const version uint32 = 1
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// PersistSegment takes the in-memory segment and persists it to the specified
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// path in the zap file format.
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func PersistSegment(memSegment *mem.Segment, path string, chunkFactor uint32) (err error) {
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flag := os.O_RDWR | os.O_CREATE
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f, err := os.OpenFile(path, flag, 0600)
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if err != nil {
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return err
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}
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// bufer the output
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br := bufio.NewWriter(f)
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// wrap it for counting (tracking offsets)
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cr := NewCountHashWriter(br)
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var storedIndexOffset uint64
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var dictLocs []uint64
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if len(memSegment.Stored) > 0 {
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storedIndexOffset, err = persistStored(memSegment, cr)
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if err != nil {
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return err
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}
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var freqOffsets, locOffsets []uint64
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freqOffsets, locOffsets, err = persistPostingDetails(memSegment, cr, chunkFactor)
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if err != nil {
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return err
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}
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var postingsListLocs []uint64
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postingsListLocs, err = persistPostingsLocs(memSegment, cr)
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if err != nil {
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return err
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}
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var postingsLocs []uint64
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postingsLocs, err = persistPostingsLists(memSegment, cr, postingsListLocs, freqOffsets, locOffsets)
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if err != nil {
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return err
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}
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dictLocs, err = persistDictionary(memSegment, cr, postingsLocs)
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if err != nil {
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return err
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}
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} else {
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dictLocs = make([]uint64, len(memSegment.FieldsInv))
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}
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var fieldIndexStart uint64
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fieldIndexStart, err = persistFields(memSegment.FieldsInv, cr, dictLocs)
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if err != nil {
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return err
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}
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err = persistFooter(uint64(len(memSegment.Stored)), storedIndexOffset,
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fieldIndexStart, chunkFactor, cr)
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if err != nil {
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return err
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}
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err = br.Flush()
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if err != nil {
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return err
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}
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err = f.Sync()
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if err != nil {
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return err
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}
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err = f.Close()
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if err != nil {
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return err
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}
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return nil
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}
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func persistStored(memSegment *mem.Segment, w *CountHashWriter) (uint64, error) {
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var curr int
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var metaBuf bytes.Buffer
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var data, compressed []byte
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docNumOffsets := make(map[int]uint64, len(memSegment.Stored))
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for docNum, storedValues := range memSegment.Stored {
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if docNum != 0 {
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// reset buffer if necessary
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metaBuf.Reset()
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data = data[:0]
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compressed = compressed[:0]
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curr = 0
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}
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metaEncoder := govarint.NewU64Base128Encoder(&metaBuf)
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// encode fields in order
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for fieldID := range memSegment.FieldsInv {
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if storedFieldValues, ok := storedValues[uint16(fieldID)]; ok {
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// has stored values for this field
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num := len(storedFieldValues)
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// process each value
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for i := 0; i < num; i++ {
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// encode field
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_, err2 := metaEncoder.PutU64(uint64(fieldID))
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if err2 != nil {
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return 0, err2
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}
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// encode type
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_, err2 = metaEncoder.PutU64(uint64(memSegment.StoredTypes[docNum][uint16(fieldID)][i]))
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if err2 != nil {
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return 0, err2
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}
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// encode start offset
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_, err2 = metaEncoder.PutU64(uint64(curr))
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if err2 != nil {
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return 0, err2
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}
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// end len
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_, err2 = metaEncoder.PutU64(uint64(len(storedFieldValues[i])))
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if err2 != nil {
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return 0, err2
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}
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// encode number of array pos
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_, err2 = metaEncoder.PutU64(uint64(len(memSegment.StoredPos[docNum][uint16(fieldID)][i])))
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if err2 != nil {
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return 0, err2
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}
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// encode all array positions
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for j := 0; j < len(memSegment.StoredPos[docNum][uint16(fieldID)][i]); j++ {
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_, err2 = metaEncoder.PutU64(memSegment.StoredPos[docNum][uint16(fieldID)][i][j])
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if err2 != nil {
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return 0, err2
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}
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}
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// append data
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data = append(data, storedFieldValues[i]...)
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// update curr
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curr += len(storedFieldValues[i])
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}
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}
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}
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metaEncoder.Close()
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metaBytes := metaBuf.Bytes()
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// compress the data
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compressed = snappy.Encode(compressed, data)
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// record where we're about to start writing
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docNumOffsets[docNum] = uint64(w.Count())
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// write out the meta len and compressed data len
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_, err := writeUvarints(w, uint64(len(metaBytes)), uint64(len(compressed)))
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if err != nil {
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return 0, err
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}
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// now write the meta
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_, err = w.Write(metaBytes)
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if err != nil {
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return 0, err
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}
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// now write the compressed data
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_, err = w.Write(compressed)
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if err != nil {
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return 0, err
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}
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}
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// return value is the start of the stored index
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rv := uint64(w.Count())
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// now write out the stored doc index
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for docNum := range memSegment.Stored {
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err := binary.Write(w, binary.BigEndian, docNumOffsets[docNum])
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if err != nil {
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return 0, err
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}
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}
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return rv, nil
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}
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func persistPostingDetails(memSegment *mem.Segment, w *CountHashWriter, chunkFactor uint32) ([]uint64, []uint64, error) {
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var freqOffsets, locOfffsets []uint64
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tfEncoder := newChunkedIntCoder(uint64(chunkFactor), uint64(len(memSegment.Stored)-1))
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for postingID := range memSegment.Postings {
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if postingID != 0 {
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tfEncoder.Reset()
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}
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postingsListItr := memSegment.Postings[postingID].Iterator()
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var offset int
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for postingsListItr.HasNext() {
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docNum := uint64(postingsListItr.Next())
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// put freq
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err := tfEncoder.Add(docNum, memSegment.Freqs[postingID][offset])
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if err != nil {
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return nil, nil, err
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}
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// put norm
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norm := memSegment.Norms[postingID][offset]
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normBits := math.Float32bits(norm)
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err = tfEncoder.Add(docNum, uint64(normBits))
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if err != nil {
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return nil, nil, err
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}
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offset++
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}
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// record where this postings freq info starts
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freqOffsets = append(freqOffsets, uint64(w.Count()))
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tfEncoder.Close()
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_, err := tfEncoder.Write(w)
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if err != nil {
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return nil, nil, err
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}
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}
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// now do it again for the locations
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locEncoder := newChunkedIntCoder(uint64(chunkFactor), uint64(len(memSegment.Stored)-1))
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for postingID := range memSegment.Postings {
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if postingID != 0 {
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locEncoder.Reset()
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}
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postingsListItr := memSegment.Postings[postingID].Iterator()
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var offset int
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var locOffset int
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for postingsListItr.HasNext() {
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docNum := uint64(postingsListItr.Next())
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for i := 0; i < int(memSegment.Freqs[postingID][offset]); i++ {
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if len(memSegment.Locfields[postingID]) > 0 {
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// put field
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err := locEncoder.Add(docNum, uint64(memSegment.Locfields[postingID][locOffset]))
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if err != nil {
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return nil, nil, err
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}
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// put pos
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err = locEncoder.Add(docNum, memSegment.Locpos[postingID][locOffset])
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if err != nil {
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return nil, nil, err
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}
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// put start
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err = locEncoder.Add(docNum, memSegment.Locstarts[postingID][locOffset])
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if err != nil {
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return nil, nil, err
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}
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// put end
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err = locEncoder.Add(docNum, memSegment.Locends[postingID][locOffset])
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if err != nil {
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return nil, nil, err
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}
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// put array positions
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num := len(memSegment.Locarraypos[postingID][locOffset])
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// put the number of array positions to follow
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err = locEncoder.Add(docNum, uint64(num))
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if err != nil {
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return nil, nil, err
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}
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// put each array position
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for j := 0; j < num; j++ {
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err = locEncoder.Add(docNum, memSegment.Locarraypos[postingID][locOffset][j])
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if err != nil {
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return nil, nil, err
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}
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}
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}
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locOffset++
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}
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offset++
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}
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// record where this postings loc info starts
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locOfffsets = append(locOfffsets, uint64(w.Count()))
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locEncoder.Close()
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_, err := locEncoder.Write(w)
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if err != nil {
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return nil, nil, err
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}
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}
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return freqOffsets, locOfffsets, nil
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}
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func persistPostingsLocs(memSegment *mem.Segment, w *CountHashWriter) (rv []uint64, err error) {
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for postingID := range memSegment.PostingsLocs {
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// record where we start this posting loc
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rv = append(rv, uint64(w.Count()))
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// write out the length and bitmap
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_, err = writeRoaringWithLen(memSegment.PostingsLocs[postingID], w)
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if err != nil {
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return nil, err
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}
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}
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return rv, nil
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}
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func persistPostingsLists(memSegment *mem.Segment, w *CountHashWriter,
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postingsListLocs, freqOffsets, locOffsets []uint64) (rv []uint64, err error) {
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for postingID := range memSegment.Postings {
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// record where we start this posting list
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rv = append(rv, uint64(w.Count()))
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// write out the term info, loc info, and loc posting list offset
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_, err = writeUvarints(w, freqOffsets[postingID],
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locOffsets[postingID], postingsListLocs[postingID])
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if err != nil {
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return nil, err
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}
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// write out the length and bitmap
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_, err = writeRoaringWithLen(memSegment.Postings[postingID], w)
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if err != nil {
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return nil, err
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}
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}
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return rv, nil
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}
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func persistDictionary(memSegment *mem.Segment, w *CountHashWriter, postingsLocs []uint64) ([]uint64, error) {
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var rv []uint64
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var buffer bytes.Buffer
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for fieldID, fieldTerms := range memSegment.DictKeys {
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if fieldID != 0 {
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buffer.Reset()
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}
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// start a new vellum for this field
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builder, err := vellum.New(&buffer, nil)
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if err != nil {
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return nil, err
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}
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dict := memSegment.Dicts[fieldID]
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// now walk the dictionary in order of fieldTerms (already sorted)
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for i := range fieldTerms {
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postingID := dict[fieldTerms[i]] - 1
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postingsAddr := postingsLocs[postingID]
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err = builder.Insert([]byte(fieldTerms[i]), postingsAddr)
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if err != nil {
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return nil, err
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}
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}
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err = builder.Close()
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if err != nil {
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return nil, err
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}
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// record where this dictionary starts
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rv = append(rv, uint64(w.Count()))
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vellumData := buffer.Bytes()
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// write out the length of the vellum data
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buf := make([]byte, binary.MaxVarintLen64)
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// write out the number of chunks
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n := binary.PutUvarint(buf, uint64(len(vellumData)))
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_, err = w.Write(buf[:n])
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if err != nil {
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return nil, err
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}
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// write this vellum to disk
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_, err = w.Write(vellumData)
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if err != nil {
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return nil, err
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}
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}
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return rv, nil
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}
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