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dict.go
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/
dict.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 (
"encoding/binary"
"fmt"
"github.com/RoaringBitmap/roaring"
"github.com/blevesearch/bleve/index"
"github.com/blevesearch/bleve/index/scorch/segment"
"github.com/couchbase/vellum"
"github.com/couchbase/vellum/regexp"
)
// Dictionary is the zap representation of the term dictionary
type Dictionary struct {
segment *Segment
field string
fieldID uint16
fst *vellum.FST
}
// PostingsList returns the postings list for the specified term
func (d *Dictionary) PostingsList(term string, except *roaring.Bitmap) (segment.PostingsList, error) {
return d.postingsList(term, except)
}
func (d *Dictionary) postingsList(term string, except *roaring.Bitmap) (*PostingsList, error) {
rv := &PostingsList{
dictionary: d,
term: term,
except: except,
}
if d.fst != nil {
postingsOffset, exists, err := d.fst.Get([]byte(term))
if err != nil {
return nil, fmt.Errorf("vellum err: %v", err)
}
if exists {
rv.postingsOffset = postingsOffset
// read the location of the freq/norm details
var n uint64
var read int
rv.freqOffset, read = binary.Uvarint(d.segment.mm[postingsOffset+n : postingsOffset+binary.MaxVarintLen64])
n += uint64(read)
rv.locOffset, read = binary.Uvarint(d.segment.mm[postingsOffset+n : postingsOffset+n+binary.MaxVarintLen64])
n += uint64(read)
var locBitmapOffset uint64
locBitmapOffset, read = binary.Uvarint(d.segment.mm[postingsOffset+n : postingsOffset+n+binary.MaxVarintLen64])
n += uint64(read)
// go ahead and load loc bitmap
var locBitmapLen uint64
locBitmapLen, read = binary.Uvarint(d.segment.mm[locBitmapOffset : locBitmapOffset+binary.MaxVarintLen64])
locRoaringBytes := d.segment.mm[locBitmapOffset+uint64(read) : locBitmapOffset+uint64(read)+locBitmapLen]
rv.locBitmap = roaring.NewBitmap()
_, err := rv.locBitmap.FromBuffer(locRoaringBytes)
if err != nil {
return nil, fmt.Errorf("error loading roaring bitmap of locations with hits: %v", err)
}
var postingsLen uint64
postingsLen, read = binary.Uvarint(d.segment.mm[postingsOffset+n : postingsOffset+n+binary.MaxVarintLen64])
n += uint64(read)
roaringBytes := d.segment.mm[postingsOffset+n : postingsOffset+n+postingsLen]
bitmap := roaring.NewBitmap()
_, err = bitmap.FromBuffer(roaringBytes)
if err != nil {
return nil, fmt.Errorf("error loading roaring bitmap: %v", err)
}
rv.postings = bitmap
}
}
return rv, nil
}
// Iterator returns an iterator for this dictionary
func (d *Dictionary) Iterator() segment.DictionaryIterator {
rv := &DictionaryIterator{
d: d,
}
if d.fst != nil {
itr, err := d.fst.Iterator(nil, nil)
if err == nil {
rv.itr = itr
}
}
return rv
}
// PrefixIterator returns an iterator which only visits terms having the
// the specified prefix
func (d *Dictionary) PrefixIterator(prefix string) segment.DictionaryIterator {
rv := &DictionaryIterator{
d: d,
}
if d.fst != nil {
r, err := regexp.New(prefix + ".*")
if err == nil {
itr, err := d.fst.Search(r, nil, nil)
if err == nil {
rv.itr = itr
}
}
}
return rv
}
// RangeIterator returns an iterator which only visits terms between the
// start and end terms. NOTE: bleve.index API specifies the end is inclusive.
func (d *Dictionary) RangeIterator(start, end string) segment.DictionaryIterator {
rv := &DictionaryIterator{
d: d,
}
// need to increment the end position to be inclusive
endBytes := []byte(end)
if endBytes[len(endBytes)-1] < 0xff {
endBytes[len(endBytes)-1]++
} else {
endBytes = append(endBytes, 0xff)
}
if d.fst != nil {
itr, err := d.fst.Iterator([]byte(start), endBytes)
if err == nil {
rv.itr = itr
}
}
return rv
}
// DictionaryIterator is an iterator for term dictionary
type DictionaryIterator struct {
d *Dictionary
itr vellum.Iterator
err error
}
// Next returns the next entry in the dictionary
func (i *DictionaryIterator) Next() (*index.DictEntry, error) {
if i.itr == nil || i.err == vellum.ErrIteratorDone {
return nil, nil
} else if i.err != nil {
return nil, i.err
}
term, count := i.itr.Current()
rv := &index.DictEntry{
Term: string(term),
Count: count,
}
i.err = i.itr.Next()
return rv, nil
}