forked from blevesearch/bleve
/
dict.go
165 lines (141 loc) · 3.95 KB
/
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 (
"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 {
sb *SegmentBase
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([]byte(term), except, nil)
}
func (d *Dictionary) postingsList(term []byte, except *roaring.Bitmap, rv *PostingsList) (*PostingsList, error) {
if d.fst == nil {
return d.postingsListInit(rv, except), nil
}
postingsOffset, exists, err := d.fst.Get(term)
if err != nil {
return nil, fmt.Errorf("vellum err: %v", err)
}
if !exists {
return d.postingsListInit(rv, except), nil
}
return d.postingsListFromOffset(postingsOffset, except, rv)
}
func (d *Dictionary) postingsListFromOffset(postingsOffset uint64, except *roaring.Bitmap, rv *PostingsList) (*PostingsList, error) {
rv = d.postingsListInit(rv, except)
err := rv.read(postingsOffset, d)
if err != nil {
return nil, err
}
return rv, nil
}
func (d *Dictionary) postingsListInit(rv *PostingsList, except *roaring.Bitmap) *PostingsList {
if rv == nil {
rv = &PostingsList{}
} else {
*rv = PostingsList{} // clear the struct
}
rv.sb = d.sb
rv.except = except
return rv
}
// 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
tmp PostingsList
}
// 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, postingsOffset := i.itr.Current()
i.err = i.tmp.read(postingsOffset, i.d)
if i.err != nil {
return nil, i.err
}
rv := &index.DictEntry{
Term: string(term),
Count: i.tmp.Count(),
}
i.err = i.itr.Next()
return rv, nil
}