- // 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"
- index "github.com/blevesearch/bleve_index_api"
- segment "github.com/blevesearch/scorch_segment_api/v2"
- "github.com/blevesearch/vellum"
- )
-
- // Dictionary is the zap representation of the term dictionary
- type Dictionary struct {
- sb *SegmentBase
- field string
- fieldID uint16
- fst *vellum.FST
- fstReader *vellum.Reader
- }
-
- // represents an immutable, empty dictionary
- var emptyDictionary = &Dictionary{}
-
- // PostingsList returns the postings list for the specified term
- func (d *Dictionary) PostingsList(term []byte, except *roaring.Bitmap,
- prealloc segment.PostingsList) (segment.PostingsList, error) {
- var preallocPL *PostingsList
- pl, ok := prealloc.(*PostingsList)
- if ok && pl != nil {
- preallocPL = pl
- }
- return d.postingsList(term, except, preallocPL)
- }
-
- func (d *Dictionary) postingsList(term []byte, except *roaring.Bitmap, rv *PostingsList) (*PostingsList, error) {
- if d.fstReader == nil {
- if rv == nil || rv == emptyPostingsList {
- return emptyPostingsList, nil
- }
- return d.postingsListInit(rv, except), nil
- }
-
- postingsOffset, exists, err := d.fstReader.Get(term)
- if err != nil {
- return nil, fmt.Errorf("vellum err: %v", err)
- }
- if !exists {
- if rv == nil || rv == emptyPostingsList {
- return emptyPostingsList, nil
- }
- 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 == emptyPostingsList {
- rv = &PostingsList{}
- } else {
- postings := rv.postings
- if postings != nil {
- postings.Clear()
- }
-
- *rv = PostingsList{} // clear the struct
-
- rv.postings = postings
- }
- rv.sb = d.sb
- rv.except = except
- return rv
- }
-
- func (d *Dictionary) Contains(key []byte) (bool, error) {
- if d.fst != nil {
- return d.fst.Contains(key)
- }
- return false, nil
- }
-
- // AutomatonIterator returns an iterator which only visits terms
- // having the the vellum automaton and start/end key range
- func (d *Dictionary) AutomatonIterator(a segment.Automaton,
- startKeyInclusive, endKeyExclusive []byte) segment.DictionaryIterator {
- if d.fst != nil {
- rv := &DictionaryIterator{
- d: d,
- }
-
- itr, err := d.fst.Search(a, startKeyInclusive, endKeyExclusive)
- if err == nil {
- rv.itr = itr
- } else if err != vellum.ErrIteratorDone {
- rv.err = err
- }
-
- return rv
- }
- return emptyDictionaryIterator
- }
-
- // DictionaryIterator is an iterator for term dictionary
- type DictionaryIterator struct {
- d *Dictionary
- itr vellum.Iterator
- err error
- tmp PostingsList
- entry index.DictEntry
- omitCount bool
- }
-
- var emptyDictionaryIterator = &DictionaryIterator{}
-
- // Next returns the next entry in the dictionary
- func (i *DictionaryIterator) Next() (*index.DictEntry, error) {
- if i.err != nil && i.err != vellum.ErrIteratorDone {
- return nil, i.err
- } else if i.itr == nil || i.err == vellum.ErrIteratorDone {
- return nil, nil
- }
- term, postingsOffset := i.itr.Current()
- i.entry.Term = string(term)
- if !i.omitCount {
- i.err = i.tmp.read(postingsOffset, i.d)
- if i.err != nil {
- return nil, i.err
- }
- i.entry.Count = i.tmp.Count()
- }
- i.err = i.itr.Next()
- return &i.entry, nil
- }
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