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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"
index "github.com/blevesearch/bleve_index_api"
segment "github.com/blevesearch/scorch_segment_api"
"github.com/couchbase/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 vellum.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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