158 lines
4 KiB
Go
Vendored
158 lines
4 KiB
Go
Vendored
// 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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"fmt"
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"github.com/RoaringBitmap/roaring"
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index "github.com/blevesearch/bleve_index_api"
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segment "github.com/blevesearch/scorch_segment_api/v2"
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"github.com/blevesearch/vellum"
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)
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// Dictionary is the zap representation of the term dictionary
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type Dictionary struct {
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sb *SegmentBase
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field string
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fieldID uint16
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fst *vellum.FST
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fstReader *vellum.Reader
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}
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// represents an immutable, empty dictionary
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var emptyDictionary = &Dictionary{}
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// PostingsList returns the postings list for the specified term
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func (d *Dictionary) PostingsList(term []byte, except *roaring.Bitmap,
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prealloc segment.PostingsList) (segment.PostingsList, error) {
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var preallocPL *PostingsList
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pl, ok := prealloc.(*PostingsList)
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if ok && pl != nil {
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preallocPL = pl
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}
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return d.postingsList(term, except, preallocPL)
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}
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func (d *Dictionary) postingsList(term []byte, except *roaring.Bitmap, rv *PostingsList) (*PostingsList, error) {
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if d.fstReader == nil {
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if rv == nil || rv == emptyPostingsList {
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return emptyPostingsList, nil
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}
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return d.postingsListInit(rv, except), nil
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}
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postingsOffset, exists, err := d.fstReader.Get(term)
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if err != nil {
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return nil, fmt.Errorf("vellum err: %v", err)
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}
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if !exists {
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if rv == nil || rv == emptyPostingsList {
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return emptyPostingsList, nil
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}
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return d.postingsListInit(rv, except), nil
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}
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return d.postingsListFromOffset(postingsOffset, except, rv)
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}
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func (d *Dictionary) postingsListFromOffset(postingsOffset uint64, except *roaring.Bitmap, rv *PostingsList) (*PostingsList, error) {
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rv = d.postingsListInit(rv, except)
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err := rv.read(postingsOffset, d)
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if err != nil {
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return nil, err
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}
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return rv, nil
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}
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func (d *Dictionary) postingsListInit(rv *PostingsList, except *roaring.Bitmap) *PostingsList {
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if rv == nil || rv == emptyPostingsList {
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rv = &PostingsList{}
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} else {
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postings := rv.postings
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if postings != nil {
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postings.Clear()
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}
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*rv = PostingsList{} // clear the struct
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rv.postings = postings
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}
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rv.sb = d.sb
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rv.except = except
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return rv
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}
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func (d *Dictionary) Contains(key []byte) (bool, error) {
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if d.fst != nil {
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return d.fst.Contains(key)
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}
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return false, nil
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}
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// AutomatonIterator returns an iterator which only visits terms
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// having the the vellum automaton and start/end key range
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func (d *Dictionary) AutomatonIterator(a segment.Automaton,
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startKeyInclusive, endKeyExclusive []byte) segment.DictionaryIterator {
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if d.fst != nil {
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rv := &DictionaryIterator{
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d: d,
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}
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itr, err := d.fst.Search(a, startKeyInclusive, endKeyExclusive)
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if err == nil {
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rv.itr = itr
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} else if err != vellum.ErrIteratorDone {
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rv.err = err
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}
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return rv
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}
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return emptyDictionaryIterator
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}
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// DictionaryIterator is an iterator for term dictionary
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type DictionaryIterator struct {
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d *Dictionary
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itr vellum.Iterator
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err error
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tmp PostingsList
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entry index.DictEntry
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omitCount bool
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}
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var emptyDictionaryIterator = &DictionaryIterator{}
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// Next returns the next entry in the dictionary
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func (i *DictionaryIterator) Next() (*index.DictEntry, error) {
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if i.err != nil && i.err != vellum.ErrIteratorDone {
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return nil, i.err
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} else if i.itr == nil || i.err == vellum.ErrIteratorDone {
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return nil, nil
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}
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term, postingsOffset := i.itr.Current()
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i.entry.Term = string(term)
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if !i.omitCount {
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i.err = i.tmp.read(postingsOffset, i.d)
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if i.err != nil {
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return nil, i.err
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}
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i.entry.Count = i.tmp.Count()
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}
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i.err = i.itr.Next()
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return &i.entry, nil
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}
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