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field_reader.go
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/
field_reader.go
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// Copyright (c) 2014 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 upside_down
import (
"bytes"
"fmt"
"github.com/blevesearch/bleve/index"
"github.com/blevesearch/bleve/index/store"
)
type UpsideDownCouchFieldReader struct {
indexReader *IndexReader
iterator store.KVIterator
endKey []byte
field uint16
}
func newUpsideDownCouchFieldReader(indexReader *IndexReader, field uint16, startTerm, endTerm []byte) (*UpsideDownCouchFieldReader, error) {
startRow := NewTermFrequencyRow(startTerm, field, "", 0, 0)
startKey := startRow.ScanPrefixForFieldTermPrefix()
endKey := NewTermFrequencyRow(endTerm, field, "", 0, 0).Key()
it := indexReader.kvreader.Iterator(startKey)
return &UpsideDownCouchFieldReader{
indexReader: indexReader,
iterator: it,
field: field,
endKey: endKey,
}, nil
}
func (r *UpsideDownCouchFieldReader) Next() (*index.TermFieldDoc, error) {
key, val, valid := r.iterator.Current()
if !valid {
return nil, nil
}
// past end term
if bytes.Compare(key, r.endKey) > 0 {
return nil, nil
}
currRow, err := NewTermFrequencyRowKV(key, val)
if err != nil {
return nil, fmt.Errorf("unexpected error parsing term freq row kv: %v", err)
}
rv := index.TermFieldDoc{
Term: string(currRow.term),
Freq: currRow.freq,
}
// advance the iterator to the next term
// by using invalid doc id (higher sorting)
nextTerm := incrementBytes(currRow.term)
nextRow := NewTermFrequencyRow(nextTerm, r.field, "", 0, 0)
r.iterator.Seek(nextRow.ScanPrefixForFieldTermPrefix())
return &rv, nil
}
func (r *UpsideDownCouchFieldReader) Close() {
r.iterator.Close()
}
func incrementBytes(in []byte) []byte {
rv := make([]byte, len(in))
copy(rv, in)
for i := len(rv) - 1; i >= 0; i-- {
rv[i] = rv[i] + 1
if rv[i] != 0 {
// didnt' overflow, so stop
break
}
}
return rv
}