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// Copyright 2023 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT
package bleve
import (
"errors"
"os"
"unicode"
"code.gitea.io/gitea/modules/log"
"code.gitea.io/gitea/modules/setting"
"code.gitea.io/gitea/modules/util"
"github.com/blevesearch/bleve/v2"
unicode_tokenizer "github.com/blevesearch/bleve/v2/analysis/tokenizer/unicode"
"github.com/blevesearch/bleve/v2/index/upsidedown"
"github.com/ethantkoenig/rupture"
)
const (
maxFuzziness = 2
)
// openIndexer open the index at the specified path, checking for metadata
// updates and bleve version updates. If index needs to be created (or
// re-created), returns (nil, nil)
func openIndexer(path string, latestVersion int) (bleve.Index, int, error) {
_, err := os.Stat(path)
if err != nil && os.IsNotExist(err) {
return nil, 0, nil
} else if err != nil {
return nil, 0, err
}
metadata, err := rupture.ReadIndexMetadata(path)
if err != nil {
return nil, 0, err
}
if metadata.Version < latestVersion {
// the indexer is using a previous version, so we should delete it and
// re-populate
return nil, metadata.Version, util.RemoveAll(path)
}
index, err := bleve.Open(path)
if err != nil {
if errors.Is(err, upsidedown.IncompatibleVersion) {
log.Warn("Indexer was built with a previous version of bleve, deleting and rebuilding")
return nil, 0, util.RemoveAll(path)
}
return nil, 0, err
}
return index, 0, nil
}
// GuessFuzzinessByKeyword guesses fuzziness based on the levenshtein distance and determines how many chars
// may be different on two string, and they still be considered equivalent.
// Given a phrase, its shortest word determines its fuzziness. If a phrase uses CJK (eg: `갃갃갃` `啊啊啊`), the fuzziness is zero.
func GuessFuzzinessByKeyword(s string) int {
tokenizer := unicode_tokenizer.NewUnicodeTokenizer()
tokens := tokenizer.Tokenize([]byte(s))
if len(tokens) > 0 {
fuzziness := maxFuzziness
for _, token := range tokens {
fuzziness = min(fuzziness, guessFuzzinessByKeyword(string(token.Term)))
}
return fuzziness
}
return 0
}
func guessFuzzinessByKeyword(s string) int {
// according to https://github.com/blevesearch/bleve/issues/1563, the supported max fuzziness is 2
// magic number 4 was chosen to determine the levenshtein distance per each character of a keyword
// BUT, when using CJK (eg: `갃갃갃` `啊啊啊`), it mismatches a lot.
// Likewise, queries whose terms contains characters that are *not* letters should not use fuzziness
for _, r := range s {
if r >= 128 || !unicode.IsLetter(r) {
return 0
}
}
return min(min(setting.Indexer.TypeBleveMaxFuzzniess, maxFuzziness), len(s)/4)
}
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