first-commit

modules/indexer/internal/bleve/util.go

@@ -0,0 +1,90 @@
+// 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)
+}