add decode kvsdb tool (#2059)

* add decode kvsdb tool

* style: Format code with prettier and gofumpt

* add csv header

* modify to strings.Builder

* style: Format code with prettier and gofumpt

* modify to encoding/csv

* add error check

---------

Co-authored-by: deepsource-autofix[bot] <62050782+deepsource-autofix[bot]@users.noreply.github.com>

hack/tools/kvsdb/main.go

@@ -0,0 +1,106 @@
+//
+// Copyright (C) 2019-2023 vdaas.org vald team <[email protected]>
+//
+// 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
+//
+//    https://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 main
+
+import (
+	"encoding/csv"
+	"encoding/gob"
+	"flag"
+	"io/fs"
+	"os"
+	"strconv"
+	"unsafe"
+
+	"github.com/vdaas/vald/internal/file"
+	"github.com/vdaas/vald/internal/log"
+)
+
+var (
+	format               = flag.String("format", "csv", "file format(csv,tsv)")
+	kvsFileName          = flag.String("file", "ngt-meta.kvsdb", "kvsdb file name")
+	kvsTimestampFileName = flag.String("timestamp-file", "ngt-timestamp.kvsdb", "kvsdb timestamp file name")
+	path                 = flag.String("path", ".", "kvsdb file path")
+)
+
+func main() {
+	flag.Parse()
+	log.Init()
+	var err error
+
+	// value
+	m := make(map[string]uint32)
+	gob.Register(map[string]uint32{})
+	var f *os.File
+	defer f.Close()
+	f, err = file.Open(
+		file.Join(*path, *kvsFileName),
+		os.O_RDONLY|os.O_SYNC,
+		fs.ModePerm,
+	)
+	if err != nil {
+		log.Fatal(err)
+	}
+	if err = gob.NewDecoder(f).Decode(&m); err != nil {
+		log.Fatal(err)
+	}
+
+	// timestamp
+	mt := make(map[string]int64)
+	gob.Register(map[string]int64{})
+	var ft *os.File
+	defer ft.Close()
+	ft, err = file.Open(
+		file.Join(*path, *kvsTimestampFileName),
+		os.O_RDONLY|os.O_SYNC,
+		fs.ModePerm,
+	)
+	if err != nil {
+		log.Fatal(err)
+	}
+	if err = gob.NewDecoder(ft).Decode(&mt); err != nil {
+		log.Fatal(err)
+	}
+
+	// print
+	var s [][]string
+	w := csv.NewWriter(os.Stdout)
+	defer w.Flush()
+	switch *format {
+	case "csv":
+	case "tsv":
+		w.Comma = '\t'
+	default:
+		w.Comma = ' '
+	}
+	s = append(s, []string{"uuid", "oid", "timestamp"})
+	for k, id := range m {
+		if ts, ok := mt[k]; ok {
+			s = append(s, []string{k, strconv.FormatUint(uint64(id), 10), strconv.FormatInt(ts, 10)})
+		} else {
+			s = append(s, []string{k, strconv.FormatUint(uint64(id), 10), "0"})
+		}
+		if len(s)*int(unsafe.Sizeof("")) > 4e+6 {
+			if err = w.WriteAll(s); err != nil {
+				log.Fatal(err)
+			}
+			s = nil
+		}
+	}
+	if err = w.WriteAll(s); err != nil {
+		log.Fatal(err)
+	}
+}