feat: add --max-levels (with validation) to root command and --memtable-size to info command CLI flags

badger/cmd/backup.go

@@ -44,7 +44,8 @@ func init() {
 func doBackup(cmd *cobra.Command, args []string) error {
 	opt := badger.DefaultOptions(sstDir).
 		WithValueDir(vlogDir).
-		WithNumVersionsToKeep(math.MaxInt32)
+		WithNumVersionsToKeep(math.MaxInt32).
+		WithMaxLevels(vMaxLevels)
 
 	if bo.numVersions > 0 {
 		opt.NumVersionsToKeep = bo.numVersions

badger/cmd/bank.go

@@ -303,7 +303,8 @@ func runDisect(cmd *cobra.Command, args []string) error {
 		WithValueDir(vlogDir).
 		WithReadOnly(true).
 		WithEncryptionKey([]byte(encryptionKey)).
-		WithIndexCacheSize(1 << 30))
+		WithIndexCacheSize(1 << 30).
+		WithMaxLevels(vMaxLevels))
 	if err != nil {
 		return err
 	}
@@ -351,7 +352,8 @@ func runTest(cmd *cobra.Command, args []string) error {
 		// Do not GC any versions, because we need them for the disect.
 		WithNumVersionsToKeep(int(math.MaxInt32)).
 		WithBlockCacheSize(1 << 30).
-		WithIndexCacheSize(1 << 30)
+		WithIndexCacheSize(1 << 30).
+		WithMaxLevels(vMaxLevels)
 
 	if verbose {
 		opts = opts.WithLoggingLevel(badger.DEBUG)
@@ -376,7 +378,7 @@ func runTest(cmd *cobra.Command, args []string) error {
 		dir, err := os.MkdirTemp("", "bank_subscribe")
 		y.Check(err)
 
-		subscribeDB, err = badger.Open(badger.DefaultOptions(dir).WithSyncWrites(false))
+		subscribeDB, err = badger.Open(badger.DefaultOptions(dir).WithSyncWrites(false).WithMaxLevels(vMaxLevels))
 		if err != nil {
 			return err
 		}
@@ -387,7 +389,7 @@ func runTest(cmd *cobra.Command, args []string) error {
 		dir, err := os.MkdirTemp("", "bank_stream")
 		y.Check(err)
 
-		tmpDb, err = badger.Open(badger.DefaultOptions(dir).WithSyncWrites(false))
+		tmpDb, err = badger.Open(badger.DefaultOptions(dir).WithSyncWrites(false).WithMaxLevels(vMaxLevels))
 		if err != nil {
 			return err
 		}

badger/cmd/cli_test.go

@@ -0,0 +1,66 @@
+/*
+ * SPDX-FileCopyrightText: © 2017-2025 Istari Digital, Inc.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package cmd
+
+import (
+	"os"
+	"testing"
+
+	"github.com/spf13/cobra"
+	"github.com/stretchr/testify/require"
+
+	"github.com/dgraph-io/badger/v4"
+)
+
+// TestMaxLevelsFlag tests the --max-levels CLI flag
+func TestMaxLevelsFlag(t *testing.T) {
+	tests := []struct {
+		name        string
+		maxLevels   int
+		shouldError bool
+	}{
+		{"max-levels-0", 0, true},
+		{"max-levels-negative", -1, true},
+		{"max-levels-10", 10, false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			dir, err := os.MkdirTemp("", "badger-max-levels-test")
+			require.NoError(t, err)
+			defer func() {
+				if err := os.RemoveAll(dir); err != nil {
+					t.Fatalf("Failed to clean up temp directory: %v", err)
+				}
+			}()
+
+			// Set the vMaxLevels variable to test value
+			oldMaxLevels := vMaxLevels
+			vMaxLevels = tt.maxLevels
+			defer func() { vMaxLevels = oldMaxLevels }()
+
+			sstDir = dir
+			vlogDir = dir
+
+			// Test validation - create a mock cobra command to avoid nil pointer dereference
+			cmd := &cobra.Command{Use: "test"}
+			err = validateRootCmdArgs(cmd, []string{})
+
+			if tt.shouldError {
+				require.Error(t, err, "Expected validation to fail for max-levels=%d", tt.maxLevels)
+				require.Contains(t, err.Error(), "--max-levels should be at least 1")
+			} else {
+				require.NoError(t, err, "Expected validation to pass for max-levels=%d", tt.maxLevels)
+
+				// Test that DB can be opened with the max-levels setting
+				opts := badger.DefaultOptions(dir).WithMaxLevels(vMaxLevels)
+				db, err := badger.Open(opts)
+				require.NoError(t, err)
+				require.NoError(t, db.Close())
+			}
+		})
+	}
+}

badger/cmd/flatten.go

@@ -67,7 +67,8 @@ func flatten(cmd *cobra.Command, args []string) error {
 		WithBlockCacheSize(100 << 20).
 		WithIndexCacheSize(200 << 20).
 		WithCompression(options.CompressionType(fo.compressionType)).
-		WithEncryptionKey(encKey)
+		WithEncryptionKey(encKey).
+		WithMaxLevels(vMaxLevels)
 	fmt.Printf("Opening badger with options = %+v\n", opt)
 	db, err := badger.Open(opt)
 	if err != nil {

badger/cmd/info.go

@@ -40,6 +40,8 @@ type flagOptions struct {
 	checksumVerificationMode string
 	discard                  bool
 	externalMagicVersion     uint16
+
+	memTableSize int64
 }
 
 var (
@@ -73,6 +75,8 @@ func init() {
 		"Parse and print DISCARD file from value logs.")
 	infoCmd.Flags().Uint16Var(&opt.externalMagicVersion, "external-magic", 0,
 		"External magic number")
+	infoCmd.Flags().Int64Var(&opt.memTableSize, "memtable-size", 128<<20,
+		"Size of memtable in bytes.")
 }
 
 var infoCmd = &cobra.Command{
@@ -96,7 +100,9 @@ func handleInfo(cmd *cobra.Command, args []string) error {
 		WithIndexCacheSize(200 << 20).
 		WithEncryptionKey([]byte(opt.encryptionKey)).
 		WithChecksumVerificationMode(cvMode).
-		WithExternalMagic(opt.externalMagicVersion)
+		WithExternalMagic(opt.externalMagicVersion).
+		WithMemTableSize(opt.memTableSize).
+		WithMaxLevels(vMaxLevels)
 
 	if opt.discard {
 		ds, err := badger.InitDiscardStats(bopt)

badger/cmd/pick_table_bench.go

@@ -51,7 +51,8 @@ func init() {
 func pickTableBench(cmd *cobra.Command, args []string) error {
 	opt := badger.DefaultOptions(sstDir).
 		WithValueDir(vlogDir).
-		WithReadOnly(pickOpts.readOnly)
+		WithReadOnly(pickOpts.readOnly).
+		WithMaxLevels(vMaxLevels)
 	fmt.Printf("Opening badger with options = %+v\n", opt)
 	db, err := badger.OpenManaged(opt)
 	if err != nil {

badger/cmd/read_bench.go

@@ -98,7 +98,8 @@ func readBench(cmd *cobra.Command, args []string) error {
 		WithValueDir(vlogDir).
 		WithReadOnly(ro.readOnly).
 		WithBlockCacheSize(ro.blockCacheSize << 20).
-		WithIndexCacheSize(ro.indexCacheSize << 20)
+		WithIndexCacheSize(ro.indexCacheSize << 20).
+		WithMaxLevels(vMaxLevels)
 	fmt.Printf("Opening badger with options = %+v\n", opt)
 	db, err := badger.OpenManaged(opt)
 	if err != nil {

badger/cmd/restore.go

@@ -58,7 +58,8 @@ func doRestore(cmd *cobra.Command, args []string) error {
 	// Open DB
 	db, err := badger.Open(badger.DefaultOptions(sstDir).
 		WithValueDir(vlogDir).
-		WithNumVersionsToKeep(math.MaxInt32))
+		WithNumVersionsToKeep(math.MaxInt32).
+		WithMaxLevels(vMaxLevels))
 	if err != nil {
 		return err
 	}

badger/cmd/root.go

@@ -16,6 +16,8 @@ import (
 
 var sstDir, vlogDir string
 
+var vMaxLevels int
+
 // RootCmd represents the base command when called without any subcommands
 var RootCmd = &cobra.Command{
 	Use:               "badger",
@@ -38,6 +40,9 @@ func init() {
 
 	RootCmd.PersistentFlags().StringVar(&vlogDir, "vlog-dir", "",
 		"Directory where the value log files are located, if different from --dir")
+
+	RootCmd.PersistentFlags().IntVar(&vMaxLevels, "max-levels", 7,
+		"Maximum number of levels in the LSM tree")
 }
 
 func validateRootCmdArgs(cmd *cobra.Command, args []string) error {
@@ -50,5 +55,9 @@ func validateRootCmdArgs(cmd *cobra.Command, args []string) error {
 	if vlogDir == "" {
 		vlogDir = sstDir
 	}
+
+	if vMaxLevels < 1 {
+		return errors.New("--max-levels should be at least 1")
+	}
 	return nil
 }

badger/cmd/stream.go

@@ -71,7 +71,8 @@ func stream(cmd *cobra.Command, args []string) error {
 		WithNumVersionsToKeep(so.numVersions).
 		WithBlockCacheSize(100 << 20).
 		WithIndexCacheSize(200 << 20).
-		WithEncryptionKey(encKey)
+		WithEncryptionKey(encKey).
+		WithMaxLevels(vMaxLevels)
 
 	// Options for output DB.
 	if so.compressionType > 2 {

badger/cmd/write_bench.go

@@ -264,7 +264,8 @@ func writeBench(cmd *cobra.Command, args []string) error {
 		WithValueLogMaxEntries(wo.vlogMaxEntries).
 		WithEncryptionKey([]byte(wo.encryptionKey)).
 		WithDetectConflicts(wo.detectConflicts).
-		WithLoggingLevel(badger.INFO)
+		WithLoggingLevel(badger.INFO).
+		WithMaxLevels(vMaxLevels)
 	if wo.zstdComp {
 		opt = opt.WithCompression(options.ZSTD)
 	}

levels.go

@@ -1477,7 +1477,7 @@ func (s *levelsController) runCompactDef(id, l int, cd compactDef) (err error) {
 			expensive = " [E]"
 		}
 		s.kv.opt.Infof("[%d]%s LOG Compact %d->%d (%d, %d -> %d tables with %d splits)."+
-			" [%s] -> [%s], took %v\n, deleted %d bytes",
+			" [%s] -> [%s], took %v, deleted %d bytes\n",
 			id, expensive, thisLevel.level, nextLevel.level, len(cd.top), len(cd.bot),
 			len(newTables), len(cd.splits), strings.Join(from, " "), strings.Join(to, " "),
 			dur.Round(time.Millisecond), sizeOldTables-sizeNewTables)