resolve some minor review comments

Signed-off-by: Benjamin Wang <wachao@vmware.com>

cmd/bbolt/command_surgery_cobra.go

@@ -31,8 +31,8 @@ func newSurgeryCobraCommand() *cobra.Command {
 
 func newSurgeryClearPageElementsCommand() *cobra.Command {
 	clearElementCmd := &cobra.Command{
-		Use:   "clear-page-elements [options]",
-		Short: "Clears elements from the given page",
+		Use:   "clear-page-elements <bbolt-file> [options]",
+		Short: "Clears elements from the given page, which can be a branch or leaf page",
 		Args: func(cmd *cobra.Command, args []string) error {
 			if len(args) == 0 {
 				return errors.New("db file path not provided")

cmd/bbolt/command_surgery_cobra_test.go

@@ -2,7 +2,6 @@ package main_test
 
 import (
 	"fmt"
-	"math/rand"
 	"path/filepath"
 	"testing"
 
@@ -155,7 +154,7 @@ func testSurgeryClearPageElement(t *testing.T, startIdx, endIdx int, setEndIdxAs
 
 	// clear elements [startIdx, endIdx) in the page
 	rootCmd := main.NewRootCommand()
-	output := filepath.Join(t.TempDir(), fmt.Sprintf("db_%d", rand.Intn(100)))
+	output := filepath.Join(t.TempDir(), "db")
 	rootCmd.SetArgs([]string{
 		"surgery", "clear-page-elements", srcPath,
 		"--output", output,

cmd/bbolt/main.go

@@ -61,14 +61,14 @@ func main() {
 	if err := m.Run(os.Args[1:]...); err == ErrUsage {
 		os.Exit(2)
 	} else if err == ErrUnknownCommand {
-		execute()
+		cobraExecute()
 	} else if err != nil {
 		fmt.Println(err.Error())
 		os.Exit(1)
 	}
 }
 
-func execute() {
+func cobraExecute() {
 	rootCmd := NewRootCommand()
 	if err := rootCmd.Execute(); err != nil {
 		if rootCmd.SilenceErrors {

internal/surgeon/surgeon.go

@@ -20,6 +20,12 @@ func ClearPage(path string, pgId common.Pgid) error {
 	return ClearPageElements(path, pgId, 0, -1)
 }
 
+// ClearPageElements supports clearing elements in both branch and leaf
+// pages. Note the freelist may be cleaned in the meta pages in the following
+// two cases, and bbolt needs to scan the db to reconstruct free list. It may
+// cause some delay on next startup, depending on the db size.
+//  1. Any branch elements are cleared;
+//  2. An object saved in overflow pages is cleared;
 func ClearPageElements(path string, pgId common.Pgid, start, end int) error {
 	// Read the page
 	p, buf, err := guts_cli.ReadPage(path, uint64(pgId))
@@ -93,16 +99,16 @@ func ClearPageElements(path string, pgId common.Pgid, start, end int) error {
 }
 
 func clearFreelist(path string) error {
-	if err := clearFreelistAt(path, 0); err != nil {
+	if err := clearFreelistInMetaPage(path, 0); err != nil {
 		return fmt.Errorf("clearFreelist on meta page 0 failed: %w", err)
 	}
-	if err := clearFreelistAt(path, 1); err != nil {
+	if err := clearFreelistInMetaPage(path, 1); err != nil {
 		return fmt.Errorf("clearFreelist on meta page 1 failed: %w", err)
 	}
 	return nil
 }
 
-func clearFreelistAt(path string, pageId uint64) error {
+func clearFreelistInMetaPage(path string, pageId uint64) error {
 	_, buf, err := guts_cli.ReadPage(path, pageId)
 	if err != nil {
 		return fmt.Errorf("ReadPage %d failed: %w", pageId, err)