[BUG]: return odd keys bytes when scaning with prefix

[francisoliverlee]

What version of Badger are you using?

version: github.com/dgraph-io/badger/v4 v4.2.0

What version of Go are you using?

1.20

Have you tried reproducing the issue with the latest release?

No

What is the hardware spec (RAM, CPU, OS)?

macos m1 2022

What steps will reproduce the bug?

• describe
  i find an odd thing and solve it, but not sure what happened, can anyone help ?
  when doing for loop, value in tmpKeys are correct, but when exec "return keys, err", values-in-return-keys are not the same with values-in-tmpKeys-in-for-loop.
  and values-in-return-keys are not exist in db.
  for example
  keyPrefix := "cluster#broker#name#@cluster-test-1@", and returns are as follows that not exist in db

  cluster#broker#name#@cluster-test@broker-test-890
  cluster#broker#name#@cluster-test@broker-test-9-1
  cluster#broker#name#@cluster-test@broker-test-9010
  cluster#broker#name#@cluster-test@broker-test-9111
  cluster#broker#name#@cluster-test@broker-test-922
  cluster#broker#name#@cluster-test@broker-test-933
  

• wrong source code

  func (b badgerStore) KeysWithoutValues(bucket string, pattern []byte) (keys [][]byte, err error) {
  	b.logKey("KeysWithoutValues", pattern)
  	err = b.db.View(func(txn *badger.Txn) error {
  		it := txn.NewIterator(badger.IteratorOptions{
  			PrefetchValues: false,
  			PrefetchSize:   100,
  			Reverse:        false,
  			AllVersions:    false,
  		})
  		defer it.Close()
  		prefix := pattern
  
  		var tmpKeys [][]byte
  		for it.Seek(prefix); it.ValidForPrefix(prefix); it.Next() {
  			item := it.Item()
  			if item.IsDeletedOrExpired() {
  				continue
  			}
  			k := item.Key()
  			tmpKeys = append(tmpKeys, k)
  		}
  		keys = tmpKeys
  		return nil
  	})
  
  	return keys, err
  }

Expected behavior and actual result.

return right keys with prefix scaning

Additional information

• solve it myself
  when return keys []byte, i change it to string as following codes, then get it right.

func (b badgerStore) KeyStringsWithoutValues(bucket string, pattern []byte) (keys []string, err error) {
	b.logKey("KeyStringsWithoutValues", pattern)
	err = b.db.View(func(txn *badger.Txn) error {
		it := txn.NewIterator(badger.IteratorOptions{
			PrefetchValues: false,
			PrefetchSize:   100,
			Reverse:        false,
			AllVersions:    false,
		})
		defer it.Close()
		for it.Seek(pattern); it.ValidForPrefix(pattern); it.Next() {
			item := it.Item()
			if item.IsDeletedOrExpired() {
				continue
			}
			k := item.Key()
			keys = append(keys, string(k))

		}
		return nil
	})

	return keys, err
}

[iwind]

Please change item.Key() to item.KeyCopy():

...
k := item.KeyCopy(nil)
keys = append(keys, k)
...