Need to document the sorting order of the keys

[h12w]

There is no document describing how keys are sorted, so I have to test it with the code below.

It seems the ordering should be described as something like "byte-wise prefix order", similar to big endian but the keys are aligned from the least significant byte, and "no byte" is smaller than "byte zero" (the shorter the smaller).

I think the behavior should be clarified in the document so that we can depend on the sorting more confidently.

The test code:

func TestKeyOrder(t *testing.T) {
	dir := "test_order"
	if err := os.MkdirAll(dir, 0755); err != nil {
		t.Fatal(err)
	}
	defer os.RemoveAll(dir)
	db, err := openBadger(dir)
	if err != nil {
		t.Fatal(err)
	}
	defer db.Close()
	if err := db.Update(func(txn *badger.Txn) error {
		if err := txn.Set([]byte{0, 0}, nil); err != nil {
			return err
		}
		if err := txn.Set([]byte{0, 1}, nil); err != nil {
			return err
		}
		if err := txn.Set([]byte{0, 2}, nil); err != nil {
			return err
		}
		if err := txn.Set([]byte{1, 0}, nil); err != nil {
			return err
		}
		if err := txn.Set([]byte{1, 1}, nil); err != nil {
			return err
		}
		if err := txn.Set([]byte{1, 2}, nil); err != nil {
			return err
		}
		if err := txn.Set([]byte{1, 2, 0}, nil); err != nil {
			return err
		}
		if err := txn.Set([]byte{2, 0}, nil); err != nil {
			return err
		}
		if err := txn.Set([]byte{2, 1}, nil); err != nil {
			return err
		}
		if err := txn.Set([]byte{2, 2}, nil); err != nil {
			return err
		}
		return nil
	}); err != nil {
		t.Fatal(err)
	}
	if err := db.View(func(txn *badger.Txn) error {
		opt := badger.DefaultIteratorOptions
		// opt.Reverse = true
		it := txn.NewIterator(opt)
		for it.Rewind(); it.Valid(); it.Next() {
			item := it.Item()
			k := item.Key()
			fmt.Println(k)
		}
		return nil
	}); err != nil {
		t.Fatal(err)
	}
}

[manishrjain]

It's byte-wise lexicographical sorting. We can probably clarify that in the README.

https://golang.org/pkg/bytes/#Compare

[h12w]

Yes, "lexicographic" is exactly the word I'm trying to say. Thanks!