adde (#28)

Author: AskAlexSharov

mdbx/txn.go

@@ -684,3 +684,22 @@ func (txn *Txn) Sequence(dbi DBI, increment uint64) (uint64, error) {
 	}
 	return uint64(res), nil
 }
+
+// ListDBI - return all dbi names. they stored as keys of un-named (main) dbi
+func (txn *Txn) ListDBI() (res []string, err error) {
+	root, err := txn.OpenRoot(0)
+	if err != nil {
+		return nil, err
+	}
+	c, err := txn.OpenCursor(root)
+	if err != nil {
+		return nil, err
+	}
+	for k, _, err := c.Get(nil, nil, First); k != nil; k, _, err = c.Get(nil, nil, Next) {
+		if err != nil {
+			return nil, err
+		}
+		res = append(res, string(k))
+	}
+	return res, nil
+}

mdbx/txn_test.go

@@ -982,6 +982,53 @@ func TestSequence(t *testing.T) {
 	}
 }
 
+func TestListDBI(t *testing.T) {
+	env := setup(t)
+
+	if err := env.View(func(txn *Txn) (err error) {
+		v, err := txn.ListDBI()
+		if err != nil {
+			return err
+		}
+		if len(v) != 0 {
+			t.Errorf("unexpected value: %d (expected %d)", len(v), 0)
+		}
+
+		return nil
+	}); err != nil {
+		t.Errorf("%s", err)
+	}
+
+	if err := env.Update(func(txn *Txn) (err error) {
+		_, err = txn.OpenDBISimple("testdb", Create)
+		if err != nil {
+			return err
+		}
+		_, err = txn.OpenDBISimple("testdb2", Create)
+		return err
+	}); err != nil {
+		t.Errorf("%s", err)
+		return
+	}
+
+	if err := env.View(func(txn *Txn) (err error) {
+		v, err := txn.ListDBI()
+		if err != nil {
+			return err
+		}
+		if v == nil {
+			t.Errorf("unexpected nil")
+		}
+		if len(v) != 2 {
+			t.Errorf("unexpected value: %d (expected %d)", len(v), 2)
+		}
+
+		return nil
+	}); err != nil {
+		t.Errorf("%s", err)
+	}
+}
+
 func BenchmarkTxn_abort(b *testing.B) {
 	env := setup(b)