--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/pkg/controllers/common.go	Wed May 08 10:50:14 2019 +0200
@@ -0,0 +1,43 @@
+// This is Free Software under GNU Affero General Public License v >= 3.0
+// without warranty, see README.md and license for details.
+//
+// SPDX-License-Identifier: AGPL-3.0-or-later
+// License-Filename: LICENSES/AGPL-3.0.txt
+//
+// Copyright (C) 2019 by via donau
+//   – Österreichische Wasserstraßen-Gesellschaft mbH
+// Software engineering by Intevation GmbH
+//
+// Author(s):
+//  * Sascha L. Teichmann <sascha.teichmann@intevation.de>
+
+package controllers
+
+import (
+	"fmt"
+	"strings"
+)
+
+type filterBuilder struct {
+	stmt    strings.Builder
+	args    []interface{}
+	hasCond bool
+}
+
+func (fb *filterBuilder) arg(format string, v ...interface{}) {
+	indices := make([]interface{}, len(v))
+	for i := range indices {
+		indices[i] = len(fb.args) + i + 1
+	}
+	fmt.Fprintf(&fb.stmt, format, indices...)
+	fb.args = append(fb.args, v...)
+}
+
+func (fb *filterBuilder) and(format string, v ...interface{}) {
+	if fb.hasCond {
+		fb.stmt.WriteString(" AND ")
+	} else {
+		fb.hasCond = true
+	}
+	fb.arg(format, v...)
+}