Planbuilder: Add fuzzer

Signed-off-by: AdamKorcz <adam@adalogics.com>

go/vt/vtgate/planbuilder/fuzz.go

@@ -0,0 +1,51 @@
+/*
+Copyright 2021 The Vitess Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+// +build gofuzz
+
+package planbuilder
+
+import (
+	"vitess.io/vitess/go/vt/key"
+	topodatapb "vitess.io/vitess/go/vt/proto/topodata"
+	"vitess.io/vitess/go/vt/sqlparser"
+	"vitess.io/vitess/go/vt/vtgate/semantics"
+	"vitess.io/vitess/go/vt/vtgate/vindexes"
+)
+
+var _ semantics.SchemaInformation = (*fakeFuzzSI)(nil)
+
+type fakeFuzzSI struct {
+	tables map[string]*vindexes.Table
+}
+
+// Helper func:
+func (s *fakeFuzzSI) FindTableOrVindex(tablename sqlparser.TableName) (*vindexes.Table, vindexes.Vindex, string, topodatapb.TabletType, key.Destination, error) {
+	return s.tables[sqlparser.String(tablename)], nil, "", 0, nil, nil
+}
+
+// FuzzAnalyse implements the fuzzer
+func FuzzAnalyse(data []byte) int {
+	tree, err := sqlparser.Parse(string(data))
+	if err != nil {
+		return -1
+	}
+	semTable, err := semantics.Analyse(tree, &fakeFuzzSI{})
+	if err != nil {
+		return 0
+	}
+	_, _ = createQGFromSelect(tree.(*sqlparser.Select), semTable)
+	return 1
+}