Fix when inserting json, nil in json causes error

lib/column/json.go

@@ -427,6 +427,12 @@ func iterateMap(mapVal reflect.Value, col JSONParent, preFill int) error {
 	addedColumns := make([]string, len(mapVal.MapKeys()), len(mapVal.MapKeys()))
 	newColumn := false
 	for i, key := range mapVal.MapKeys() {
+		if newColumn {
+			// reset as otherwise prefill overflow to other fields. But don't reset if this prefill has come from
+			// a higher level
+			preFill = 0
+		}
+
 		name := getMapFieldName(key.Interface().(string))
 		if _, ok := columnLookup[name]; !ok && len(currentColumns) > 0 {
 			// new column - need to handle
@@ -471,11 +477,6 @@ func iterateMap(mapVal reflect.Value, col JSONParent, preFill int) error {
 			}
 		}
 		addedColumns[i] = name
-		if newColumn {
-			// reset as otherwise prefill overflow to other fields. But don't reset if this prefill has come from
-			// a higher level
-			preFill = 0
-		}
 	}
 	// handle missing
 	missingColumns := difference(currentColumns, addedColumns)

lib/column/json_test.go

@@ -0,0 +1,65 @@
+// Licensed to ClickHouse, Inc. under one or more contributor
+// license agreements. See the NOTICE file distributed with
+// this work for additional information regarding copyright
+// ownership. ClickHouse, Inc. licenses this file to you 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.
+
+package column
+
+import (
+	"reflect"
+	"testing"
+	"time"
+)
+
+// will got new map to different order
+func getMapRefByMapForTest(myMap map[string]interface{}) reflect.Value {
+	newMap := map[string]interface{}{}
+	for k := range myMap {
+		newMap[k] = myMap[k]
+	}
+
+	return reflect.ValueOf(newMap)
+}
+
+func Test_iterateMap(t *testing.T) {
+	myMap := map[string]interface{}{
+		"col1": int64(1),
+		"col2": time.Date(2022, 11, 21, 16, 21, 0, 0, time.Local),
+		"col3": nil,
+		"col4": "1",
+	}
+
+	col := &JSONObject{
+		columns:  []JSON{},
+		name:     "MyJson",
+		root:     true,
+		encoding: 0,
+	}
+
+	preFill := 0
+	for i := 0; i < 1000; i++ {
+		newMap := getMapRefByMapForTest(myMap)
+		err := iterateMap(newMap, col, preFill)
+		if err != nil {
+			t.Errorf("iterateMap got err: %v", err)
+		}
+	}
+
+	for _, v := range col.columns {
+		if v.Rows() != 1000 {
+			t.Errorf("iterateMap unstable!")
+		}
+	}
+}