Add:Support MySQL CHAR_LENGTH function.arana-db#501 (arana-db#544)

* Add:Support MySQL CHAR_LENGTH function.arana-db#501

* Add:Support MySQL CHAR_LENGTH function.arana-db#501

pkg/runtime/function/char_length.go

@@ -0,0 +1,57 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF 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 function
+
+import (
+	"context"
+	"fmt"
+	"unicode/utf8"
+)
+
+import (
+	"github.com/pkg/errors"
+)
+
+import (
+	"github.com/arana-db/arana/pkg/proto"
+)
+
+// FuncCharLength is  https://dev.mysql.com/doc/refman/5.6/en/string-functions.html#function_character-length
+const FuncCharLength = "CHAR_LENGTH"
+
+var _ proto.Func = (*charlengthFunc)(nil)
+
+func init() {
+	proto.RegisterFunc(FuncCharLength, charlengthFunc{})
+}
+
+type charlengthFunc struct{}
+
+func (a charlengthFunc) Apply(ctx context.Context, inputs ...proto.Valuer) (proto.Value, error) {
+	val, err := inputs[0].Value(ctx)
+	if err != nil {
+		return nil, errors.WithStack(err)
+	}
+
+	result := utf8.RuneCountInString(fmt.Sprint(val))
+	return int64(result), nil
+}
+
+func (a charlengthFunc) NumInput() int {
+	return 1
+}

pkg/runtime/function/char_length_test.go

@@ -0,0 +1,54 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF 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 function
+
+import (
+	"context"
+	"fmt"
+	"testing"
+)
+
+import (
+	"github.com/stretchr/testify/assert"
+)
+
+import (
+	"github.com/arana-db/arana/pkg/proto"
+)
+
+func TestCharLength(t *testing.T) {
+	fn := proto.MustGetFunc(FuncCharLength)
+	assert.Equal(t, 1, fn.NumInput())
+	type tt struct {
+		inFirst proto.Value
+		want    int64
+	}
+	for _, v := range []tt{
+		{"Hello世界", 7},
+		{"Hello", 5},
+		{"世界", 2},
+		{"你好世界！", 5},
+	} {
+		t.Run(fmt.Sprint(v.inFirst), func(t *testing.T) {
+			out, err := fn.Apply(context.Background(), proto.ToValuer(v.inFirst))
+			assert.NoError(t, err)
+			assert.Equal(t, v.want, out)
+		})
+	}
+
+}