Github user wuchong commented on a diff in the pull request:
https://github.com/apache/flink/pull/4138#discussion_r124456117
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/runtime/functions/ScalarFunctions.scala
---
@@ -0,0 +1,87 @@
+/*
+ * 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 org.apache.flink.table.runtime.functions
+
+import scala.annotation.varargs
+import java.math.{BigDecimal => JBigDecimal}
+import java.lang.{StringBuffer => JStringBuffer}
+
+/**
+ * Built-in scalar runtime functions.
+ */
+class ScalarFunctions {}
+
+object ScalarFunctions {
+
+ def power(a: Double, b: JBigDecimal): Double = {
+ Math.pow(a, b.doubleValue())
+ }
+
+ /**
+ * Returns the string that results from concatenating the arguments.
+ * Returns NULL if any argument is NULL.
+ */
+ @varargs
+ def concat(args: String*): String = {
+ val sb = new JStringBuffer
+ var i = 0
+ while (i < args.length) {
+ if (args(i) == null) {
+ return null
+ }
+ sb.append(args(i))
+ i += 1
+ }
+ sb.toString
+ }
+
+ /**
+ * Returns the string that results from concatenating the arguments and
separator.
+ * Returns NULL If the separator is NULL.
+ *
+ * Note: CONCAT_WS() does not skip empty strings. However, it does skip
any NULL values after
+ * the separator argument.
+ *
+ * @param args The first element of argument is the separator for the
rest of the arguments.
+ */
+ @varargs
+ def concat_ws(args: String*): String = {
+ val separator = args(0)
+ if (null == separator) {
+ return null
+ }
+
+ val sb = new JStringBuffer
--- End diff --
Please use `StringBuilder` instead of `StringBuffer`.
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