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From wuchong <...@git.apache.org>
Subject [GitHub] flink pull request #4138: [FLINK-6925][table]Add CONCAT/CONCAT_WS supported ...
Date Wed, 28 Jun 2017 05:49:39 GMT
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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