Github user marmbrus commented on a diff in the pull request:
https://github.com/apache/spark/pull/6782#discussion_r32867754
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/datetimeFunctions.scala
---
@@ -0,0 +1,176 @@
+/*
+ * 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.spark.sql.catalyst.expressions
+
+import org.apache.spark.sql.catalyst.analysis.TypeCheckResult
+import
org.apache.spark.sql.catalyst.expressions.codegen.{GeneratedExpressionCode,
CodeGenContext}
+import org.apache.spark.sql.catalyst.util.DateUtils
+import org.apache.spark.sql.types._
+import org.apache.spark.unsafe.types.UTF8String
+
+/**
+ * Adds a number of days to startdate: date_add('2008-12-31', 1) =
'2009-01-01'.
+ */
+case class DateAdd(startDate: Expression, days: Expression) extends
Expression {
+ override def children: Seq[Expression] = startDate :: days :: Nil
+
+ override def foldable: Boolean = startDate.foldable && days.foldable
+ override def nullable: Boolean = startDate.nullable || days.nullable
+
+ override def checkInputDataTypes(): TypeCheckResult = {
+ val supportedLeftType = Seq(StringType, DateType, TimestampType,
NullType)
+ if (!supportedLeftType.contains(startDate.dataType)) {
+ TypeCheckResult.TypeCheckFailure(
+ s"type of startdate expression in DateAdd should be
string/timestamp/date," +
+ s" not ${startDate.dataType}")
+ } else if (days.dataType != IntegerType && days.dataType != NullType) {
+ TypeCheckResult.TypeCheckFailure(
+ s"type of days expression in DateAdd should be int, not
${days.dataType}.")
+ } else {
+ TypeCheckResult.TypeCheckSuccess
+ }
+ }
+
+ override def dataType: DataType = StringType
--- End diff --
In general though we cast back to a string whenever you need to. From an
efficiency stand point it seems much better to keep it a date.
/cc @rxin
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