Github user zsxwing commented on a diff in the pull request:
https://github.com/apache/spark/pull/12008#discussion_r57840756
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/TimeWindow.scala
---
@@ -0,0 +1,137 @@
+/*
+ * 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.commons.lang.StringUtils
+
+import org.apache.spark.sql.AnalysisException
+import org.apache.spark.sql.catalyst.analysis.TypeCheckResult
+import
org.apache.spark.sql.catalyst.analysis.TypeCheckResult.TypeCheckFailure
+import org.apache.spark.sql.types._
+import org.apache.spark.unsafe.types.CalendarInterval
+
+case class TimeWindow(
+ timeColumn: Expression,
+ windowDuration: Long,
+ slideDuration: Long,
+ startTime: Long,
+ private var outputColumnName: String = "window") extends
UnaryExpression
+ with ImplicitCastInputTypes
+ with Unevaluable
+ with NonSQLExpression {
+
+ override def child: Expression = timeColumn
+ override def inputTypes: Seq[AbstractDataType] = Seq(TimestampType)
+ override def dataType: DataType = new StructType()
+ .add(StructField("start", TimestampType))
+ .add(StructField("end", TimestampType))
+
+ // This expression is replaced in the analyzer.
+ override lazy val resolved = false
+
+ override def checkInputDataTypes(): TypeCheckResult = {
+ val dataTypeCheck = super.checkInputDataTypes()
+ if (dataTypeCheck.isSuccess) {
+ if (windowDuration <= 0) {
+ return TypeCheckFailure(s"The window duration ($windowDuration)
must be greater than 0.")
+ }
+ if (slideDuration <= 0) {
+ return TypeCheckFailure(s"The slide duration ($slideDuration) must
be greater than 0.")
+ }
+ if (startTime < 0) {
+ return TypeCheckFailure(s"The start time ($startTime) must be
greater than or equal to 0.")
+ }
+ if (slideDuration > windowDuration) {
+ return TypeCheckFailure(s"The slide duration ($slideDuration) must
be less than or equal to the " +
+ s"windowDuration ($windowDuration).")
+ }
+ if (startTime >= slideDuration) {
+ return TypeCheckFailure(s"The start time ($startTime) must be less
than the " +
+ s"slideDuration ($slideDuration).")
+ }
+ return dataTypeCheck
+ } else {
+ return dataTypeCheck
+ }
+ }
+ /**
+ * Validate the inputs for the window duration, slide duration, and
start time.
+ *
+ * @return Some string with a useful error message for the invalid input.
+ */
+ def validate(): Option[String] = {
+ if (windowDuration <= 0) {
+ return Some(s"The window duration ($windowDuration) must be greater
than 0.")
+ }
+ if (slideDuration <= 0) {
+ return Some(s"The slide duration ($slideDuration) must be greater
than 0.")
+ }
+ if (startTime < 0) {
+ return Some(s"The start time ($startTime) must be greater than or
equal to 0.")
+ }
+ if (slideDuration > windowDuration) {
+ return Some(s"The slide duration ($slideDuration) must be less than
or equal to the " +
+ s"windowDuration ($windowDuration).")
+ }
+ if (startTime >= slideDuration) {
+ return Some(s"The start time ($startTime) must be less than the " +
+ s"slideDuration ($slideDuration).")
+ }
+ None
+ }
+}
+
+object TimeWindow {
+ /**
+ * Parses the interval string for a valid time duration.
CalendarInterval expects interval
+ * strings to start with the string `interval`. For usability, we
prepend `interval` to the string
+ * if the user ommitted it.
+ *
+ * @param interval The interval string
+ * @return The interval duration in seconds. SparkSQL casts
TimestampType to Long in seconds,
+ * therefore we use seconds here as well.
+ */
+ private def getIntervalInSeconds(interval: String): Long = {
+ if (StringUtils.isBlank(interval)) {
+ throw new IllegalArgumentException(
+ "The window duration, slide duration and start time cannot be null
or blank.")
+ }
+ val intervalString = if (interval.startsWith("interval")) {
+ interval
+ } else {
+ "interval " + interval
+ }
+ val cal = CalendarInterval.fromString(intervalString)
+ if (cal == null) {
+ throw new IllegalArgumentException(
+ s"The provided interval ($interval) did not correspond to a valid
interval string.")
+ }
+ (cal.months * 4 * CalendarInterval.MICROS_PER_WEEK + cal.microseconds)
/ 1000000
--- End diff --
`4 weeks == 1 month` looks weird. Maybe define `window("timestamp", "1
month")` as `groupBy(getMonthInYear("timestamp"))` is more intuitive?
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