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From zsxwing <...@git.apache.org>
Subject [GitHub] spark pull request: [SPARK-14160] Time Windowing functions for Dat...
Date Wed, 30 Mar 2016 06:11:42 GMT
Github user zsxwing commented on a diff in the pull request:

    https://github.com/apache/spark/pull/12008#discussion_r57840817
  
    --- 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?
    
    This looks hard to implement. Maybe we just don't need to support `month` or `year`.


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