Github user marmbrus commented on a diff in the pull request:
https://github.com/apache/spark/pull/15702#discussion_r85845880
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/EventTimeWatermarkExec.scala
---
@@ -0,0 +1,93 @@
+/*
+ * 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.execution.streaming
+
+import org.apache.spark.rdd.RDD
+import org.apache.spark.sql.catalyst.InternalRow
+import org.apache.spark.sql.catalyst.expressions.{Attribute,
UnsafeProjection}
+import org.apache.spark.sql.catalyst.plans.logical.EventTimeWatermark
+import org.apache.spark.sql.execution.SparkPlan
+import org.apache.spark.sql.types.MetadataBuilder
+import org.apache.spark.unsafe.types.CalendarInterval
+import org.apache.spark.util.AccumulatorV2
+
+class MaxLong(protected var currentValue: Long = 0)
+ extends AccumulatorV2[Long, Long]
+ with Serializable {
+
+ override def isZero: Boolean = value == 0
+ override def value: Long = currentValue
+ override def copy(): AccumulatorV2[Long, Long] = new
MaxLong(currentValue)
+
+ override def reset(): Unit = {
+ currentValue = 0
+ }
+
+ override def add(v: Long): Unit = {
+ if (value < v) { currentValue = v }
+ }
+
+ override def merge(other: AccumulatorV2[Long, Long]): Unit = {
+ if (currentValue < other.value) {
+ currentValue = other.value
+ }
+ }
+}
+
+/**
+ * Used to mark a column as the containing the event time for a given
record. In addition to
+ * adding appropriate metadata to this column, this operator also tracks
the maximum observed event
+ * time. Based on the maximum observed time and a user specified delay, we
can calculate the
+ * `watermark` after which we assume we will no longer see late records
for a particular time
+ * period.
+ */
+case class EventTimeWatermarkExec(
+ eventTime: Attribute,
+ delay: CalendarInterval,
+ child: SparkPlan) extends SparkPlan {
+
+ // TODO: Use Spark SQL Metrics?
+ val maxEventTime = new MaxLong
--- End diff --
@zsxwing am I doing this right?
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