Github user adrian-ionescu commented on a diff in the pull request:
https://github.com/apache/spark/pull/18159#discussion_r120375471
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/command/FileWritingCommand.scala
---
@@ -0,0 +1,108 @@
+/*
+ * 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.command
+
+import org.apache.spark.SparkContext
+import org.apache.spark.sql.{Row, SparkSession}
+import org.apache.spark.sql.catalyst.{CatalystTypeConverters, InternalRow}
+import org.apache.spark.sql.catalyst.plans.logical
+import org.apache.spark.sql.execution.{SparkPlan, SQLExecution}
+import org.apache.spark.sql.execution.datasources.ExecutedWriteSummary
+import org.apache.spark.sql.execution.metric.{SQLMetric, SQLMetrics}
+import org.apache.spark.util.Utils
+
+/**
+ * A logical command specialized for writing data out.
`FileWritingCommand`s are
+ * wrapped in `FileWritingCommandExec` during execution.
+ */
+trait FileWritingCommand extends logical.Command {
+
+ // The caller of `FileWritingCommand` can replace the metrics location
by providing this external
+ // metrics structure.
+ private var _externalMetrics: Option[Map[String, SQLMetric]] = None
+ private[sql] def withExternalMetrics(map: Map[String, SQLMetric]):
this.type = {
+ _externalMetrics = Option(map)
+ this
+ }
+
+ /**
+ * Those metrics will be updated once the command finishes writing data
out. Those metrics will
+ * be taken by `FileWritingCommandExec` as its metrics when showing in
UI.
+ */
+ def metrics(sparkContext: SparkContext): Map[String, SQLMetric] =
_externalMetrics.getOrElse {
+ Map(
+ // General metrics.
+ "avgTime" -> SQLMetrics.createMetric(sparkContext, "average writing
time (ms)"),
+ "numFiles" -> SQLMetrics.createMetric(sparkContext, "number of
written files"),
+ "numOutputBytes" -> SQLMetrics.createMetric(sparkContext, "bytes of
written output"),
+ "numOutputRows" -> SQLMetrics.createMetric(sparkContext, "number of
output rows"),
+ "numParts" -> SQLMetrics.createMetric(sparkContext, "number of
dynamic part")
+ )
+ }
+
+ /**
+ * Callback function that update metrics collected from the writing
operation.
+ */
+ private[sql] def postDriverMetrics(sparkContext: SparkContext, metrics:
Map[String, SQLMetric])
+ (writeSummaries: Seq[ExecutedWriteSummary]): Unit = {
+ var numPartitions = 0
+ var numFiles = 0
+ var totalNumBytes: Long = 0L
+ var totalNumOutput: Long = 0L
+
+ writeSummaries.foreach { summary =>
+ numPartitions += summary.updatedPartitions.size
+ numFiles += summary.numOutputFile
+ totalNumBytes += summary.numOutputBytes
+ totalNumOutput += summary.numOutputRows
+ }
+
+ // The time for writing individual file can be zero if it's less than
1 ms. Zero values can
+ // lower actual time of writing when calculating average, so excluding
them.
+ val writingTime =
+ Utils.average(writeSummaries.flatMap(_.writingTimePerFile.filter(_ >
0))).toLong
+
+ val metricsNames = metrics.keys.toSeq.sorted
+ val metricsValues = Seq(writingTime, numFiles, totalNumBytes,
totalNumOutput, numPartitions)
+ metricsNames.zip(metricsValues).foreach(x => metrics(x._1).add(x._2))
--- End diff --
I meant user as in caller of this function. This function only works when
the input satisfies some requirements and silently fails otherwise. I get it
that it's a private method, but it's very error prone.
Imagine I want to extend this by adding another metric called
`avgNumFilesPerPart`. If I add it to the end of the `metricsValues` Seq, then
all metrics will get messed up (because of the ordering).
At the very least, leave a comment saying that the `metricValues` need to
be sorted alphabetically (and rename `writingTime` to `avgWritingTime`). But
you should rather consider using a `WriteMetrics` class instead of a Map.
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