Github user ericl commented on a diff in the pull request:
https://github.com/apache/spark/pull/13456#discussion_r65602557
--- Diff:
sql/core/src/test/scala/org/apache/spark/sql/execution/benchmark/WideSchemaBenchmark.scala
---
@@ -0,0 +1,285 @@
+/*
+ * 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
+
+import org.apache.spark.SparkFunSuite
+import org.apache.spark.sql.functions._
+import org.apache.spark.util.Benchmark
+
+/**
+ * Benchmark for performance with very wide and nested DataFrames.
+ * To run this:
+ * build/sbt "sql/test-only *WideSchemaBenchmark"
+ */
+class WideSchemaBenchmark extends SparkFunSuite {
+ private val scaleFactor = 100000
+ private val widthsToTest = Seq(1, 10, 100, 1000, 2500)
+ private val depthsToTest = Seq(1, 10, 100, 250)
+ assert(scaleFactor > widthsToTest.max)
+
+ private lazy val sparkSession = SparkSession.builder
+ .master("local[1]")
+ .appName("microbenchmark")
+ .getOrCreate()
+
+ import sparkSession.implicits._
+
+ ignore("parsing large select expressions") {
+ val benchmark = new Benchmark("parsing large select", 1)
+ for (width <- widthsToTest) {
+ val selectExpr = (1 to width).map(i => s"id as a_$i")
+ benchmark.addCase(s"$width select expressions") { iter =>
+ sparkSession.range(1).toDF.selectExpr(selectExpr: _*)
+ }
+ }
+ benchmark.run()
+
+ /*
+ OpenJDK 64-Bit Server VM 1.8.0_66-internal-b17 on Linux
4.2.0-36-generic
--- End diff --
I addressed this in https://github.com/apache/spark/pull/13472: in practice
the times didn't seem to change by that much (maybe 1.5x faster for the smaller
cases).
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