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https://issues.apache.org/jira/browse/SPARK-7276?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14522153#comment-14522153
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Reynold Xin commented on SPARK-7276:
------------------------------------
The problem is having too many projects (each new column adds a project). You
can speed this up significantly right now by using a single .select to add all
the columns.
For a fix quick, I think we can have dataframe.select collapses Projects, i.e.
if the last logical operator is a Project, simply merge the two Projects.
However, this will break caching semantics, but we can make caching detection
smarter in the future.
[~cloud_fan] would you like to give it a shot to collapse projects in
dataframe.select?
> withColumn is very slow on dataframe with large number of columns
> -----------------------------------------------------------------
>
> Key: SPARK-7276
> URL: https://issues.apache.org/jira/browse/SPARK-7276
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 1.3.1
> Reporter: Alexandre CLEMENT
>
> The code snippet demonstrates the problem.
> {code}
> import org.apache.spark.sql._
> import org.apache.spark.sql.types._
> val sparkConf = new SparkConf().setAppName("Spark
> Test").setMaster(System.getProperty("spark.master", "local[4]"))
> val sc = new SparkContext(sparkConf)
> val sqlContext = new SQLContext(sc)
> import sqlContext.implicits._
> val custs = Seq(
> Row(1, "Bob", 21, 80.5),
> Row(2, "Bobby", 21, 80.5),
> Row(3, "Jean", 21, 80.5),
> Row(4, "Fatime", 21, 80.5)
> )
> var fields = List(
> StructField("id", IntegerType, true),
> StructField("a", IntegerType, true),
> StructField("b", StringType, true),
> StructField("target", DoubleType, false))
> val schema = StructType(fields)
> var rdd = sc.parallelize(custs)
> var df = sqlContext.createDataFrame(rdd, schema)
> for (i <- 1 to 200) {
> val now = System.currentTimeMillis
> df = df.withColumn("a_new_col_" + i, df("a") + i)
> println(s"$i -> " + (System.currentTimeMillis - now))
> }
> df.show()
> {code}
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