[GitHub] gatorsmile commented on a change in pull request #23285: [SPARK-26224][SQL] Warn and advice the user when creating many project on subsequent calls to withColumn

[GitBox <gi...@apache.org>]

gatorsmile commented on a change in pull request #23285: [SPARK-26224][SQL] Warn and advice the user when creating many project on subsequent calls to withColumn
URL: https://github.com/apache/spark/pull/23285#discussion_r247584595
 
 

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 File path: sql/catalyst/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala
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 @@ -1621,6 +1621,17 @@ object SQLConf {
     .intConf
     .createWithDefault(25)
 
+  val MAX_WITHCOLUMN_PROJECTS = buildConf("spark.sql.withColumn.maxProjects")
+    .internal()
+    .doc("Maximum number of projects on top of a plan when using `Dataset.withColumn`. When the " +
+      "threshold is exceeded, warnings are emitted in order to advice a different approach. " +
+      "This usually happens when adding too many columns in loops using withColumns. Indeed, " +
+      "this pattern can lead to serious performance issues and even OOM. Set to 0 in order to " +
+      "disable completely the check.")
+    .intConf
+    .checkValue(_ >= 0, "The max number of projects cannot be negative.")
+    .createWithDefault(50)
 
 Review comment:
   `50`? Before we doing anything, could you first show the perf number?

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