Github user rdblue commented on a diff in the pull request:
https://github.com/apache/spark/pull/18419#discussion_r124331858
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/SQLExecution.scala ---
@@ -100,7 +105,9 @@ object SQLExecution {
// all accumulator metrics will be 0. It will confuse people if we
show them in Web UI.
//
// A real case is the `DataFrame.count` method.
- throw new IllegalArgumentException(s"$EXECUTION_ID_KEY is already
set")
+ throw new IllegalArgumentException(s"$EXECUTION_ID_KEY is already
set, please wrap your " +
--- End diff --
The problem is that this is an easy error to hit and it shouldn't affect
end users. It is better to warn that something is wrong than to fail a job that
would otherwise succeed for a bug in Spark. As for the error message, I think
it is fine if we intend to leave it in. I'd just rather not fail user jobs here.
I assume that DataSource developers will have tests, but probably not ones
that know to set spark.testing. Is there a better way to detect test cases?
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