[SPARK-17393] [SQL] Error Handling when CTAS Against the Same Data Source Table Using Overwrite Mode

[gatorsmile]

What changes were proposed in this pull request?

When we trying to read a table and then write to the same table using the Overwrite save mode, we got a very confusing error message:
For example,

      Seq((1, 2)).toDF("i", "j").write.saveAsTable("tab1")
      table("tab1").write.mode(SaveMode.Overwrite).saveAsTable("tab1")

Job aborted.
org.apache.spark.SparkException: Job aborted.
    at org.apache.spark.sql.execution.datasources.InsertIntoHadoopFsRelationCommand$$anonfun$run$1.apply$mcV$sp
...
Caused by: org.apache.spark.SparkException: Task failed while writing rows
    at org.apache.spark.sql.execution.datasources.DefaultWriterContainer.writeRows(WriterContainer.scala:266)
    at org.apache.spark.sql.execution.datasources.InsertIntoHadoopFsRelationCommand$$anonfun$run$1$$anonfun$apply$mcV$sp$1.apply(InsertIntoHadoopFsRelationCommand.scala:143)
    at org.apache.spark.sql.execution.datasources

After the PR, we will issue an AnalysisException:

Cannot overwrite table `tab1` that is also being read from

How was this patch tested?

Added test cases.

[SparkQA]

Test build #64914 has finished for PR 14954 at commit 85e51dc.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[gatorsmile]

cc @cloud-fan @yhuai

[gatorsmile]

Should we issue error messages when the operation is insertInto but the mode is Ignore or ErrorIfExists?

[cloud-fan]

yea I think we should, let's do it in follow-up PR

[gatorsmile]

Sure, will do it. Thanks!

[cloud-fan]

LGTM, merging to master!