dongjoon-hyun commented on a change in pull request #31030:
URL: https://github.com/apache/spark/pull/31030#discussion_r552318233



##########
File path: sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveUtils.scala
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@@ -130,7 +130,10 @@ private[spark] object HiveUtils extends Logging {
 
   val CONVERT_METASTORE_ORC = buildConf("spark.sql.hive.convertMetastoreOrc")
     .doc("When set to true, the built-in ORC reader and writer are used to 
process " +
-      "ORC tables created by using the HiveQL syntax, instead of Hive serde.")
+      "ORC tables created by using the HiveQL syntax, instead of Hive serde." +
+      "Enabling this parameter will cause insert overwrite when reading the 
table," +
+      "and the file format of this table is ORC This error will be thrown[], " 
+

Review comment:
       @dh20 . It seems that you want to describe one of the differences 
between Spark data source tables and Hive serde tables. May I ask a few 
questions?
   
   - Is the situation different from `Parquet`? Parquet also has the same conf 
`spark.sql.hive.convertMetastoreParquet`.
   
   - Is the added statement correct always? Specifically, the following 
statement looks wrong in some situations. For example, did you try to use 
`PartitionOverwriteMode.DYNAMIC`?
   > When I query an orc format hive table and overwrite the query result into 
this orc table, sparksql will throw this error -> 
[org.apache.spark.sql.AnalysisException: Cannot overwrite a path that is also 
being read from], when I set this parameter to false, Hql will execute normally
   
   - Which Apache Spark version are you using? The situation will be changed 
according to the Spark versions. For example,
     - SPARK-30112 implemented `Allow insert overwrite same table if using 
dynamic partition overwrite` at Apache Spark 3.0.0. 
     - SPARK-33887 is also trying to implement `Allow insert overwrite same 
table with static partition if using dynamic partition overwrite mode` at 
Apache Spark 3.2.0.




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