GitHub user gatorsmile opened a pull request:
https://github.com/apache/spark/pull/15926
[SPARK-16803] [SQL] SaveAsTable does not work when target table is a Hive
serde table
### What changes were proposed in this pull request?
In Spark 2.0, `SaveAsTable` does not work when the target table is a Hive
serde table, but Spark 1.6 works.
**Spark 1.6**
``` Scala
scala> sql("create table sample.sample stored as SEQUENCEFILE as select 1
as key, 'abc' as value")
res2: org.apache.spark.sql.DataFrame = []
scala> val df = sql("select key, value as value from sample.sample")
df: org.apache.spark.sql.DataFrame = [key: int, value: string]
scala> df.write.mode("append").saveAsTable("sample.sample")
scala> sql("select * from sample.sample").show()
+---+-----+
|key|value|
+---+-----+
| 1| abc|
| 1| abc|
+---+-----+
```
**Spark 2.0**
``` Scala
scala> df.write.mode("append").saveAsTable("sample.sample")
org.apache.spark.sql.AnalysisException: Saving data in MetastoreRelation
sample, sample
is not supported.;
```
So far, we do not plan to support it in Spark 2.1 due to the risk. Spark
1.6 works because it internally uses insertInto. But, if we change it back it
will break the semantic of saveAsTable (this method uses by-name resolution
instead of using by-position resolution used by insertInto). More extra changes
are needed to support `hive` as a `format` in DataFrameWriter.
Instead, users should use insertInto API. This PR corrects the error
messages. Users can understand how to bypass it before we support it in a
separate PR.
### How was this patch tested?
Test cases are added
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/gatorsmile/spark saveAsTableFix5
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/15926.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #15926
----
commit 887b4275d26bb04783abee6c72607b62c41034bf
Author: gatorsmile <[email protected]>
Date: 2016-11-18T02:16:13Z
fix
commit 061c0d34aa7b5b64b7fa490e969d11c7733bc26f
Author: gatorsmile <[email protected]>
Date: 2016-11-18T02:29:33Z
improve the error message
----
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