GitHub user liancheng opened a pull request:
https://github.com/apache/spark/pull/9911
[WIP][SPARK-9686][SQL] Redirect JDBC metadata calls to Spark SQL metadata
Hive client
This PR is based on the patch @navis provided in [SPARK-9686][1].
Basically, it overrides all JDBC metadata related methods in
`SparkSQLCLIService`, overrides session `HiveConf` with proper configurations,
and wraps the original calls with `hiveContext.metadataHive.withHiveState`, so
that metadata stored in the real Hive metastore can be retrieved.
Unfortunately, both @navis and I observed that this approach doesn't play
well with embedded metastore, because Hive somehow tries to establish multiple
connections to the local Derby metastore database while Derby doesn't support
multi-connection.
I've being digging this for a while, but failed to figure out a valid
fix/workaround for this issue. (So the test case added in this PR doesn't
pass.) My impression is that, somehow the `HiveMetaStoreClient` belongs to
metadata Hive client got a snapshot of the `HiveConf` of the execution Hive
client, thus makes Hive try to establish a new connection instead of reusing
the existing connection because this `HiveConf` is considered to be
"[incompatible][2]" with the session `HiveConf`.
[1]: https://issues.apache.org/jira/browse/SPARK-9686
[2]:
https://github.com/apache/hive/blob/release-1.2.1/metastore/src/java/org/apache/hadoop/hive/metastore/HiveMetaStoreClient.java#L279-L297
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/liancheng/spark spark-9686.jdbc-metadata
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/9911.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 #9911
----
commit 65aa390e5fc60fc7da7dcc83a7ef0033c7795db7
Author: Cheng Lian <l...@databricks.com>
Date: 2015-11-21T09:10:12Z
WIP
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