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https://issues.apache.org/jira/browse/HIVE-9223?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14482490#comment-14482490
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Raj Bains commented on HIVE-9223:
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Queries within the same session should execute serially. Hue should open a new
session when you use a new tab. Each tab can be considered a script where
queries run sequentially. Otherwise how can I guarantee that a query creating a
temporary table and the one following it that reads the temporary table are
processed in order? Are we depending on UI tabs for that? The previous MR
behavior seems to be a bug.
> HiveServer2 on Tez doesn't support concurrent queries within one session
> ------------------------------------------------------------------------
>
> Key: HIVE-9223
> URL: https://issues.apache.org/jira/browse/HIVE-9223
> Project: Hive
> Issue Type: Bug
> Components: HiveServer2
> Reporter: Pala M Muthaia
>
> When a user submits multiple queries in the same HS2 session (using thrift
> interface) concurrently, the query goes through the same TezSessionState and
> ends up being submitted to the same Tez AM, and the second query fails with
> the error "App master already running a DAG"
> Is this by design? I looked into the code, and the comments as well as the
> code suggest support only for serial execution of queries within the same
> HiveServer2 session (on tez).
> This works for CLI environment but in a server, it is plausible that client
> sends multiple concurrent queries under the same session (e.g: a web app that
> executes queries for user, such as Cloudera Hue). So shouldn't HS2 on Tez
> implementation support concurrent queries?
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