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Date: Tue, 4 Apr 2017 03:47:41 +0000 (UTC)
From: "Eugene Koifman (JIRA)" <jira@apache.org>
To: issues@hive.apache.org
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Subject: [jira] [Updated] (HIVE-12636) Ensure that all queries (with
 DbTxnManager) run in a transaction
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archived-at: Tue, 04 Apr 2017 03:47:45 -0000


     [ https://issues.apache.org/jira/browse/HIVE-12636?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Eugene Koifman updated HIVE-12636:
----------------------------------
    Attachment: HIVE-12636.03.patch

> Ensure that all queries (with DbTxnManager) run in a transaction
> ----------------------------------------------------------------
>
>                 Key: HIVE-12636
>                 URL: https://issues.apache.org/jira/browse/HIVE-12636
>             Project: Hive
>          Issue Type: Improvement
>          Components: Transactions
>    Affects Versions: 1.0.0
>            Reporter: Eugene Koifman
>            Assignee: Eugene Koifman
>            Priority: Critical
>         Attachments: HIVE-12636.01.patch, HIVE-12636.02.patch, HIVE-12636.03.patch
>
>
> Assuming Hive is using DbTxnManager
> Currently (as of this writing only auto commit mode is supported), only queries that write to an Acid table start a transaction.
> Read-only queries don't open a txn but still acquire locks.
> This makes internal structures confusing/odd.
> The are constantly 2 code paths to deal with which is inconvenient and error prone.
> Also, a txn id is convenient "handle" for all locks/resources within a txn.
> Doing thing would mean the client no longer needs to track locks that it acquired.  This enables further improvements to metastore side of Acid.
> # add metastore call to openTxn() and acquireLocks() in a single call.  this it to make sure perf doesn't degrade for read-only query.  (Would also be useful for auto commit write queries)
> # Should RO queries generate txn ids from the same sequence?  (they could for example use negative values of a different sequence).  Txnid is part of the delta/base file name.  Currently it's 7 digits.  If we use the same sequence, we'll exceed 7 digits faster. (possible upgrade issue).  On the other hand there is value in being able to pick txn id and commit timestamp out of the same logical sequence.


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