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From "Eugene Koifman (JIRA)" <>
Subject [jira] [Updated] (HIVE-12636) Ensure that all queries (with DbTxnManager) run in a transaction
Date Mon, 01 May 2017 16:45:05 GMT


Eugene Koifman updated HIVE-12636:
    Fix Version/s: 3.0.0

> Ensure that all queries (with DbTxnManager) run in a transaction
> ----------------------------------------------------------------
>                 Key: HIVE-12636
>                 URL:
>             Project: Hive
>          Issue Type: Improvement
>          Components: Transactions
>    Affects Versions: 1.0.0
>            Reporter: Eugene Koifman
>            Assignee: Eugene Koifman
>            Priority: Critical
>             Fix For: 3.0.0
>         Attachments: HIVE-12636.01.patch, HIVE-12636.02.patch, HIVE-12636.03.patch, HIVE-12636.04.patch,
HIVE-12636.05.patch, HIVE-12636.06.patch, HIVE-12636.07.patch, HIVE-12636.09.patch, HIVE-12636.10.patch,
HIVE-12636.12.patch, HIVE-12636.13.patch, HIVE-12636.17.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
> # 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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