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https://issues.apache.org/jira/browse/HIVE-26472?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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John Sherman reassigned HIVE-26472:
-----------------------------------
Assignee: John Sherman
> Concurrent UPDATEs can cause duplicate rows
> -------------------------------------------
>
> Key: HIVE-26472
> URL: https://issues.apache.org/jira/browse/HIVE-26472
> Project: Hive
> Issue Type: Bug
> Components: HiveServer2
> Affects Versions: 4.0.0-alpha-1
> Reporter: John Sherman
> Assignee: John Sherman
> Priority: Critical
> Labels: pull-request-available
> Attachments: debug.diff
>
> Time Spent: 20m
> Remaining Estimate: 0h
>
> Concurrent UPDATEs to the same table can cause duplicate rows when the
> following occurs:
> Two UPDATEs get assigned txnIds and writeIds like this:
> UPDATE #1 = txnId: 100 writeId: 50 <--- commits first
> UPDATE #2 = txnId: 101 writeId: 49
> To replicate the issue:
> I applied the attach debug.diff patch which adds hive.lock.sleep.writeid
> (which controls the amount to sleep before acquiring a writeId) and
> hive.lock.sleep.post.writeid (which controls the amount to sleep after
> acquiring a writeId).
> {code:java}
> CREATE TABLE test_update(i int) STORED AS ORC
> TBLPROPERTIES('transactional'="true");
> INSERT INTO test_update VALUES (1);
> Start two beeline connections.
> In connection #1 - run:
> set hive.driver.parallel.compilation = true;
> set hive.lock.sleep.writeid=5s;
> update test_update set i = 1 where i = 1;
> Wait one second and in connection #2 - run:
> set hive.driver.parallel.compilation = true;
> set hive.lock.sleep.post.writeid=10s;
> update test_update set i = 1 where i = 1;
> After both updates complete - it is likely that test_update contains two rows
> now.
> {code}
> HIVE-24211 seems to address the case when:
> UPDATE #1 = txnId: 100 writeId: 50
> UPDATE #2 = txnId: 101 writeId: 49 <--- commits first (I think this causes
> UPDATE #1 to detect the snapshot is out of date because commitedTxn > UPDATE
> #1s txnId)
> A possible work around is to set hive.driver.parallel.compilation = false,
> but this would only help in cases there is only one HS2 instance.
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