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From "Eugene Koifman (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-16832) duplicate ROW__ID possible in multi insert into transactional table
Date Tue, 11 Jul 2017 14:37:00 GMT

    [ https://issues.apache.org/jira/browse/HIVE-16832?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16082294#comment-16082294
] 

Eugene Koifman commented on HIVE-16832:
---------------------------------------


I agree that Compressed OTID is now bigger but I'm not sure how useful it's in the first place.
Suppose you populate a partition via 100 inserts and 1M rows.  So you have 100 OTIDs.
Now if you run an update/delete with some WHERE clause it will match rows randomly wrt OTIDs
on average.
So if this delete generates 500 events, it seems likely that you get a lot of distinct OTIDs
among them.  Perhaps simply relying on the "push down" to delete deltas is enough and we are
better off just keeping 3 arrays.


> duplicate ROW__ID possible in multi insert into transactional table
> -------------------------------------------------------------------
>
>                 Key: HIVE-16832
>                 URL: https://issues.apache.org/jira/browse/HIVE-16832
>             Project: Hive
>          Issue Type: Bug
>          Components: Transactions
>    Affects Versions: 2.2.0
>            Reporter: Eugene Koifman
>            Assignee: Eugene Koifman
>            Priority: Critical
>         Attachments: HIVE-16832.01.patch, HIVE-16832.03.patch, HIVE-16832.04.patch, HIVE-16832.05.patch,
HIVE-16832.06.patch, HIVE-16832.08.patch, HIVE-16832.09.patch, HIVE-16832.10.patch, HIVE-16832.11.patch,
HIVE-16832.14.patch, HIVE-16832.15.patch, HIVE-16832.16.patch, HIVE-16832.17.patch, HIVE-16832.18.patch,
HIVE-16832.19.patch, HIVE-16832.20.patch, HIVE-16832.20.patch
>
>
> {noformat}
>  create table AcidTablePart(a int, b int) partitioned by (p string) clustered by (a)
into 2 buckets stored as orc TBLPROPERTIES ('transactional'='true');
>  create temporary table if not exists data1 (x int);
>  insert into data1 values (1);
>  from data1
>    insert into AcidTablePart partition(p) select 0, 0, 'p' || x
>    insert into AcidTablePart partition(p='p1') select 0, 1
> {noformat}
> Each branch of this multi-insert create a row in partition p1/bucket0 with ROW__ID=(1,0,0).
> The same can happen when running SQL Merge (HIVE-10924) statement that has both Insert
and Update clauses when target table has _'transactional'='true','transactional_properties'='default'_
 (see HIVE-14035).  This is so because Merge is internally run as a multi-insert statement.
> The solution relies on statement ID introduced in HIVE-11030.  Each Insert clause of
a multi-insert is gets a unique ID.
> The ROW__ID.bucketId now becomes a bit packed triplet (format version, bucketId, statementId).
> (Since ORC stores field names in the data file we can't rename ROW__ID.bucketId).
> This ensures that there are no collisions and retains desired sort properties of ROW__ID.
> In particular _SortedDynPartitionOptimizer_ works w/o any changes even in cases where
there fewer reducers than buckets.  



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