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From "Kadir OZDEMIR (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PHOENIX-5156) Consistent Mutable Global Indexes for Non-Transactional Tables
Date Sun, 14 Apr 2019 19:11:00 GMT

    [ https://issues.apache.org/jira/browse/PHOENIX-5156?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16817420#comment-16817420
] 

Kadir OZDEMIR commented on PHOENIX-5156:
----------------------------------------

You got it right. Not only two batches of mutations need to arrive on the same millisecond
for at least one common row but also the one acquiring the row locks first needs to take on
average less than 0.5ms (at most 1ms) to prepare the index mutations.

 
Assume that two batches of mutations concurrently want to update the same row X and plus some
other rows on the data table. One of them, batch 1, acquires the row locks for its rows and
the other, batch 2, is waiting for the row lock for X.
 
Batch 1 goes ahead and prepares the index updates for its rows blazingly fast and finishes
this in less than 1ms (I think this will be a very rare event) . It releases the row locks
to do the RPC calls for index updates (i.e., the first write phase). 
 
Batch 2 now acquires its locks in the same ms and uses the same timestamp as batch 1 did.
 
As you can see, the order in which the updates happens on row X on the data table can be different
than that on an index table in this case. Since these updates use the same timestamp, HBase
cannot order them correctly.
 
The solution I suggested for this problem is that Mutation 1 detects that the current ms is
the same as the ms just before the index update preparation, and thus, sleeps for 1ms before
releasing the row locks so that Mutation 2 gets a different timestamp. 

> Consistent Mutable Global Indexes for Non-Transactional Tables
> --------------------------------------------------------------
>
>                 Key: PHOENIX-5156
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-5156
>             Project: Phoenix
>          Issue Type: Bug
>    Affects Versions: 4.13.0, 4.14.0, 5.0.0, 4.14.1
>            Reporter: Kadir OZDEMIR
>            Assignee: Kadir OZDEMIR
>            Priority: Major
>         Attachments: PHOENIX-5156.master.001.patch, PHOENIX-5156.master.002.patch, PHOENIX-5156.master.003.patch,
PHOENIX-5156.master.004.patch, PHOENIX-5156.master.005.patch, PHOENIX-5156.master.006.patch,
PHOENIX-5156.master.007.patch, PHOENIX-5156.master.008.patch
>
>          Time Spent: 8h
>  Remaining Estimate: 0h
>
> Without transactional tables, the mutable global indexes can get easily out of sync with
their data tables in Phoenix. Transactional tables require a separate transaction manager,
have some restrictions and performance penalties. This issue is to have consistent mutable
global indexes without the need for using transactional tables.



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