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From Andrés de la Peña (JIRA) <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-8272) 2ndary indexes can return stale data
Date Tue, 10 Jul 2018 19:42:00 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-8272?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16539153#comment-16539153
] 

Andrés de la Peña commented on CASSANDRA-8272:
----------------------------------------------

I have just rebased [the patch|https://github.com/adelapena/cassandra/commit/07e228824fb0e4ea04bf0b1ed11b347ce654f02a] with
some fixes for indexes on static columns. I have also added a few extra checks to [the dtests|https://github.com/apache/cassandra-dtest/compare/master...adelapena:CASSANDRA-8272].

> 2ndary indexes can return stale data
> ------------------------------------
>
>                 Key: CASSANDRA-8272
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-8272
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Sylvain Lebresne
>            Assignee: Andrés de la Peña
>            Priority: Major
>             Fix For: 3.0.x
>
>
> When replica return 2ndary index results, it's possible for a single replica to return
a stale result and that result will be sent back to the user, potentially failing the CL contract.
> For instance, consider 3 replicas A, B and C, and the following situation:
> {noformat}
> CREATE TABLE test (k int PRIMARY KEY, v text);
> CREATE INDEX ON test(v);
> INSERT INTO test(k, v) VALUES (0, 'foo');
> {noformat}
> with every replica up to date. Now, suppose that the following queries are done at {{QUORUM}}:
> {noformat}
> UPDATE test SET v = 'bar' WHERE k = 0;
> SELECT * FROM test WHERE v = 'foo';
> {noformat}
> then, if A and B acknowledge the insert but C respond to the read before having applied
the insert, then the now stale result will be returned (since C will return it and A or B
will return nothing).
> A potential solution would be that when we read a tombstone in the index (and provided
we make the index inherit the gcGrace of it's parent CF), instead of skipping that tombstone,
we'd insert in the result a corresponding range tombstone.  



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