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From "Alex Petrov (JIRA)" <j...@apache.org>
Subject [jira] [Issue Comment Deleted] (CASSANDRA-8273) Allow filtering queries can return stale data
Date Tue, 16 May 2017 12:22:04 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-8273?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Alex Petrov updated CASSANDRA-8273:
-----------------------------------
    Comment: was deleted

(was: Should we start working on moving filtering to the coordinator right away, or should
we maybe wait for the {{QueryPlanner}} (which is at the moment not really planned)?)

> Allow filtering queries can return stale data
> ---------------------------------------------
>
>                 Key: CASSANDRA-8273
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-8273
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Sylvain Lebresne
>            Assignee: Andrés de la Peña
>
> Data filtering is done replica side. That means that a single replica with stale data
may make the whole query return that stale data.
> For instance, consider 3 replicas A, B and C, and the following situation:
> {noformat}
> CREATE TABLE test (k int PRIMARY KEY, v1 text, v2 int);
> CREATE INDEX ON test(v1);
> INSERT INTO test(k, v1, v2) VALUES (0, 'foo', 1);
> {noformat}
> with every replica up to date. Now, suppose that the following queries are done at {{QUORUM}}:
> {noformat}
> UPDATE test SET v2 = 2 WHERE k = 0;
> SELECT * FROM test WHERE v1 = 'foo' AND v2 = 1;
> {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. Let's note that this is a problem
related to filtering, not 2ndary indexes.
> This issue share similarity with CASSANDRA-8272 but contrarily to that former issue,
I'm not sure how to fix it. Obviously, moving the filtering to the coordinator would remove
that problem, but doing so would, on top of not being trivial to implmenent, have serious
performance impact since we can't know in advance how much data will be filtered and we may
have to redo query to replica multiple times.



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