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Posted to commits@cassandra.apache.org by "Alex Petrov (Jira)" <ji...@apache.org> on 2021/02/02 16:26:00 UTC
[jira] [Commented] (CASSANDRA-16307) GROUP BY queries with paging
can return deleted data
[ https://issues.apache.org/jira/browse/CASSANDRA-16307?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17277259#comment-17277259 ]
Alex Petrov commented on CASSANDRA-16307:
-----------------------------------------
Good news: this is just an artifact of faulty pager in in-jvm dtests.
|[trunk patch|https://github.com/apache/cassandra/pull/884]|[CI|https://app.circleci.com/pipelines/github/ifesdjeen/cassandra?branch=16307-trunk]|
> GROUP BY queries with paging can return deleted data
> ----------------------------------------------------
>
> Key: CASSANDRA-16307
> URL: https://issues.apache.org/jira/browse/CASSANDRA-16307
> Project: Cassandra
> Issue Type: Bug
> Components: Consistency/Coordination
> Reporter: Andres de la Peña
> Assignee: Alex Petrov
> Priority: Normal
> Fix For: 3.11.x, 4.0-beta
>
>
> {{GROUP BY}} queries using paging and CL>ONE/LOCAL_ONE. This dtest reproduces the problem:
> {code:java}
> try (Cluster cluster = init(Cluster.create(2)))
> {
> cluster.schemaChange(withKeyspace("CREATE TABLE %s.t (pk int, ck int, PRIMARY KEY (pk, ck))"));
> ICoordinator coordinator = cluster.coordinator(1);
> coordinator.execute(withKeyspace("INSERT INTO %s.t (pk, ck) VALUES (0, 0)"), ConsistencyLevel.ALL);
> coordinator.execute(withKeyspace("INSERT INTO %s.t (pk, ck) VALUES (1, 1)"), ConsistencyLevel.ALL);
>
> cluster.get(1).executeInternal(withKeyspace("DELETE FROM %s.t WHERE pk=0 AND ck=0"));
> cluster.get(2).executeInternal(withKeyspace("DELETE FROM %s.t WHERE pk=1 AND ck=1"));
> String query = withKeyspace("SELECT * FROM %s.t GROUP BY pk");
> Iterator<Object[]> rows = coordinator.executeWithPaging(query, ConsistencyLevel.ALL, 1);
> assertRows(Iterators.toArray(rows, Object[].class));
> }
> {code}
> Using a 2-node cluster and RF=2, the test inserts two partitions in both nodes. Then it locally deletes each row in a separate node, so each node sees a different partition alive, but reconciliation should produce no alive partitions. However, a {{GROUP BY}} query using a page size of 1 wrongly returns one of the rows.
> This has been detected during CASSANDRA-16180, and it is probably related to CASSANDRA-15459, which solved a similar problem for group-by queries with limit, instead of paging.
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