[jira] [Created] (CASSANDRA-16307) GROUP BY queries with paging can return deleted data

["Andres de la Peña (Jira)" <ji...@apache.org>]

Andres de la Peña created CASSANDRA-16307:
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             Summary: 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


{{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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