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https://issues.apache.org/jira/browse/CASSANDRA-11556?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15237329#comment-15237329
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Benjamin Lerer commented on CASSANDRA-11556:
--------------------------------------------
The {{LIMIT}} clause is used to filter the results returned to the user by
consequence it has no effect on an aggregate queries as they returns only one
result.
In my opinion, we should look at the {{PER PARTITION LIMIT}} in the same way,
meaning a limit on the results returned to the user. In which case it makes
sense to reject it for aggregate queries. I think it would be reasonable on the
other hand to support it with group by queries (CASSANDRA-10707) as the groups
are build at the partition level.
> PER PARTITION LIMIT does not work properly for multi-partition query with
> ORDER BY
> ----------------------------------------------------------------------------------
>
> Key: CASSANDRA-11556
> URL: https://issues.apache.org/jira/browse/CASSANDRA-11556
> Project: Cassandra
> Issue Type: Bug
> Reporter: Benjamin Lerer
> Assignee: Alex Petrov
> Fix For: 3.6
>
>
> Multi-partition queries with {{PER PARTITION LIMIT}} with {{ORDER BY}} do not
> respect the {{PER PARTITION LIMIT}}.
> The problem can be reproduced with the following unit test:
> {code}
> @Test
> public void testPerPartitionLimitWithMultiPartitionQueryAndOrderBy()
> throws Throwable
> {
> createTable("CREATE TABLE %s (a int, b int, c int, PRIMARY KEY (a,
> b))");
> for (int i = 0; i < 5; i++)
> {
> for (int j = 0; j < 5; j++)
> {
> execute("INSERT INTO %s (a, b, c) VALUES (?, ?, ?)", i, j, j);
> }
> }
> assertRows(execute("SELECT * FROM %s WHERE a IN (2, 3) ORDER BY b
> DESC PER PARTITION LIMIT ?", 2),
> row(2, 4, 4),
> row(3, 4, 4),
> row(2, 3, 3),
> row(3, 3, 3));
> }
> {code}
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