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From "Benjamin Lerer (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-11223) Queries with LIMIT filtering on clustering columns can return less rows than expected
Date Tue, 04 Jul 2017 09:13:00 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-11223?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16073368#comment-16073368
] 

Benjamin Lerer commented on CASSANDRA-11223:
--------------------------------------------

I had a discussion with [~slebresne] one year ago about the static row filtering and we both
agreed that we should fix that behavior. Unfortunately, I did not do it straight away and
forgot about it.
Now, my understanding is that those problems should be fixed by CASSANDRA-8272. [~adelapena]
will those problems be solved by your patches for CASSANDRA-8272?

> Queries with LIMIT filtering on clustering columns can return less rows than expected
> -------------------------------------------------------------------------------------
>
>                 Key: CASSANDRA-11223
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-11223
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Local Write-Read Paths
>            Reporter: Benjamin Lerer
>            Assignee: Benjamin Lerer
>
> A query like {{SELECT * FROM %s WHERE b = 1 LIMIT 2 ALLOW FILTERING}} can return less
row than expected if the table has some static columns and some of the partition have no rows
matching b = 1.
> The problem can be reproduced with the following unit test:
> {code}
>     public void testFilteringOnClusteringColumnsWithLimitAndStaticColumns() throws
Throwable
>     {
>         createTable("CREATE TABLE %s (a int, b int, s int static, c int,
primary key (a, b))");
>         for (int i = 0; i < 3; i++)
>         {
>             execute("INSERT INTO %s (a, s) VALUES (?, ?)", i,
i);
>                 for (int j = 0; j < 3; j++)
>                     if (!(i == 0 && j
== 1))
>                         execute("INSERT
INTO %s (a, b, c) VALUES (?, ?, ?)", i, j, i + j);
>         }
>         assertRows(execute("SELECT * FROM %s"),
>                    row(1, 0, 1, 1),
>                    row(1, 1, 1, 2),
>                    row(1, 2, 1, 3),
>                    row(0, 0, 0, 0),
>                    row(0, 2, 0, 2),
>                    row(2, 0, 2, 2),
>                    row(2, 1, 2, 3),
>                    row(2, 2, 2, 4));
>         assertRows(execute("SELECT * FROM %s WHERE b = 1 ALLOW FILTERING"),
>                    row(1, 1, 1, 2),
>                    row(2, 1, 2, 3));
>         assertRows(execute("SELECT * FROM %s WHERE b = 1 LIMIT 2 ALLOW
FILTERING"),
>                    row(1, 1, 1, 2),
>                    row(2, 1, 2, 3)); // <--------
FAIL It returns only one row because the static row of partition 0 is counted and filtered
out in SELECT statement
>     }
> {code}



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