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https://issues.apache.org/jira/browse/CASSANDRA-11223?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16095785#comment-16095785
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Stefania commented on CASSANDRA-11223:
--------------------------------------
The problem does not affect 2.2 because NamesQueryFilter.getLiveCount() is
unchanged, and in any case GroupByPrefix will count 1 live row if toGroup is
zero, which would be the case for the GroupByPrefix used by
NamesQueryFilter.columnCounter(). The queries on this type of tables will never
use SliceQueryFilter.
For 3.0+, it's a bit of a pain to revert, so I have created the follow-up
[patch|https://github.com/apache/cassandra/compare/trunk...stef1927:11223-3.0].
CI is currently running.
The patch ensures that static rows are always counted for static compact tables
(which is sufficient to fix the problem) but also assumes that a
NamesQueryFilter is selecting the entire partition if it has no clustering
values. This second part is not necessary but I think it's more correct because
in this case NamesQueryFilter is not restricting anything, and existing usages
of selectsAllPartition where limited to check if the filter restricts anything,
in order to create CQL string representations of a query.
Benjamin should be back in 1 week, but I can find a reviewer sooner if
required.
> 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
> Fix For: 2.2.11, 3.0.15, 3.11.1, 4.0
>
>
> 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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