ClickHouse/tests/performance/merge_table_streams.xml

<test>
<settings>
    <max_threads>5</max_threads>
    <allow_deprecated_syntax_for_merge_tree>1</allow_deprecated_syntax_for_merge_tree>
</settings>

<!-- Create four empty tables. We will test select from Merge table involving one real table and four empty tables. 
     In previous ClickHouse versions, with max_threads = 5, only one stream will be requested from each table,
      and the query will be processed with just one thread.
  -->
<create_query>CREATE TABLE merge_table_streams_1 AS hits_100m_single</create_query>
<create_query>CREATE TABLE merge_table_streams_2 AS hits_100m_single</create_query>
<create_query>CREATE TABLE merge_table_streams_3 AS hits_100m_single</create_query>
<create_query>CREATE TABLE merge_table_streams_4 AS hits_100m_single</create_query>

<query>SELECT UserID FROM merge(default, '^(hits_100m_single|merge_table_streams_\\d)$') WHERE UserID = 12345678901234567890</query>

<drop_query>DROP TABLE merge_table_streams_1</drop_query>
<drop_query>DROP TABLE merge_table_streams_2</drop_query>
<drop_query>DROP TABLE merge_table_streams_3</drop_query>
<drop_query>DROP TABLE merge_table_streams_4</drop_query>

</test>