ClickHouse/tests/performance/mmap_io.xml

<test>
    <settings>
        <local_filesystem_read_method>mmap</local_filesystem_read_method>
        <min_bytes_to_use_mmap_io>1</min_bytes_to_use_mmap_io>
    </settings>

    <create_query>CREATE TABLE hits_none (WatchID UInt64 CODEC(NONE)) ENGINE = MergeTree ORDER BY tuple()</create_query>
    <fill_query>INSERT INTO hits_none SELECT WatchID FROM test.hits</fill_query>
    <fill_query>OPTIMIZE TABLE hits_none FINAL</fill_query>

    <query short="1"><![CDATA[SELECT sum(WatchID) FROM hits_none]]></query>

    <drop_query>DROP TABLE hits_none</drop_query>
</test>