ClickHouse/tests/integration/test_mutation_fetch_fallback/test.py

import pytest

from helpers.cluster import ClickHouseCluster

cluster = ClickHouseCluster(__file__)

node1 = cluster.add_instance("node1", with_zookeeper=True)
node2 = cluster.add_instance("node2", with_zookeeper=True, stay_alive=True)


@pytest.fixture(scope="module")
def start_cluster():
    try:
        cluster.start()
        for ix, node in enumerate([node1, node2]):
            node.query_with_retry(
                """CREATE TABLE fetch_fallback (k int, v int, z String)
                ENGINE = ReplicatedMergeTree('/clickhouse/tables/test/t0', '{}')
                ORDER BY tuple()""".format(
                    ix
                )
            )
        yield cluster

    finally:
        cluster.shutdown()


def test_mutation_fetch_fallback(start_cluster):
    node1.query("INSERT INTO fetch_fallback(k, v) VALUES (1, 3), (2, 7), (3, 4)")

    node2.stop_clickhouse()

    # Run a mutation using non-deterministic `hostName` function to produce
    # different results on replicas and exercise the code responsible for
    # discarding local mutation results and fetching "byte-identical" parts
    # instead from the replica which first committed the mutation.
    node1.query(
        "ALTER TABLE fetch_fallback UPDATE z = hostName() WHERE 1 = 1",
        settings={"mutations_sync": 1, "allow_nondeterministic_mutations": 1},
    )

    node2.start_clickhouse()
    node1.query("SYSTEM SYNC REPLICA fetch_fallback", timeout=10)
    node2.query("SYSTEM SYNC REPLICA fetch_fallback", timeout=10)

    assert node2.contains_in_log(
        "We will download merged part from replica to force byte-identical result."
    )