Throw on ordinary db engine

src/Databases/DatabaseOrdinary.cpp

@@ -80,6 +80,10 @@ void DatabaseOrdinary::convertMergeTreeToReplicatedIfNeeded(ASTPtr ast, const Qu
     if (!fs::exists(convert_to_replicated_flag_path))
         return;
 
+    if (getUUID() == UUIDHelpers::Nil)
+        throw Exception(ErrorCodes::NOT_IMPLEMENTED,
+            "Table engine conversion to replicated is supported only for Atomic databases. Convert your database engine to Atomic first.");
+
     LOG_INFO(log, "Found convert_to_replicated flag for table {}. Will try to change it's engine in metadata to replicated table.", backQuote(qualified_name.getFullName()));
 
     /// Get storage definition

tests/integration/test_modify_engine_on_restart/test_ordinary.py

@@ -0,0 +1,106 @@
+import pytest
+from helpers.cluster import ClickHouseCluster
+
+cluster = ClickHouseCluster(__file__)
+ch1 = cluster.add_instance(
+    "ch1",
+    main_configs=[
+        "configs/config.d/clusters.xml",
+        "configs/config.d/distributed_ddl.xml",
+    ],
+    with_zookeeper=True,
+    macros={"replica": "node1"},
+    stay_alive=True,
+)
+
+database_name = "modify_engine_on_ordinary"
+
+
+@pytest.fixture(scope="module")
+def started_cluster():
+    try:
+        cluster.start()
+        yield cluster
+
+    finally:
+        cluster.shutdown()
+
+
+def q(node, query):
+    return node.query(database=database_name, sql=query)
+
+def create_tables():
+    q(
+        ch1,
+        "CREATE TABLE mt ( A Int64, D Date, S String ) ENGINE MergeTree() PARTITION BY toYYYYMM(D) ORDER BY A;",
+    )
+
+def check_tables():
+    # Check tables exists
+    assert (
+        q(
+            ch1,
+            "SHOW TABLES",
+        ).strip()
+        == "mt"
+    )
+
+    # Check engines
+    assert (
+        q(
+            ch1,
+            f"SELECT name, engine FROM system.tables WHERE database = '{database_name}'",
+        ).strip()
+        == f"mt\tMergeTree"
+    )
+
+
+def set_convert_flags():
+    ch1.exec_in_container(
+        [
+            "bash",
+            "-c",
+            f"mkdir /var/lib/clickhouse/data/{database_name}/mt/flags",
+        ]
+    )
+    ch1.exec_in_container(
+        [
+            "bash",
+            "-c",
+            f"touch /var/lib/clickhouse/data/{database_name}/mt/flags/convert_to_replicated",
+        ]
+    )
+
+def remove_convert_flags():
+    ch1.exec_in_container(
+        [
+            "bash",
+            "-c",
+            f"rm -rf /var/lib/clickhouse/data/{database_name}/mt/flags",
+        ]
+    )
+
+def test_modify_engine_on_restart_ordinary_database(started_cluster):
+    ch1.query(
+        sql=f"CREATE DATABASE {database_name} ENGINE = Ordinary",
+        settings={"allow_deprecated_database_ordinary": 1},
+    )
+
+    create_tables()
+
+    check_tables()
+
+    set_convert_flags()
+
+    cannot_start = False
+    try:
+        ch1.restart_clickhouse()
+    except:
+        cannot_start = True
+    assert cannot_start
+
+    remove_convert_flags()
+
+    ch1.restart_clickhouse()
+
+    check_tables()