Correctly override default settings remotely

src/Core/Settings.h

@@ -353,7 +353,7 @@ class IColumn;
     M(Bool, allow_introspection_functions, false, "Allow functions for introspection of ELF and DWARF for query profiling. These functions are slow and may impose security considerations.", 0) \
     \
     M(UInt64, max_partitions_per_insert_block, 100, "Limit maximum number of partitions in single INSERTed block. Zero means unlimited. Throw exception if the block contains too many partitions. This setting is a safety threshold, because using large number of partitions is a common misconception.", 0) \
-    M(UInt64, max_partitions_to_read, 0, "Limit the max number of partitions that can be accessed in one query. 0 means unlimited.", 0) \
+    M(Int64, max_partitions_to_read, -1, "Limit the max number of partitions that can be accessed in one query. <= 0 means unlimited.", 0) \
     M(Bool, check_query_single_value_result, true, "Return check query result as single 1/0 value", 0) \
     M(Bool, allow_drop_detached, false, "Allow ALTER TABLE ... DROP DETACHED PART[ITION] ... queries", 0) \
     \

src/Storages/MergeTree/MergeTreeDataSelectExecutor.cpp

@@ -709,12 +709,12 @@ QueryPlanPtr MergeTreeDataSelectExecutor::readFromParts(
 
     auto max_partitions_to_read
         = settings.max_partitions_to_read.changed ? settings.max_partitions_to_read : data.getSettings()->max_partitions_to_read;
-    if (max_partitions_to_read)
+    if (max_partitions_to_read > 0)
     {
         std::set<String> partitions;
         for (auto & part_with_ranges : parts_with_ranges)
             partitions.insert(part_with_ranges.data_part->info.partition_id);
-        if (partitions.size() > max_partitions_to_read)
+        if (partitions.size() > size_t(max_partitions_to_read))
             throw Exception(
                 ErrorCodes::TOO_MANY_PARTITIONS,
                 "Too many partitions to read. Current {}, max {}",

src/Storages/MergeTree/MergeTreeSettings.h

@@ -110,7 +110,7 @@ struct Settings;
     M(Bool, allow_nullable_key, false, "Allow Nullable types as primary keys.", 0) \
     M(Bool, remove_empty_parts, true, "Remove empty parts after they were pruned by TTL, mutation, or collapsing merge algorithm", 0) \
     M(Bool, assign_part_uuids, false, "Generate UUIDs for parts. Before enabling check that all replicas support new format.", 0) \
-    M(UInt64, max_partitions_to_read, 0, "Limit the max number of partitions that can be accessed in one query. 0 means unlimited. This setting is the default that can be overridden by the query-level setting with the same name.", 0) \
+    M(Int64, max_partitions_to_read, -1, "Limit the max number of partitions that can be accessed in one query. <= 0 means unlimited. This setting is the default that can be overridden by the query-level setting with the same name.", 0) \
     \
     /** Obsolete settings. Kept for backward compatibility only. */ \
     M(UInt64, min_relative_delay_to_yield_leadership, 120, "Obsolete setting, does nothing.", 0) \

tests/integration/test_passing_max_partitions_to_read_remotely/test.py

@@ -0,0 +1,28 @@
+import pytest
+from helpers.cluster import ClickHouseCluster
+
+cluster = ClickHouseCluster(__file__)
+ch1 = cluster.add_instance("ch1")
+ch2 = cluster.add_instance("ch2")
+
+
+@pytest.fixture(scope="module")
+def started_cluster():
+    try:
+        cluster.start()
+        ch1.query("CREATE DATABASE test_default_database;")
+        yield cluster
+
+    finally:
+        cluster.shutdown()
+
+
+def test_default_database_on_cluster(started_cluster):
+    ch1.query(
+        database="test_default_database",
+        sql="CREATE TABLE test_local_table ENGINE MergeTree PARTITION BY i ORDER BY tuple() SETTINGS max_partitions_to_read = 1 AS SELECT arrayJoin([1, 2]) i;",
+    )
+
+    assert ch2.query(
+        sql="SELECT * FROM remote('ch1:9000', test_default_database, test_local_table) ORDER BY i FORMAT TSV SETTINGS max_partitions_to_read = 0;",
+    ) == "1\n2\n"