2020.07.10 07:51:57.119153 [ 35 ] {} <Error> DB.TABLE (ReplicatedMergeTreeAlterThread): void DB::ReplicatedMergeTreeAlterThread::run(): Code: 345, e.displayText() = DB::Exception: Suspiciously many (130) files
....
Aborting just in case. If it is not an error, you could increase merge_tree/max_files_to_remove_in_alter_columns parameter in configuration file (current value: 50), Stack trace (when copying this message, always include the lines below):

0. 0x1033ddd0 Poco::Exception::Exception(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, int)  in /usr/bin/clickhouse
1. 0x8ea95cd DB::Exception::Exception(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, int)  in /usr/bin/clickhouse
2. 0xd80e775 ?  in /usr/bin/clickhouse
3. 0xd974914 DB::ReplicatedMergeTreeAlterThread::run()  in /usr/bin/clickhouse
4. 0xcf60925 DB::BackgroundSchedulePoolTaskInfo::execute()  in /usr/bin/clickhouse
5. 0xcf60f42 DB::BackgroundSchedulePool::threadFunction()  in /usr/bin/clickhouse
6. 0xcf61080 ?  in /usr/bin/clickhouse
7. 0x8eccf9b ThreadPoolImpl<std::__1::thread>::worker(std::__1::__list_iterator<std::__1::thread, void*>)  in /usr/bin/clickhouse
8. 0x8ecb3a3 ?  in /usr/bin/clickhouse
9. 0x76ba start_thread  in /lib/x86_64-linux-gnu/libpthread-2.23.so
10. 0x10741d __clone  in /lib/x86_64-linux-gnu/libc-2.23.so
(version 20.1.11.73 (official build))

SELECT *
FROM system.merge_tree_settings
WHERE name = 'max_files_to_modify_in_alter_columns'

┌─name─────────────────────────────────┬─value─┬─changed─┬─description─────────────────────────────────────────────────────────────────────────────┐
│ max_files_to_modify_in_alter_columns │ 200   │       1 │ Not apply ALTER if number of files for modification(deletion, addition) more than this. │
└──────────────────────────────────────┴───────┴─────────┴─────────────────────────────────────────────────────────────────────────────────────────┘

query = 'select count(*) from {database}.{table}'
for i in res:
    client.execute(query.format(**i))