22.2.1.4422.

```
create table test_alias (K Int64, D Date, S String, B Int64 Alias length(S)) Engine=MergeTree order by K;
insert into test_alias select number, today(), 'sdfsdfsdfsdfsdfds' from numbers(10000000);

session1: 
clickhouse-benchmark -c 10 <<< "insert into test_alias select number, today(), 'sdfsdfsdfsdfsdfds' from numbers(10000)"

session2: 
alter table test_alias drop column B;
0 rows in set. Elapsed: 251.043 sec.
```

especially it can be a problem with S3 disks

Alias columns do not persist in parts even in columns.txt
command.codec = ast_col_decl.codec;
        }
        if (command_ast->column)
            command.after_column = getIdentifierName(command_ast->column);
        if (ast_col_decl.ttl)
            command.ttl = ast_col_decl.ttl;
        command.first = command_ast->first;
        command.if_not_exists = command_ast->if_not_exists;
        return command;
    }
    else if (command_ast->type == ASTAlterCommand::DROP_COLUMN)
    {
        AlterCommand command;
        command.ast = command_ast->clone();
        command.type = AlterCommand::DROP_COLUMN;
        command.column_name = getIdentifierName(command_ast->column);
        command.if_exists = command_ast->if_exists;
        if (command_ast->clear_column)
            command.clear = true;
        if (command_ast->partition)
            command.partition = command_ast->partition;
        return command;
    }
    else if (command_ast->type == ASTAlterCommand::MODIFY_COLUMN)
    {
        AlterCommand command;
        command.ast = command_ast->clone();
        command.type = AlterCommand::MODIFY_COLUMN;
        const auto & ast_col_decl = command_ast->col_decl->as<ASTColumnDeclaration &>();
        command.column_name = ast_col_decl.name;