For some reasons when we delete a MergeTree Part in atomic way something may go wrong - and leave the `delete_tmp_*` folder or it's part on disk. This may lead to a disk space consumption over time.

It's suggested to delete this folders at least at server start-up. Current solution with `clearOldTemporaryDirectories()` doesn't work because this method is called periodically from a thread without any locks or advisory on folders - it may cause the race conditions.
alter_entry.emplace();
        mutation_znode.reset();
        auto current_metadata = getInMemoryMetadataPtr();
        StorageInMemoryMetadata future_metadata = *current_metadata;
        commands.apply(future_metadata, query_context);
        ReplicatedMergeTreeTableMetadata future_metadata_in_zk(*this, current_metadata);
        if (ast_to_str(future_metadata.sorting_key.definition_ast) != ast_to_str(current_metadata->sorting_key.definition_ast))
        {
            
            
            
            
            future_metadata_in_zk.sorting_key = serializeAST(*extractKeyExpressionList(future_metadata.sorting_key.definition_ast));
        }
        if (ast_to_str(future_metadata.sampling_key.definition_ast) != ast_to_str(current_metadata->sampling_key.definition_ast))
            future_metadata_in_zk.sampling_expression = serializeAST(*extractKeyExpressionList(future_metadata.sampling_key.definition_ast));
        if (ast_to_str(future_metadata.partition_key.definition_ast) != ast_to_str(current_metadata->partition_key.definition_ast))
            future_metadata_in_zk.partition_key = serializeAST(*extractKeyExpressionList(future_metadata.partition_key.definition_ast));
        if (ast_to_str(future_metadata.table_ttl.definition_ast) != ast_to_str(current_metadata->table_ttl.definition_ast))
        {
            if (future_metadata.table_ttl.definition_ast)
                future_metadata_in_zk.ttl_table = serializeAST(*future_metadata.table_ttl.definition_ast);
            else 
                future_metadata_in_zk.ttl_table = "";
        }
        String new_indices_str = future_metadata.secondary_indices.toString();
        if (new_indices_str != current_metadata->secondary_indices.toString())
            future_metadata_in_zk.skip_indices = new_indices_str;
        String new_projections_str = future_metadata.projections.toString();