If you have really wide table with many thousands of columns and you want to drop / modify column.
For wide parts it working fine, but for compact clickhouse would try to allocate a lot of memory and going to be killed via OOM killer.



**Does it reproduce on recent release?**

Yes, 21.9

**How to reproduce**
```
clickhouse-client -mn --query="SELECT 'CREATE TABLE xxx_really_wide( ' || arrayStringConcat(groupArray('column_'|| toString(number) || ' Nullable(UInt32)'), ',') || ') ENGINE=MergeTree ORDER BY assumeNotNull(column_0)' FROM numbers(6000) FORMAT TSVRaw" | clickhouse-client -mn

clickhouse-client -mn --query="SELECT arrayStringConcat(replicate('1', range(6000)), ',') FROM numbers(300) FORMAT TSVRaw" | clickhouse-client -mn --query "INSERT INTO xxx_really_wide FORMAT CSV " --send_logs_level='trace'
```

```
SELECT *
FROM system.merges
FORMAT Vertical

Query id: d9751847-a689-49f0-aab3-f868d9c08e34

Row 1:
──────
database:                    default
table:                       xxx_really_wide
elapsed:                     84.8952157
progress:                    0
num_parts:                   1
source_part_names:           ['all_1_1_0']
result_part_name:            all_1_1_0_3
source_part_paths:           ['/var/lib/clickhouse/data/default/xxx_really_wide/all_1_1_0/']
result_part_path:            /var/lib/clickhouse/data/default/xxx_really_wide/all_1_1_0_3/
partition_id:                all
is_mutation:                 1
total_size_bytes_compressed: 456027
total_size_marks:            2
bytes_read_uncompressed:     0
rows_read:                   0
bytes_written_uncompressed:  0
rows_written:                0
columns_written:             0
memory_usage:                16836533272
thread_id:                   16171
merge_type:
merge_algorithm:

Row 2:
──────
database:                    default
table:                       xxx_really_wide
elapsed:                     84.8947852
progress:                    0
num_parts:                   1
source_part_names:           ['all_2_2_0']
result_part_name:            all_2_2_0_3
source_part_paths:           ['/var/lib/clickhouse/data/default/xxx_really_wide/all_2_2_0/']
result_part_path:            /var/lib/clickhouse/data/default/xxx_really_wide/all_2_2_0_3/
partition_id:                all
is_mutation:                 1
total_size_bytes_compressed: 468027
total_size_marks:            2
bytes_read_uncompressed:     0
rows_read:                   0
bytes_written_uncompressed:  0
rows_written:                0
columns_written:             0
memory_usage:                16706294896
thread_id:                   16174
merge_type:
merge_algorithm:
```

const MutationCommand & command,
    const StoragePtr & storage,
    ContextPtr context
)
{
    ASTPtr partition_predicate_as_ast_func;
    if (command.partition)
    {
        String partition_id;
        auto storage_merge_tree = std::dynamic_pointer_cast<MergeTreeData>(storage);
        auto storage_from_merge_tree_data_part = std::dynamic_pointer_cast<StorageFromMergeTreeDataPart>(storage);
        if (storage_merge_tree)
            partition_id = storage_merge_tree->getPartitionIDFromQuery(command.partition, context);
        else if (storage_from_merge_tree_data_part)
            partition_id = storage_from_merge_tree_data_part->getPartitionIDFromQuery(command.partition, context);
        else
            throw Exception("ALTER UPDATE/DELETE ... IN PARTITION is not supported for non-MergeTree tables", ErrorCodes::NOT_IMPLEMENTED);
        partition_predicate_as_ast_func = makeASTFunction("equals",
                    std::make_shared<ASTIdentifier>("_partition_id"),
                    std::make_shared<ASTLiteral>(partition_id)
        );
    }
    if (command.predicate && command.partition)
        return makeASTFunction("and", command.predicate->clone(), std::move(partition_predicate_as_ast_func));
    else
        return command.predicate ? command.predicate->clone() : partition_predicate_as_ast_func;
}
MutationsInterpreter::MutationsInterpreter(