**Describe the bug**
```
5828589:2021.04.27 03:13:08.824665 [ 6101 ] {} <Trace> test_27.concurrent_alter_add_drop_3 (825021f7-129f-4841-ad6b-92215e3f1a94): Renaming temporary part tmp_merge_all_0_4_7_17 to all_0_4_7_17.
5828590:2021.04.27 03:13:08.824778 [ 3358 ] {} <Trace> test_27.concurrent_alter_add_drop_2 (f0a064d0-dc89-4710-9781-a49bb0c16461): Renaming temporary part tmp_merge_all_0_4_7_17 to all_0_4_7_17.
5828591:2021.04.27 03:13:08.824823 [ 6101 ] {} <Warning> test_27.concurrent_alter_add_drop_3 (825021f7-129f-4841-ad6b-92215e3f1a94): Tried to add obsolete part all_0_4_7_17 covered by all_0_4_13_34 (state Committed)
5828623:2021.04.27 03:13:08.824951 [ 3358 ] {} <Warning> test_27.concurrent_alter_add_drop_2 (f0a064d0-dc89-4710-9781-a49bb0c16461): Tried to add obsolete part all_0_4_7_17 covered by all_0_4_13_34 (state Committed)
5828624:2021.04.27 03:13:08.824995 [ 6101 ] {} <Warning> test_27.concurrent_alter_add_drop_3 (825021f7-129f-4841-ad6b-92215e3f1a94) (MergerMutator): Unexpected number of parts removed when adding all_0_4_7_17: 0 instead of 1
5828625:2021.04.27 03:13:08.825147 [ 3358 ] {} <Warning> test_27.concurrent_alter_add_drop_2 (f0a064d0-dc89-4710-9781-a49bb0c16461) (MergerMutator): Unexpected number of parts removed when adding all_0_4_7_17: 0 instead of 1
5828643:2021.04.27 03:13:08.831273 [ 3358 ] {} <Trace> test_27.concurrent_alter_add_drop_2 (f0a064d0-dc89-4710-9781-a49bb0c16461): Trying to immediately remove part all_0_4_7_17 (state Temporary)
5828644:2021.04.27 03:13:08.831658 [ 3358 ] {} <Fatal> : Logical error: 'Part all_0_4_7_17 doesn't exist'.
5828648:2021.04.27 03:13:08.832767 [ 6101 ] {} <Trace> test_27.concurrent_alter_add_drop_3 (825021f7-129f-4841-ad6b-92215e3f1a94): Trying to immediately remove part all_0_4_7_17 (state Temporary)
5828649:2021.04.27 03:13:08.833210 [ 6101 ] {} <Fatal> : Logical error: 'Part all_0_4_7_17 doesn't exist'.

```

https://clickhouse-test-reports.s3.yandex.net/0/9bb4d8769f1064ada4cce6b26d8ff61c11356965/stress_test_(debug).html#fail1
if (old_metadata.hasSortingKey())
    {
        
        
        Names new_primary_key_columns = new_primary_key.column_names;
        Names new_sorting_key_columns = new_sorting_key.column_names;
        ASTPtr added_key_column_expr_list = std::make_shared<ASTExpressionList>();
        const auto & old_sorting_key_columns = old_metadata.getSortingKeyColumns();
        for (size_t new_i = 0, old_i = 0; new_i < sorting_key_size; ++new_i)
        {
            if (old_i < old_sorting_key_columns.size())
            {
                if (new_sorting_key_columns[new_i] != old_sorting_key_columns[old_i])
                    added_key_column_expr_list->children.push_back(new_sorting_key.expression_list_ast->children[new_i]);
                else
                    ++old_i;
            }
            else
                added_key_column_expr_list->children.push_back(new_sorting_key.expression_list_ast->children[new_i]);
        }
        if (!added_key_column_expr_list->children.empty())
        {
            auto syntax = TreeRewriter(getContext()).analyze(added_key_column_expr_list, all_columns);
            Names used_columns = syntax->requiredSourceColumns();
            NamesAndTypesList deleted_columns;
            NamesAndTypesList added_columns;
            old_metadata.getColumns().getAllPhysical().getDifference(all_columns, deleted_columns, added_columns);
            for (const String & col : used_columns)
            {
                if (!added_columns.contains(col) || deleted_columns.contains(col))