**How to reproduce**
Clickhouse server 20.13.1.5273
```
CREATE TABLE default.test
(
`key` UInt32,
`ts` DateTime CODEC(DoubleDelta, LZ4),
`db_time` DateTime DEFAULT now() COMMENT 'spout-ignore' CODEC(DoubleDelta, LZ4)
)
ENGINE = MergeTree
PARTITION BY toStartOfTenMinutes(db_time)
ORDER BY (key, ts)
TTL db_time + toIntervalHour(3)
SETTINGS index_granularity = 8192, merge_with_ttl_timeout = 3600, min_rows_for_compact_part = 1000000, min_bytes_for_compact_part = 200000000, in_memory_parts_enable_wal = 0;


INSERT INTO test(key, ts) SELECT number % 1000, now() + intDiv(number,1000) FROM numbers(500);

SELECT * FROM test;
500 rows in set. Elapsed: 0.003 sec.

DETACH TABLE test;

ATTACH TABLE test;

SELECT * FROM test;

0 rows in set. Elapsed: 0.002 sec.
```

**Expected behavior**
Clickhouse would flush parts on disk.
{
        metadata.set(std::make_unique<StorageInMemoryMetadata>(metadata_));
    }
    
    
    
    
    
    
    
    
    
    
    virtual NamesAndTypesList getVirtuals() const;
    Names getAllRegisteredNames() const override;
    NameDependencies getDependentViewsByColumn(ContextPtr context) const;
    
    virtual BackupEntries backup(const ASTs & partitions, ContextPtr context);
    
    virtual RestoreDataTasks restoreFromBackup(const BackupPtr & backup, const String & data_path_in_backup, const ASTs & partitions, ContextMutablePtr context);
protected:
    
    
    bool isVirtualColumn(const String & column_name, const StorageMetadataPtr & metadata_snapshot) const;
private:
    StorageID storage_id;
    mutable std::mutex id_mutex;