**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.
std::optional<MergeTreeMutationStatus> getIncompleteMutationsStatus(Int64 mutation_version, std::set<String> * mutation_ids = nullptr) const;
    void startBackgroundMovesIfNeeded() override;
    std::unique_ptr<MergeTreeSettings> getDefaultSettings() const override;
    friend class MergeTreeProjectionBlockOutputStream;
    friend class MergeTreeSink;
    friend class MergeTreeData;
    friend class MergePlainMergeTreeTask;
    friend class MutatePlainMergeTreeTask;
protected:
    /** Attach the table with the appropriate name, along the appropriate path (with / at the end),
      *  (correctness of names and paths are not checked)
      *  consisting of the specified columns.
      *
      * See MergeTreeData constructor for comments on parameters.
      */
    StorageMergeTree(
        const StorageID & table_id_,
        const String & relative_data_path_,
        const StorageInMemoryMetadata & metadata,
        bool attach,
        ContextMutablePtr context_,
        const String & date_column_name,
        const MergingParams & merging_params_,
        std::unique_ptr<MergeTreeSettings> settings_,
        bool has_force_restore_data_flag);
    MutationCommands getFirstAlterMutationCommandsForPart(const DataPartPtr & part) const override;
};
}