**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.
}
    return {};
}
bool StorageMergeTree::scheduleDataProcessingJob(BackgroundJobsAssignee & assignee) 
{
    if (shutdown_called)
        return false;
    assert(!isStaticStorage());
    auto metadata_snapshot = getInMemoryMetadataPtr();
    std::shared_ptr<MergeMutateSelectedEntry> merge_entry, mutate_entry;
    bool were_some_mutations_skipped = false;
    auto share_lock = lockForShare(RWLockImpl::NO_QUERY, getSettings()->lock_acquire_timeout_for_background_operations);
    bool has_mutations = false;
    {
        std::unique_lock lock(currently_processing_in_background_mutex);
        if (merger_mutator.merges_blocker.isCancelled())
            return false;
        merge_entry = selectPartsToMerge(metadata_snapshot, false, {}, false, nullptr, share_lock, lock);
        if (!merge_entry)
            mutate_entry = selectPartsToMutate(metadata_snapshot, nullptr, share_lock, lock, were_some_mutations_skipped);
        has_mutations = !current_mutations_by_version.empty();
    }
    if ((!mutate_entry && has_mutations) || were_some_mutations_skipped)
    {
        
        
        std::lock_guard lock(mutation_wait_mutex);
        mutation_wait_event.notify_all();
    }
    if (merge_entry)