Statistics
https://play.clickhouse.com/play?user=play#c2VsZWN0IAp0b1N0YXJ0T2ZIb3VyKGNoZWNrX3N0YXJ0X3RpbWUpIGFzIGQsCmNvdW50KCksICBncm91cFVuaXFBcnJheShwdWxsX3JlcXVlc3RfbnVtYmVyKSwgIGFueShyZXBvcnRfdXJsKQpmcm9tIGNoZWNrcyB3aGVyZSAnMjAyMi0wNi0wMScgPD0gY2hlY2tfc3RhcnRfdGltZSBhbmQgdGVzdF9uYW1lIGxpa2UgJyUwMjQ5MV9wYXJ0X2xvZ19oYXNfdGFibGVfdXVpZCUnIGFuZCB0ZXN0X3N0YXR1cyBpbiAoJ0ZBSUwnLCAnRkxBS1knKSBncm91cCBieSBkIG9yZGVyIGJ5IGQgZGVzYw==

Some times there are not output from requests.
const StoragePtr & source_table, const StorageMetadataPtr & src_snapshot, const StorageMetadataPtr & my_snapshot) const
{
    return checkStructureAndGetMergeTreeData(*source_table, src_snapshot, my_snapshot);
}
std::pair<MergeTreeData::MutableDataPartPtr, scope_guard> MergeTreeData::cloneAndLoadDataPartOnSameDisk(
    const MergeTreeData::DataPartPtr & src_part,
    const String & tmp_part_prefix,
    const MergeTreePartInfo & dst_part_info,
    const StorageMetadataPtr & metadata_snapshot,
    const MergeTreeTransactionPtr & txn,
    HardlinkedFiles * hardlinked_files,
    bool copy_instead_of_hardlink,
    const NameSet & files_to_copy_instead_of_hardlinks)
{
    
    bool does_storage_policy_allow_same_disk = false;
    for (const DiskPtr & disk : getStoragePolicy()->getDisks())
    {
        if (disk->getName() == src_part->getDataPartStorage().getDiskName())
        {
            does_storage_policy_allow_same_disk = true;
            break;
        }