If they are defined, they can override table-level settings.
{
    auto txn = local_context->getCurrentTransaction();
    DataPartsVector res;
    {
        auto lock = lockParts();
        for (const auto & partition_id : partition_ids)
        {
            DataPartStateAndPartitionID active_parts{MergeTreeDataPartState::Active, partition_id};
            insertAtEnd(
                res,
                DataPartsVector(
                    data_parts_by_state_and_info.lower_bound(active_parts),
                    data_parts_by_state_and_info.upper_bound(active_parts)));
            if (txn)
            {
                DataPartStateAndPartitionID outdated_parts{MergeTreeDataPartState::Active, partition_id};
                insertAtEnd(
                    res,
                    DataPartsVector(
                        data_parts_by_state_and_info.lower_bound(outdated_parts),
                        data_parts_by_state_and_info.upper_bound(outdated_parts)));
            }
        }
    }
    if (txn)
        filterVisibleDataParts(res, txn->getSnapshot(), txn->tid);
    return res;
}
MergeTreeData::DataPartPtr MergeTreeData::getPartIfExists(const MergeTreePartInfo & part_info, const MergeTreeData::DataPartStates & valid_states)