If they are defined, they can override table-level settings.
#include <algorithm>
#include <iomanip>
#include <optional>
#include <set>
#include <thread>
#include <typeinfo>
#include <typeindex>
#include <unordered_set>
#include <filesystem>
namespace fs = std::filesystem;
namespace ProfileEvents
{
    extern const Event RejectedInserts;
    extern const Event DelayedInserts;
    extern const Event DelayedInsertsMilliseconds;
    extern const Event DuplicatedInsertedBlocks;
}
namespace CurrentMetrics
{
    extern const Metric DelayedInserts;
}
namespace
{
    constexpr UInt64 RESERVATION_MIN_ESTIMATION_SIZE = 1u * 1024u * 1024u; 
}
namespace DB
{
namespace ErrorCodes
{
    extern const int NO_SUCH_DATA_PART;