Method execute

src/Interpreters/InterpreterSystemQuery.cpp:344–1255

BlockIO InterpreterSystemQuery::execute()
{
    auto & query = query_ptr->as<ASTSystemQuery &>();

    if (!query.cluster.empty())
    {
        DDLQueryOnClusterParams params;
        params.access_to_check = getRequiredAccessForDDLOnCluster();
        return executeDDLQueryOnCluster(query_ptr, getContext(), params);
    }

    using Type = ASTSystemQuery::Type;

    /// Use global context with fresh system profile settings
    auto system_context = Context::createCopy(getContext()->getGlobalContext());
    /// Don't check for constraints when changing profile. It was accepted before (for example it might include
    /// some experimental settings)
    bool check_constraints = false;
    system_context->setCurrentProfile(getContext()->getSystemProfileName(), check_constraints);

    /// Make canonical query for simpler processing
    if (query.type == Type::RELOAD_DICTIONARY)
    {
        if (query.database)
            query.setTable(query.getDatabase() + "." + query.getTable());
    }
    else if (query.table)
    {
        StorageID id_in_query(query.getDatabase(), query.getTable());
        /// `IF EXISTS` (currently parsed for `SYSTEM SYNC REPLICA`) must suppress
        /// `UNKNOWN_DATABASE` in addition to `UNKNOWN_TABLE`. Plain `resolveStorageID`
        /// throws on a missing database before the per-handler `if_exists` check is
        /// reached, so use `tryResolveStorageID` here when `if_exists` is set.
        /// The handler still validates table existence via the catalog.
        if (query.if_exists)
            table_id = getContext()->tryResolveStorageID(id_in_query, Context::ResolveOrdinary);
        else
            table_id = getContext()->resolveStorageID(id_in_query, Context::ResolveOrdinary);
    }


    BlockIO result;

    volume_ptr = {};
    if (!query.storage_policy.empty() && !query.volume.empty())
        volume_ptr = getContext()->getStoragePolicy(query.storage_policy)->getVolumeByName(query.volume);

    switch (query.type)
    {
        case Type::SHUTDOWN:
        {
            getContext()->checkAccess(AccessType::SYSTEM_SHUTDOWN);
            if (kill(0, SIGTERM))
                throw ErrnoException(ErrorCodes::CANNOT_KILL, "System call kill(0, SIGTERM) failed");
            break;
        }
        case Type::KILL:
        {