Change the table comment after created the table is not supported now?
Like mysql : ALTER TABLE [tableName] COMMNET [comment]; 
The sql "ALTER TABLE `system`.tables UPDATE Comment='test' WHERE NAME='t1';" also not supported!!!
My version is '21.9.4.35'。
ContextPtr local_context, const StorageMetadataPtr & metadata_snapshot, const ASTPtr & query_ptr) const
{
    ClusterPtr cluster = getCluster();
    const Settings & settings = local_context->getSettingsRef();
    bool sharding_key_is_usable = settings.allow_nondeterministic_optimize_skip_unused_shards || sharding_key_is_deterministic;
    if (has_sharding_key && sharding_key_is_usable)
    {
        ClusterPtr optimized = skipUnusedShards(cluster, query_ptr, metadata_snapshot, local_context);
        if (optimized)
            return optimized;
    }
    UInt64 force = settings.force_optimize_skip_unused_shards;
    if (force)
    {
        WriteBufferFromOwnString exception_message;
        if (!has_sharding_key)
            exception_message << "No sharding key";
        else if (!sharding_key_is_usable)
            exception_message << "Sharding key is not deterministic";
        else
            exception_message << "Sharding key " << sharding_key_column_name << " is not used";
        if (force == FORCE_OPTIMIZE_SKIP_UNUSED_SHARDS_ALWAYS)
            throw Exception(exception_message.str(), ErrorCodes::UNABLE_TO_SKIP_UNUSED_SHARDS);
        if (force == FORCE_OPTIMIZE_SKIP_UNUSED_SHARDS_HAS_SHARDING_KEY && has_sharding_key)
            throw Exception(exception_message.str(), ErrorCodes::UNABLE_TO_SKIP_UNUSED_SHARDS);
    }
    return {};
}
IColumn::Selector StorageDistributed::createSelector(const ClusterPtr cluster, const ColumnWithTypeAndName & result)