PostgreSQLCopyHelper: copyHelper.SaveAll deadlocks

Description It appears that I am getting a deadlock when calling copyHelper.SaveAll(connection, tableEntities);. The same data inserts without a problem when I use an INSERT command. The SaveAll deadlocks whether I’m attempting to insert 1 or a million records. It even deadlocks when I attempt to SaveAll with an empty collection of tableEntities.

Environment Windows 10 Enterprise .NET 4.8 PostgreSQL 12 WPF application C#

To Reproduce My copyHelper looks like this:

            var copyHelper = new PostgreSQLCopyHelper<TableEntity>("MY_TABLE")
                .UsePostgresQuoting(true)
                .MapUUID("HARVEST_ID", x => x.HarvestGuid)
                .MapVarchar("OWNER", x => x.Owner)
                .MapVarchar("NAME", x => x.Name);

TableEntity is simply this:

    public class TableEntity
    {
        public Guid HarvestGuid { get; set; }
        public string Owner { get; set; }
        public string Name { get; set; }
    }

and tableEntities is:

            List<TableEntity> tableEntities = new List<TableEntity>();

To insert the records, the following code is executed:

        public bool InsertTables(Guid harvestGuid, DataTable dt)
        {
            if (!DataStoreReady)
                return false;

            if (dt == null || dt.Rows.Count == 0)
                return true;

            // prepare the data for insertion.
            var copyHelper = new PostgreSQLCopyHelper<TableEntity>("MY_TABLE")
                .UsePostgresQuoting(true)
                .MapUUID("HARVEST_ID", x => x.HarvestGuid)
                .MapVarchar("OWNER", x => x.Owner)
                .MapVarchar("NAME", x => x.Name);
                
            List<TableEntity> tableEntities = new List<TableEntity>();

            //brute force...
            foreach(DataRow row in dt.Rows)
            {
                TableEntity t = new TableEntity();

                t.HarvestGuid = harvestGuid;
                t.Owner = row["OWNER"].ToString();
                t.Name = row["TABLE_NAME"].ToString();

                tableEntities.Add(t);
            }

            try
            {

                using (NpgsqlConnection conn = new NpgsqlConnection(_connectionString.ConnectionString))
                {
                    conn.Open();

                    Logger.Debug("Beginning insertion of TABLE records.");

                    copyHelper.SaveAll(conn, tableEntities);  // <-- here is where the code deadlocks.

                    Logger.Debug("Completed insertion of TABLE records.");

                }
                return true;
            }
            catch (Exception ex)
            {
                Logger.Error("An exception was thrown while attempting to insert harvest inforamtion.");
                Logger.Error(ex);
                return false;
            }
        }

Expected behavior I expect the records to be inserted into the table.

Desktop (please complete the following information): Windows 10 Enterprise

Additional context I’ve tried this with 10,000 records, 1 record, even 0 records in the tableEntities list, but it always locks up. No exception is thrown. This is all executing on the UI thread.