connection is already in state 'Executing' when inserting lots of objects [Using Dapper]

I submitted a report on the dapper repo for this issue as well. https://github.com/StackExchange/Dapper/issues/919

Steps to reproduce

Essentially, I have a bit of code that inserts rows into 2 tables. The second table has a Foreign Key to the first.

using (TransactionScope scope = new TransactionScope(TransactionScopeOption.Required, TransactionScopeAsyncFlowOption.Enabled))
{	
	const string query = @"WITH updated as (
					INSERT INTO public.schedule_row
					(id, schedule_id, petraid, ssnit, staffid, fullname, salary, total, created_by, validation_messages)
					VALUES
					(@Id, @ScheduleId, @PetraId, @Ssnit, @StaffId, @Fullname, @Salary, @Total, @ModifiedBy, @ValidationMessage)
				)
				UPDATE public.schedule
				SET
					is_valid = false
					,   updated_by = @ModifiedBy
					,   updated_at = now()
					,   validation_processed_at = NULL
					,   validation_reminders_count = 0
					,   validation_reminder_last_sent_at = NULL
				WHERE id = @ScheduleId;
			";

	var rows_ = rows.Select(sc =>
	{
		var total = sc.Contributions.Sum(c => string.IsNullOrWhiteSpace(c.Amount) ? 0 : Decimal.Parse(c.Amount));
		var salary = string.IsNullOrWhiteSpace(sc.Salary) ? 0 : Decimal.Parse(sc.Salary);

		var petraId = sc.PetraId?.ToUpper();
		petraId = petraId?.StartsWith("H1") ?? false ? petraId.Replace("H1", "HI") : petraId;
		return new
		{
			Id = NewId.NextGuid(),
			ScheduleId = scheduleId,
			PetraId = petraId,
			Ssnit = sc.Ssnit,
			StaffId = sc.StaffId,
			Fullname = sc.Fullname,
			Salary = salary,
			Total = total,
			ModifiedBy = modifiedBy,
			Contributions = sc.Contributions,
			ValidationMessage = new String[] { "Not validated yet" }
		};
	}).ToArray();

	var count = await conn.ExecuteAsync(query, rows_).ConfigureAwait(false);

	if (count > 0)
	{
		const string contributionsQuery = @"
				INSERT INTO public.schedule_row_contribution
				(schedule_row_id, deal_contribution_type, amount)
				VALUES
				(@ScheduleRowId, @DealContributionType, @Amount)
				ON CONFLICT (schedule_row_id, deal_contribution_type)
				DO NOTHING
			";

		var _rowContributions = rows_.SelectMany(r => r.Contributions.Select(c => new
		{
			ScheduleRowId = r.Id,
			DealContributionType = c.DealContributionType,
			Amount = string.IsNullOrWhiteSpace(c.Amount) ? 0 : Decimal.Parse(c.Amount),
		})).ToArray();
		await conn.ExecuteAsync(contributionsQuery, _rowContributions).ConfigureAwait(false);
	}
}

The issue

The code works find and we haven’t had any issues.

I noticed however that an exception is thrown when the number of rows being inserted into both tables is more than approximately 20k total. In my case, I had about 11244 items in each list.

I made sure all calls are awaited so I do not get promoted to a distributed transaction since this is net core 2.0.

I run tests where I split the rows into batches of 5000 in an attempt to test. The exception gets thrown at around the 3rd or 4th iteration.

I am totally stumped here. Any pointers?

Exception message: The connection is already in state 'Executing'
Stack trace:

Npgsql.NpgsqlOperationInProgressException: The connection is already in state 'Executing'
   at Npgsql.NpgsqlConnector.StartUserAction(ConnectorState newState, NpgsqlCommand command)
   at Npgsql.NpgsqlCommand.<ExecuteNonQuery>d__84.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Npgsql.NpgsqlCommand.<>c__DisplayClass83_0.<<ExecuteNonQueryAsync>b__0>d.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Dapper.SqlMapper.<ExecuteMultiImplAsync>d__36.MoveNext() in C:\projects\dapper\Dapper\SqlMapper.Async.cs:line 622
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.ConfiguredTaskAwaitable`1.ConfiguredTaskAwaiter.GetResult()

Further technical details

Npgsql version: 3.2.6 PostgreSQL version: 9.6 Operating system: Windows 10

Other details about my project setup: Net Core 2.0

[rudi-bruchez]

Let me anonymize it, I’ll send you some code to repro

[YohDeadfall]

Closing since no repro was posted back.