Support Async methods in ClickHouseConnection and ClickHouseCommand

Description

Propose to support async operations in implementation of ClickHouseConnection, ClickHouseCommand. It should be easy as long as it uses TcpClient under the hood.

What should be done

We can add methods OpenAsync, ConnectAsync, ExecuteNonQueryAsync and other methods as its done in System.Data.Common.DbConnection, System.Data.Common.DbCommand. In async implementation we can use existing SslStream.AuthenticateAsClient, await TcpClient.ConnectAsync and others.

[mikhail-novikov-mindbox]

Thanks for your answers! I will think about using ClickHouse.Client or creating PR to this one.

[VitaliyMF]

I’m not @killwort but it is not much sense to have async ADO.NET implementation for ClickHouse. This doesn’t give any significant benefits, at the same time async code may easily add hardly-reproducible issues.

ClickHouse is used for OLAP queries, and they rarely take less then hundreds ms. CH is not a transactional DB, it is not designed for many-many concurrent connections. If you have 100 concurrent queries, that’s already may be a problem for CH. At the same time, 100 locked threads (because of synchronous implementation) is a not a big deal for web app.

If you have many similar queries to CH, it makes sense simply to organize a cache on .NET side.