Does syntaxis exists to cast data types? about clickhouse-net

[killwort]

Nope, query parser in driver does not support such syntax.
By the way, you have control over parameter type/value, why do you need explicit cast?
And, as clickhouse documentation states, you shouldn't use one-row inserts, check info in https://github.com/killwort/ClickHouse-Net#hidden-bulk-insert-functionality here for more efficient way of inserting.

[RomanOlegovich]

@killwort
I want to import rows from Postgres

select OrderId, IsFirstOrder from orders

and export to ClickHouse

insert into FactOrder (OrderId, IsFirstOrder) values @bulk

Both database has boolean db type for IsFirstOrder.

But in c# code IsFirstOrder has different db types: Boolean in postgres and DbByte in clickhouse.

System.InvalidCastException: 'Unable to cast object of type 'System.Boolean' to type 'System.SByte'.'

Read from Postgres

                using (var dataReader = cmd.ExecuteReader())
                {
                    while (dataReader.Read())
                    {
                        var row = new Dictionary<string, object>();
                        for (var fieldCount = 0; fieldCount < dataReader.FieldCount; fieldCount++)
                        {
                            row.Add(dataReader.GetName(fieldCount), dataReader[fieldCount]);
                        }
                        yield return row;
                    }
                }

write to ClickHouse

            using (var cmd = db.CreateCommand())
            {
                cmd.CommandText = sql;
                if (cmd.Connection.State != ConnectionState.Open) { cmd.Connection.Open(); }

                if (@params != null)
                    foreach (KeyValuePair<string, object> p in @params)
                    {
                        IDbDataParameter dbParameter = cmd.CreateParameter();
                        dbParameter.ParameterName = p.Key;
                        dbParameter.Value = p.Value;
                        cmd.Parameters.Add(dbParameter);
                    }

                return cmd.ExecuteNonQuery();
            }

How I can cast postgres:boolean to clickhouse:boolean in this case?

[killwort]

When you implement IEnumerable interface in your object, do casts on return, like that:

  class MyDataObject:IEnumerable{
    public bool SomeBooleanFieldStoredInUInt8{get;set;}
    ....
    public IEnumerator GetEnumerator(){
      ....
      yield return SomeBooleanFieldStoredInUInt8?(byte)1:(byte)0;
      ....
    }
  }

[RomanOlegovich]

the idea is that all the code should be in sql, and c # does not know what data will be there, c # code can only call DbCommand for reading and writing.

[RomanOlegovich]

I think it may be a part of your sdk.
DBNull -> (object)null
Bool => sbyte