Big decimals support

[DarkWanderer]

Big decimals support using custom type poached from public domain Planned features:

• Feature toggle to use regular decimal vs new class
• Type is convertible to normal numeric types and string

TODO

• [x] Fix all inaccuracies in math operations
• [ ] Do a round of optimizations
• [ ] Add config flag for supporting the new decimal
• [x] Implement parsing from text

Ref #137

[DmitryLk]

Hello! If I try to use ClickhouseDecimal as a Dapper parameter to Where. I get an exception "The member DecimalName of type ClickHouse.Client.Numerics.ClickHouseDecimal cannot be used as a parameter value".

    var connectionFactory = host.Services.GetService<IClickhouseConnectionFactory>()!;
    var text = @"
        SELECT *
        FROM xxxxxx.dapper_test2
        WHERE DecimalName = {DecimalName:decimal128(18)}
        ;
        ";

    var parameters = new Dictionary<string, object> { { "DecimalName", 
        new ClickHouseDecimal(BigInteger.Parse("123456789123123450000000000000"), 18)} };

    using var con = connectionFactory.GetConnection();

    var cmd = new CommandDefinition(text, parameters);
    try
    {
        var res = (await con.QueryAsync<DapperDto3>(cmd)).AsList();
    }
    catch (Exception e)
    {
        Console.WriteLine(e);
    }

[DmitryLk]

Hi! Scale parameter in new ClickhouseDecimal class can be positive only (ushort). Are you planning to do it also negative to suppot such cases as {mantissa:1, scale=-3} => 1000? Thank

[DarkWanderer]

@DmitryLk you need to add a custom type handler to Dapper to be able to handle the new Decimal:

Class definition:

        private class ClickHouseDecimalHandler : SqlMapper.TypeHandler<ClickHouseDecimal>
        {
            public override void SetValue(IDbDataParameter parameter, ClickHouseDecimal value) => parameter.Value = value.ToString(CultureInfo.InvariantCulture);

            public override ClickHouseDecimal Parse(object value) => value switch
            {
                ClickHouseDecimal chd => chd,
                IConvertible ic => Convert.ToDecimal(ic),
                _ => throw new ArgumentException(nameof(value))
            };
        }

After that, ClickHouseDecimal works both as parameter and as SELECTable value

            var parameters = new Dictionary<string, object> { { "value", new ClickHouseDecimal(1m) } };
            var results = await connection.QueryAsync<ClickHouseDecimal>("SELECT {value:Decimal32(3)}", parameters);
            Assert.AreEqual(value, results.Single());

[DarkWanderer]

Positive-only scale/exponent is by design right now as it matches ClickHouse's type. I'll think about switching back to possibly-negative exponent

[DmitryLk]

Thanks. ClickhouseDecimal parameter with custom handler to Dapper is working

[github-actions[bot]]

Package	Line Rate	Branch Rate	Complexity	Health
ClickHouse.Client	86%	74%	1036	✔
Summary	86% (1335 / 1561)	74% (471 / 640)	1036	✔

[github-actions[bot]]

Package	Line Rate	Branch Rate	Complexity	Health
ClickHouse.Client	86%	75%	1082	✔
Summary	86% (1423 / 1651)	75% (495 / 662)	1082	✔