Output format support

Quite often all appication is doing is just feeding query result to a “processing pipeline” in some format (“returning json from rest api to some client, maybe some SPA” is not an exception here). As clickhouse already supports great variety of output formats that could be fed to the “pipeline” (json, protobuf, avro, arrow, parquet, csv) it looks reasonable to allow query results to be returned in desired format to cut ADO and formatting libraries all together. There can be an extension method on a reader object named, for example, “export”, accepting stream where data should be copied:

var command = connection.CreateCommand();
command.Text = ".... Format Protobuf";
using var reader = await command.ExecuteReaderAsync();
await reader.Export(output);

Another option is having extension method for command:

var command = connection.CreateCommand();
command.Text = ".... Format Protobuf";
using var exporter = await command.ExecuteExportAsync();
await exporter.Export(output);

It is important to separate query execution from “copying results” to be able to handle errors

[DarkWanderer]

Hi,

Added ExecuteRawResultAsync function, example:

            using var command = connection.CreateCommand();
            command.CommandText = "SELECT 1 FORMAT TSV";
            using var result = await command.ExecuteRawResultAsync(CancellationToken.None);
            using var stream = await result.ReadAsStreamAsync();
            using var reader = new StreamReader(stream);
            Assert.AreEqual("1", reader.ReadToEnd().Trim());

It will return an object which exposes an underlying stream, so any format can be used and parsed. Or, if you want to write it somewhere, CopyToAsync to another stream

[DarkWanderer]

Released version 2.0.0 with this