Query: Auto-buffer data readers in SqlServer when split query & MARS off

[smitpatel]

Resolves #21420

[roji]

Benchmark results:

BenchmarkDotNet=v0.12.0, OS=ubuntu 20.04
Intel Xeon W-2133 CPU 3.60GHz, 1 CPU, 12 logical and 6 physical cores
.NET Core SDK=5.0.100-preview.6.20318.15
  [Host]     : .NET Core 3.1.1 (CoreCLR 4.700.19.60701, CoreFX 4.700.19.60801), X64 RyuJIT
  DefaultJob : .NET Core 3.1.1 (CoreCLR 4.700.19.60701, CoreFX 4.700.19.60801), X64 RyuJIT

Method	Mean	Error	StdDev
WithoutConcurrentDictionary	6,411.03 ns	33.443 ns	31.283 ns
WithConcurrentDictionary	96.99 ns	0.212 ns	0.177 ns

i.e. avoid parsing connection strings if at all possible :)

Benchmark code

public class Program
{
    private static readonly ConcurrentDictionary<string, bool> _cache
        = new ConcurrentDictionary<string, bool>();

    private const string ConnectionString =
        "Server=localhost;Database=test;User=SA;Password=Abcd5678;ConnectRetryCount=0;MultipleActiveResultSets=true";

    [Benchmark]
    public bool WithoutConcurrentDictionary()
        => new SqlConnectionStringBuilder(ConnectionString).MultipleActiveResultSets;

    [Benchmark]
    public bool WithConcurrentDictionary()
        => _cache.GetOrAdd(ConnectionString,
            cs => new SqlConnectionStringBuilder(ConnectionString).MultipleActiveResultSets);

    static void Main(string[] args)
        => BenchmarkRunner.Run<Program>();
}

[ghost]

Hello @smitpatel!

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