PostgreSQL pipeline mode

BlueTusk.Client supports PostgreSQL pipeline mode on PostgreSQL 14 and later. A pipeline sends multiple extended-query synchronization groups in one network flush, preserves result order, and avoids waiting for each group before sending the next one.

This feature is independent of the .NET System.IO.Pipelines buffering library. BlueTusk implements PostgreSQL pipeline semantics over its existing synchronous and asynchronous transport. A separate benchmark-backed evaluation retained the ArrayPool/Span/Memory transport; see ADR 0005.

Each BlueTuskPipelineGroup ends with an explicit protocol Sync. A server error is attached to the affected group’s result after BlueTusk drains through that group’s ReadyForQuery. PostgreSQL can then execute the next already-sent group:

await using var session = await BlueTuskSession.OpenAsync(options);

var pipeline = await session.ExecutePipelineAsync(
[
    new BlueTuskPipelineGroup(
    [
        new BlueTuskBatchQuery("INSERT INTO app.items(value) VALUES (1)", []),
        new BlueTuskBatchQuery("INSERT INTO app.items(value) VALUES (2)", []),
    ]),
    new BlueTuskPipelineGroup(
    [
        new BlueTuskBatchQuery("SELECT count(*) FROM app.items", []),
    ]),
]);

foreach (var group in pipeline.Groups)
{
    if (group.Error is { } error)
    {
        Console.Error.WriteLine($"{error.SqlState}: {error.Message}");
    }
}

The synchronous ExecutePipeline method has the same ordered result and error contract. Query parameters use the same BlueTuskExtendedQueryParameter representation as other Client-layer extended-query APIs.

Cancellation sends PostgreSQL CancelRequest, drains the active group and every already-sent group to their synchronization boundaries, and throws OperationCanceledException only after the session is safe to reuse. A connection that fails during a partial write or cannot recover to ReadyForQuery is closed instead of being reused.

BlueTuskSession.Capabilities and BlueTuskConnection.ServerCapabilities expose the authenticated server version and detected features. ADO.NET physical sessions probe PostgreSQL 19’s documented information_schema.property_graphs view before enabling SupportsSqlPgq; low-level normal SQL sessions can call ProbeOptionalCapabilities or its asynchronous counterpart explicitly. SupportsOAuthBearer becomes true only on a connection that actually completed native OAUTHBEARER negotiation. A version number alone is not treated as product support.