BTDB 33.6.8

BTDB

Currently this project these parts:

• Key Value Database
• Wrapped Dynamic IL generation with debugging + extensions
• IOC Container (SourceGenerator based)
• Object Database with Relations
• Snappy Compression
• Event Storage
• Bon (Binary object notation)
• Incremental SourceGenerator for IOC Container factory generation

All code written in C# 12 and licensed under very permissive MIT license. Targeting .Net 9.0, main code has just 2 dependencies (Microsoft.Extensions.Primitives, Microsoft.Extensions.ObjectPool). Code is tested using xUnit Framework. Used in production on Windows and Linux, on MacOS works as well. Please is you find it useful or have questions, write me e-mail boris.letocha@gmail.com so I know that it is used. It is available in Nuget http://www.nuget.org/packages/BTDB. Source code drops are Github releases.

Breaking changes

33.0.0

KeyValueDB

Nearly all IKeyValueDBTransaction methods moved into IKeyValueDBCursor. IKeyValueDBTransaction has method CreateCursor() to create IKeyValueDBCursor. Created cursor must not be used after transaction Commit. And all cursors must be disposed before transaction is disposed. It makes implementation of custom transaction wrappers more difficult, look at KeyValueDBTransactionWithCount for example.

ObjectDB

Positive breaking change is that DB could be modified in parallel to enumeration. It is possible due to KeyValueDB has now Cursors which correctly update their position even when DB is modified. It is even possible to delete current object in enumeration and enumeration will still continue correctly. Relations cannot return IEnumerator<T> anymore, it must be replaced by IEnumerable<T>. Also IOrderedDictionaryEnumerator is now inherited from IDisposable and must be disposed. Forgetting dispose will cause exception during transaction disposal.

Key Value Database

Features

• This is Key Value store written in C# with implementation on native heap (has also prefix compression). InMemory version uses managed heap.
• It is easily embeddable.
• One storage is just one directory.
• It has ACID properties with MVCC.
• At one time there could be multiple read only transactions and one read/write transaction.
• Export/Import to stream - could be used for compaction, snapshotting
• Automatic compaction
• Customizable compression (key index file could be Brotli compressed)
• Relatively Fast DB Open due to key index file - though it still needs to load all keys to memory
• Inspired by Bitcask [https://github.com/basho/bitcask/blob/develop/doc/bitcask-intro.pdf]

Design limits

• All keys data needs to fit in RAM
• Maximum Key length is limited by 31bits (2GB).
• Maximum value length is limited by 31bits (2GB).

Sample code

using (var fileCollection = new InMemoryFileCollection())
using (IKeyValueDB db = new KeyValueDB(fileCollection))
{
    using (var tr = db.StartTransaction())
    {
        tr.CreateOrUpdateKeyValue(new byte[] { 1 }, new byte[100000]);
        tr.Commit();
    }
}

Roadmap

• Everything is there just use it

Wrapped Dynamic IL generation with debugging + extensions

This help you to write fluent code which generates IL code in runtime. It is used in Object Database part.

Sample code

var method = ILBuilder.Instance.NewMethod<Func<Nested>>("SampleCall");
var il = method.Generator;
var local = il.DeclareLocal(typeof(Nested), "n");
il
    .Newobj(() => new Nested())
    .Dup()
    .Stloc(local)
    .Ldstr("Test")
    .Call(() => ((Nested)null).Fun(""))
    .Ldloc(local)
    .Ret();
var action = method.Create();

Roadmap

• Add support for all IL instructions as needed
• Deprecate this by replacing its usages by Source Generator

Object Database

Features

• Builds on top of Key Value Database and Reflection.Emit extensions.
• It stores Plain .Net Objects and only their public properties with getters and setters.
• All ACID and MVCC properties are preserved of course.
• Automatic upgrading of model on read with dynamically generated optimal IL code.
• Automatic versioning of model changes.
• Enumeration of all objects
• Each object type could store its "singleton" - very useful for root objects
• Relations - Table with primary key and multiple secondary keys
• By default objects are stored inline in parent object, use IIndirect for objects with Oid which will load lazily

Documentation: [https://github.com/Bobris/BTDB/blob/master/Doc/ODBDictionary.md]

Relations doc: [https://github.com/Bobris/BTDB/blob/master/Doc/Relations.md]

Sample code

public class Person
{
    public string Name { get; set; }
    public uint Age { get; set; }
}

using (var tr = _db.StartTransaction())
{
    tr.Store(new Person { Name = "Bobris", Age = 35 });
    tr.Commit();
}
using (var tr = _db.StartTransaction())
{
    var p = tr.Enumerate<Person>().First();
    Assert.AreEqual("Bobris", p.Name);
    Assert.AreEqual(35, p.Age);
}

Roadmap

• Support more types of properties
• Free text search (far future if ever)

Event storage

Features

• Optimal serialization with metadata
• Deserialization also to dynamic
• Storage is transactional
• As storage could be used Azure Page Blobs
• EventStorage2 is specialized to be used with Kafka, metadata are stored in separate topic

Bon

Bon Binary object notation is allows creating and reading JavaScript/C# values with extensions like Dictionary/Map into binary notation. It is much faster to parse, write, skip, search by keys than JSON, size will be also smaller in most cases, in some cases much more smaller.

Snappy Compression

Features

• Ported and inspired mainly by Go version of Snappy Compression [http://code.google.com/p/snappy/]
• Fully compatible with original
• Fully managed and safe implementation
• Compression is aborted when target buffer size is not big enough

Roadmap

• Some speed optimizations around Spans would help