Note
This project was formerly known as VKV and has been renamed to DryDB.
DryDB is a read-only embedded B+Tree based key/value database, implemented pure C#.
| Method | Mean | Error | StdDev |
|------------------- |------------:|----------:|----------:|
| DryDB_FindByKey | 37.57 us | 0.230 us | 0.120 us |
| CsSqlite_FindByKey | 4,322.48 us | 44.492 us | 26.476 us |
- B+Tree based query
- Read a value by primary key
- Read values by key range
- Read values by key prefix
- Count by key range
- Secondary index
- unique
- non-unique
- Multiple Tables
- Support for both async and sync
- Sort by asc/desc
- C# Serialization
- MessagePack
- (Other formats are under planning.
- Unity Integration
AsyncReadManager+NativeArray<byte>based optimized custom loader.
- Custom key encoding
- Simple ascii/u8 byte sequence string (default)
- Int64
- UUIDv7 (only for .NET 9 or later. Needs
Guid.CreateVersion7()) - Ulid
- Page filter
- Built-in filters
- Cysharp/NativeCompression based page compression.
- We can write custom filters in C#.
- Built-in filters
- Iterator API
- By manipulating the cursor, large areas can be accessed sequentially.
- CLI tool
- Support for large BLOBs. (Values exceeding 65,536 bytes are stored on a separated page.)
| Package | Description | Latest version |
|---|---|---|
| DryDB | Main package. Embedded key/value store implementation. |  |
| DryDB.MessagePack | Plugin that handles value as MessagePack-Csharp. |  |
| DryDB.Compression | Plugin for compressing binary data. |  |
| DryDB.UlidKey | Plugin enabling the use of ulid as a key |  |
Note
Requirements: Unity 2022.2 or later.
- Install NuGetForUnity.
- Install the DryDB package and the optional plugins listed above using NuGetForUnity.
- Open the Package Manager window by selecting Window > Package Manager, then click on [+] > Add package from git URL and enter the following URL:
-
https://github.com/hadashiA/DryDB.git?path=src/DryDB.Unity/Assets/DryDB#1.0.2
-
We distribute the CLI tool as a dotnet tool.
$ dotnet tool install drydb.cliSee CLI tool section for the usage.
// Create DB
var builder = new DatabaseBuilder
{
// The smallest unit of data loaded into memory
PageSize = 4096,
};
// Create table (string key - ascii comparer)
var table1 = builder.CreateTable("items", KeyEncoding.Ascii);
table1.Append("key1", "value1"u8.ToArray()); // value is any `Memory<byte>`
table1.Append("key2", "value2"u8.ToArray());
table1.Append("key3", "value3"u8.ToArray());
table1.Append("key4", "value4"u8.ToArray());
// Create table (Int64 key)
var table2 = builder.CreateTable("quests", KeyEncoding.Int64LittleEndian);
table2.Append(1, "hoge"u8.ToArray());
// Build
await builder.BuildToFileAsync("/path/to/bin.drydb");// Open DB
var database = await ReadOnlyDatabase.OpenAsync("/pth/to/bin.drydb", new DatabaseLoadOptions
{
// Maximum number of pages to keep in memory
// Basically, page cache x capacity serves as a rough estimate of memory usage.
PageCacheCapacity = 32,
});
var table = database.GetTable("items");
// find by key (string key)
using var result = table.Get("key1");
result.IsExists //=> true
result.Span //=> "value1"u8
// byte sequence key (fatest)
using var result = table.Get("key1"u8);
// find key range. ("key1" between "key3")
using var range = table.GetRange(
startKey: "key1"u8,
endKey: "key3"u8,
startKeyExclusive: false,
endKeyExclusive: false,
sortOrder: SortOrder.Ascending);
range.Count //=> 3
// "key1" <=
using var range = table.GetRange("key1"u8, KeyRange.Unbound);
// "key1" <
using var range = table.GetRange("key1"u8, KeyRange.Unbound, startKeyExclusive: true);
// "key999" >=
using var range = table.GetRange(KeyRange.UnBound, "key999");
// "key999" >
using var range = table.GetRange(KeyRange.UnBound, "key999", endKeyExclusive: true);
// count
var count = table.CountRange("key1", "key3");
// async
using var value1 = await table.GetAsync("key1");
using var range1 = await table.GetRangeAsync("key1", "key3");
var count = await table.CountRangeAsync();var table1 = builder.CreateTable("items", KeyEncoding.Ascii);
table1.Append("key1", "value1"u8.ToArray()); // value is any `Memory<byte>`
table1.Append("key2", "value2"u8.ToArray());
table1.Append("key3", "value3"u8.ToArray());
table1.Append("key4", "value4"u8.ToArray());
// Buiild secondary index (non-unique)
table1.AddSecondaryIndex("category", isUnique: false, KeyEncoding.Ascii, (key, value) =>
{
// This lambda expression defines a factory that generates an index from any value.
if (key.Span.SequenceEqual("key1") ||
key.Span.SequenceEqual("key3"))
{
return "category1";
}
else
{
return "category2";
}
});
// Build
await builder.BuildToFileAsync("/path/to/bin.drydb");var table = database.GetTable("items");
// get "category1" values
table.Index("category").GetAll("category1"u8); //=> "value1", "value3"
// get range
table.Index("category").GetRange("category1"u8, "category2"u8);
// async
await table.Index("category").GetAllAsync("category1"u8.ToArray());
await table.Index("category").GetRangeAsync(...);Fetching all values beforehand consumes a lot of memory.
If you want to process each row sequentially in a table, you can further suppress memory consumption by using RangeIterator.
using var iterator = table.CreateIterator();
// Get current value..
iterator.CurrentKey //=> "key01"u8
iterator.CurrentValue //=> "value01"u8
// Seach and seek to the specified key position
iterator.TrySeek("key03"u8);
iterator.CurrentKey //=> "key03"u8;
iterator.CurrentValue //=> "value03"u8;
// Seek with async
await iterator.TrySeekAsync("key03");RangeIterator also provides the IEnumerable and IAnycEnumerable interfaces.
iterator.Current //=> "value03"u8
iterator.MoveNext();
iterator.Current //=> "value04"u8
// async
await iterator.MoveNextASync();
iterator.Current //=> "value05"u8We can also use foreach and await foreach with iterators.
It loops from the current seek position to the end.
We can store arbitrary byte sequences in value, but it would be convenient if you could store arbitrary C# types.
DryDB currently provides built-in serialization by the following libraries:
- MessagePack-CSharp
- System.Text.Json (in progress)
Installing the DryDB.MessagePack package enables the following features:
[MessagePackObject]
public class Person
{
[Key(0)]
public string Name { get; set; } = "";
[Key(1)]
public int Age { get; set; }
}// Create MessagePack value table...
using DryDB;
using DryDB.MessagePack;
var databaseBuilder = new DatabaseBuilder();
var tableBuilder = builder.CreateTable("items", KeyEncoding.Ascii)
.AsMessagePackSerializable<Person>();
// Add MessagePack serialized values...
var tableBuilder.Append("key01", new Person { Name = "Bob", Age = 22 });
var tableBuilder.Append("key02", new Person { Name = "Tom", Age = 34 });
// Secondary index example
tableBuilder.AddSecondaryIndex("age", false, KeyEncoding.Int64LittleEndian, (key, person) =>
{
return person.Age;
});
await builder.BuildToFileAsync("/path/to/db.drydb");// Load from messagepack values
using DryDB;
using DryDB.MessagePack;
using var database = await ReadOnlyDatabase.OpenAync("/path/to/db.drydb");
var table = database.GetTable("items")
.AsMessagePackSerializable<Person>();
Person value = tabel.Get("key01"); //=> Person("Bob", 22)// The page cache will use the unity native allocator.
var database = await ReadOnlyDatabase.OpenFromFileAsync(filePath, new DatabaseLoadOptions
{
StorageFactory = UnityNativeAllocatorFileStorage.Factory,
});$ dotnet tool install drydb.cli --prereleaseAfter install, specify the DB file and start an interactive session.
$ dotnet drydb --file ./sample.drydb
During an interactive session, the following commands are available.
| Command | Description |
|---|---|
| get | Get value by key |
| scan [offset] [limit] | Scan key-value entries (default: offset=0, limit=20) |
| keys [offset] [limit] | Scan keys only |
| values [offset] [limit] | Scan values only |
| prefix <key> [limit] | Search by key prefix (default: limit=10) |
| count | Count all entries |
| tables | List all tables |
| use [table] | Switch to another table |
| info | Show database info |
| help | Show this help |
| quit | Exit the session |
┌─────────────────────────────────────────────────────────────────────────────┐
│ .drydb File Format │
├─────────────────────────────────────────────────────────────────────────────┤
│ │
│ ┌───────────────────────────────────────────────────────────────────────┐ │
│ │ Header (14 bytes) │ │
│ ├───────────┬───────────┬───────────┬───────────────┬───────────────────┤ │
│ │ MagicBytes│ Version │FilterCount│ PageSize │ TableCount │ │
│ │ "DRY\0" │Major|Minor│ ushort │ int │ ushort │ │
│ │ 4 bytes │ 1b | 1b │ 2 bytes │ 4 bytes │ 2 bytes │ │
│ └───────────┴───────────┴───────────┴───────────────┴───────────────────┘ │
│ │ │
│ ▼ │
│ ┌───────────────────────────────────────────────────────────────────────┐ │
│ │ PageFilter[FilterCount] │ │
│ ├───────────────────────────────────────────────────────────────────────┤ │
│ │ ┌─────────────┬─────────────────────────┐ │ │
│ │ │ NameLength │ Name (UTF-8) │ × FilterCount │ │
│ │ │ 1 byte │ variable bytes │ │ │
│ │ └─────────────┴─────────────────────────┘ │ │
│ └───────────────────────────────────────────────────────────────────────┘ │
│ │ │
│ ▼ │
│ ┌───────────────────────────────────────────────────────────────────────┐ │
│ │ Table[TableCount] │ │
│ ├───────────────────────────────────────────────────────────────────────┤ │
│ │ ┌─────────────┬─────────────────┬─────────────────┬────────────────┐ │ │
│ │ │ NameLength │ Name (UTF-8) │ PrimaryIndex │ SecondaryIndex │ │ │
│ │ │ 4 bytes │ variable bytes │ Descriptor │ Descriptors │ │ │
│ │ └─────────────┴─────────────────┴─────────────────┴────────────────┘ │ │
│ └───────────────────────────────────────────────────────────────────────┘ │
│ │ │
│ ▼ │
│ ┌───────────────────────────────────────────────────────────────────────┐ │
│ │ B+Tree Pages │ │
│ └───────────────────────────────────────────────────────────────────────┘ │
│ │
└─────────────────────────────────────────────────────────────────────────────┘
┌─────────────────────────────────────────────────────────────────────────────┐
│ Index Descriptor │
├────────────┬─────────────┬──────────┬────────────┬──────────┬──────────┬────────────┤
│ NameLength │ EncodingLen │ Name │ EncodingId │ IsUnique │ ValueKnd │ RootPosion │
│ ushort │ ushort │ UTF-8 │ UTF-8 │ bool │ enum │ long │
│ 2 bytes │ 2 bytes │ variable │ variable │ 1 byte │ 1 byte │ 8 bytes │
└────────────┴─────────────┴──────────┴────────────┴──────────┴──────────┴────────────┘
┌─────────────────────────────────────────────────────────────────────────────┐
│ Page Structure │
├─────────────────────────────────────────────────────────────────────────────┤
│ │
│ ┌─────────────────────────────────────────────────────────────────────┐ │
│ │ Page Header (28 bytes) │ │
│ ├───────────┬───────────┬────────────┬──────────────┬────────────────┤ │
│ │ PageSize │ Kind │ EntryCount │ LeftSibling │ RightSibling │ │
│ │ int │ enum │ int │ long │ long │ │
│ │ 4 bytes │ 4 bytes │ 4 bytes │ 8 bytes │ 8 bytes │ │
│ └───────────┴───────────┴────────────┴──────────────┴────────────────┘ │
│ │ │
│ Kind = 0 (Leaf) │ Kind = 1 (Internal) │
│ │ │ │ │
│ ▼ │ ▼ │
│ ┌───────────────────────┐ │ ┌───────────────────────┐ │
│ │ EntryMeta[EntryCount] │ │ │ EntryMeta[EntryCount] │ │
│ ├───────────────────────┤ │ ├───────────────────────┤ │
│ │ PageOffset │ 4 bytes │ │ │ PageOffset │ 4 bytes │ │
│ │ KeyLength │ 2 bytes │ │ │ KeyLength │ 2 bytes │ │
│ │ ValueLength│ 2 bytes │ │ └───────────────────────┘ │
│ └───────────────────────┘ │ │ │
│ │ │ ▼ │
│ ▼ │ ┌───────────────────────┐ │
│ ┌───────────────────────┐ │ │ Entry[EntryCount] │ │
│ │ Entry[EntryCount] │ │ ├───────────────────────┤ │
│ ├───────────────────────┤ │ │ Key │ variable │ │
│ │ Key │ variable │ │ │ ChildPtr │ 8 bytes │ │
│ │ Value │ variable │ │ └───────────────────────┘ │
│ └───────────────────────┘ │ │
│ │ │
└─────────────────────────────────────────────────────────────────────────────┘
┌─────────────────────────────────────────────────────────────────────────────┐
│ B+Tree Structure │
├─────────────────────────────────────────────────────────────────────────────┤
│ │
│ ┌─────────────┐ │
│ │ Internal │ │
│ │ (Root) │ │
│ └──────┬──────┘ │
│ ┌────────────┼────────────┐ │
│ ▼ ▼ ▼ │
│ ┌──────────┐ ┌──────────┐ ┌──────────┐ │
│ │ Internal │ │ Internal │ │ Internal │ │
│ └────┬─────┘ └────┬─────┘ └────┬─────┘ │
│ │ │ │ │
│ ┌────────┴────────┐ │ ┌────────┴────────┐ │
│ ▼ ▼ ▼ ▼ ▼ │
│ ┌────────┐ ┌────────┬────────┐ ┌────────┐ │
│ │ Leaf │◄──────►│ Leaf │ Leaf │◄─────►│ Leaf │ │
│ │ k1:v1 │ │ k2:v2 │ k3:v3 │ │ k4:v4 │ │
│ │ ... │ │ ... │ ... │ │ ... │ │
│ └────────┘ └────────┴────────┘ └────────┘ │
│ ▲ ▲ │
│ │ Left/Right Sibling Links │ │
│ └────────────────────────────────────────────┘ │
│ │
└─────────────────────────────────────────────────────────────────────────────┘
MIT