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Data Structure
LiteDB store data as documents, which are JSON-like field and value pairs. Documents are a schemaless data structure. Each document has your data and structure together.
{
_id: 1,
name: { first: "John", last: "Doe" },
age: 37,
salary: 3456.0,
createdDate: { $date: "2014-10-30T00:00:00.00Z" },
phones: ["8000-0000", "9000-0000"]
}
-
_id
contains document primary key - an unique value in collection -
name
containts an embedded document withfirst
andlast
fields -
age
contains aInt32
value -
salary
contains aDouble
value -
createDate
contains aDateTime
value -
phones
contains an array ofString
LiteDB stores documents in collections. A collection is a group of related documents that have a set of shared common indexes. Collections are analogous to a table in relational databases.
LiteDB store documents in BSON data format (BSON are Binary JSON). BSON is a binary representation of JSON with additional type information. In the documents, the value of a field can be any of the BSON data types, including other documents, arrays, and arrays of documents. BSON is a fast and simple way to serialize documents in binary format.
LiteDB use a subset only of BSON data types. See all supported LiteDB BSON data types and .NET equivalent.
BSON Type | .NET type |
---|---|
MinValue | - |
Null | Any .NET object with null value |
Int32 | System.Int32 |
Int64 | System.Int64 |
Double | System.Double |
String | System.String |
Document | System.Collection.Generic.Dictionary<string, BsonValue> |
Array | System.Collection.Generic.List<BsonValue> |
Binary | System.Byte[] |
ObjectId | LiteDB.ObjectId |
Guid | System.Guid |
Boolean | System.Boolean |
DateTime | System.DateTime |
MaxValue | - |
To serialize a document to JSON, LiteDB use a extended version of JSON to not loose any BSON type information that not exists in JSON. Extended data type is represent as an embedded document, using inital $
key and value as string.
BSON data type | JSON representation | Description |
---|---|---|
ObjectId | { "$oid": "507f1f55bcf96cd799438110" } |
12 bytes in hex format |
Date | { "$date": "2015-01-01T00:00:00Z" } |
UTC and ISO-8601 format |
Guid | { "$guid": "ebe8f677-9f27-4303-8699-5081651beb11" } |
|
Binary | { "$binary": "VHlwZSgaFc3sdcGFzUpcmUuLi4=" } |
Byte array in base64 string format |
Int64 | { "$numberLong": "12200000" } |
|
MinValue | { "$minValue": "1" } |
|
MaxValue | { "$maxValue": "1" } |
LiteDB implements JSON in JsonSerializer
static class. Serialize and deserialize used only BsonValue
as input/output. If you want convert your object type, you need use BsonMapper
before.
var customer = new Customer { Id = 1, Name = "John Doe" };
var doc = BsonMapper.Global.ToDocument(customer);
var jsonString = JsonSerialize.Serialize(doc, pretty, includeBinaryData);
JsonSerialize
also supports TextReader
and TextWriter
to read/write direct from a file or Stream
.
ObjectId
is a 12 bytes BSON type:
-
Timestamp
: Value representing the seconds since the Unix epoch (4 bytes) -
Machine
: Machine identifier (3 bytes) -
Pid
: Process id (2 bytes) -
Increment
: A counter, starting with a random value (3 bytes)
In LiteDB, documents stored in a collection require a unique _id
field that acts as a primary key. Because ObjectIds
are small, most likely unique, and fast to generate, LiteDB uses ObjectIds
as the default value for the _id
field if the _id
field is not specified.
Unlike Guid data type, ObjectId are a sequencial number, so it's a better solution on indexing. ObjectId use hexa numbers to be represented in string
var id = ObjectId.NewObjectId();
// You can get creation datetime from an ObjectId
var date = id.CreationTime;
// ObjectId is represented in hex value
Debug.Print(id);
"507h096e210a18719ea877a2"
// Create a instance based on hex representation
var nid = new ObjectId("507h096e210a18719ea877a2");
Data Modeling
- Data Structure
- BsonDocument
- Object Mapping
- Relationships with Document References
- Collections
- FileStorage
Index
Query
Database
Version 4 changes
Shell