XDB is a database library that provides a tuple-based abstraction for modeling, storing, and querying data across multiple databases. Rather than writing database-specific schemas, queries, and migrations, XDB allows developers to model their domain once and use it with one or more databases.
Read about the motivation behind XDB in Introducing XDB.
A Tuple is the fundamental building block in XDB. It combines:
- Kind: Type of the record (similar to a table name)
- ID: Unique identifier within the kind
- Name: Attribute name (similar to a column)
- Value: The attribute's value
- Options: Key-value pairs for metadata
An Edge is a special kind of tuple that defines a unidirectional relationship between two records. Edges are used to model relationships in your domain model.
A Record is a collection of tuples that share the same kind and id. Records are similar to objects, structs, or rows in a database.
| Type | PostgreSQL | Description |
|---|---|---|
| String | TEXT | UTF-8 string |
| Integer | BIGINT | 64-bit signed integer |
| Float | DOUBLE PRECISION | 64-bit floating point number |
| Boolean | BOOLEAN | True or False |
| Timestamp | TIMESTAMPZ | Date and time in UTC |
| JSON | JSONB | JSON data type |
| Bytes | BYTEA | Binary data |
| Type | PostgreSQL | Description |
|---|---|---|
| Point | POINT | Latitude and Longitude |
| Money | JSONB | Currency and Amount |
| File | JSONB | File/Image metadata. Actual file is stored in a separate storage |
Drivers serve as the bridge between XDB's tuple-based model and specific database implementations. All drivers implement basic Reader and Writer capabilities, with advanced features like full-text search, aggregation, and iteration available based on the database's capabilities.
Stores provide higher-level APIs that combine multiple drivers to support common use-cases. Store implementations satisfy capability interfaces, allowing them to be used as drivers or layered together for complex scenarios.
The Schema APIs provide a database-agnostic way to define and manage your application's domain models. These APIs enable:
- Runtime type checking and constraint enforcement
- Generation of database-specific schemas
- Migration management