Fields & Types

Define your model fields with various scalar types, modifiers, and attributes for complete control over your database schema.

Scalar Types

Prax provides scalar types that map to native database types and Rust types:

Prax Type	Rust Type	PostgreSQL	MySQL	SQLite
`Int`	i32	INTEGER	INT	INTEGER
`BigInt`	i64	BIGINT	BIGINT	INTEGER
`Float`	f64	DOUBLE PRECISION	DOUBLE	REAL
`Decimal`	rust_decimal::Decimal	DECIMAL	DECIMAL	REAL
`String`	String	TEXT	VARCHAR(191)	TEXT
`Boolean`	bool	BOOLEAN	TINYINT(1)	INTEGER
`DateTime`	chrono::DateTime<Utc>	TIMESTAMP(3)	DATETIME(3)	TEXT
`Json`	serde_json::Value	JSONB	JSON	TEXT
`Bytes`	Vec<u8>	BYTEA	LONGBLOB	BLOB

Type Modifiers

Modifiers change how field values are handled:

Modifier	Syntax	Rust Type	Description
Required	`String`	String	Must have a value (NOT NULL)
Optional	`String?`	Option<String>	Can be NULL
Array	`String[]`	Vec<String>	List of values
Optional Array	`String[]?`	Option<Vec<String>>	Array that can be NULL

Field Attributes

Attributes modify field behavior and add constraints:

Primary Keys

Every model needs a unique identifier. Choose the right primary key strategy for your use case:

Auto-Increment

Best for simple applications with a single database. Compact and fast.

UUID/CUID/ULID

Best for distributed systems, APIs, or when you need to generate IDs client-side.

Default Values

Set default values to simplify record creation and ensure data consistency:

Timestamps

Track when records are created, updated, and deleted:

JSON Fields

Store flexible, schema-less data in JSON fields:

Note: JSON fields are flexible but lack schema enforcement. Document the expected structure in comments and consider validation in your application layer.

Array Fields

Store multiple values in a single field (PostgreSQL native support, emulated on other databases):

Decimal Fields

Use Decimal for exact precision, especially for financial data:

Binary Data

Store binary data like files, images, or hashes:

Database-Specific Types

Use @db.TypeName to specify native database types for advanced use cases:

Field Attributes Reference

Attribute	Description
`@id`	Marks field as primary key
`@auto`	Auto-increment (for Int primary keys)
`@unique`	Unique constraint on field
`@default(value)`	Default value (literal, function, or dbgenerated)
`@updatedAt`	Auto-update timestamp on record changes
`@map("name")`	Custom column name in database
`@db.Type`	Specific database column type
`@ignore`	Exclude from generated client
`@relation(...)`	Define relationship to another model