Storage & Nested Objects

Atscript fields can be stored in the database in three different ways. Understanding these storage modes is key to designing queryable, efficient schemas.

Three Storage Modes

Mode	Applies To	What Happens	Queryable?
Column	Scalar fields (string, number, boolean, decimal)	One field → one database column	Yes
Flattened	Nested objects (default)	Each nested field → a __-separated column	Yes
JSON	@db.json objects, all arrays	Entire value → single JSON column	Adapter-dependent

Column Storage

Scalar fields map directly to database columns — one field, one column. This is the default behavior for all scalar types and requires no annotation:

@db.table 'users'
export interface User {
    @meta.id
    id: number

    name: string       // → column: name
    email: string      // → column: email
    active: boolean    // → column: active
}

Flattened Storage

By default, nested objects are flattened into separate columns using __ (double underscore) as a separator:

@db.table 'profiles'
export interface Profile {
    @meta.id
    id: number

    name: string

    contact: {
        email: string
        phone?: string
    }
}

This creates four columns: id, name, contact__email, and contact__phone. When you read data back, the flat columns are automatically reconstructed into the nested object structure.

Deep Nesting

Flattening works recursively at any depth:

settings: {
    notifications: {
        email: boolean
        sms: boolean
    }
}
// Columns: settings__notifications__email, settings__notifications__sms

Querying Flattened Fields

Flattened fields are real database columns — you can filter and sort on them using dot notation. The path is translated to the physical column name automatically:

const results = await profiles.findMany({
  filter: { 'contact.email': 'alice@example.com' },
})
// Translates to: WHERE contact__email = 'alice@example.com'

TIP

Flattened fields give you the best of both worlds: you work with nested objects in your code, but each field is a real, indexed, queryable column in the database.

JSON Storage

Use @db.json to store a nested object as a single JSON column instead of flattening it:

@db.json
preferences: {
    theme: string
    lang: string
    shortcuts: string[]
}
// Single column: preferences (stored as JSON string in SQLite, JSONB in PostgreSQL, native object in MongoDB)

When to use @db.json:

• Complex objects you don't need to query by individual sub-fields
• Dynamic or loosely-structured data where flattening creates too many columns
• Highly nested structures where deep flattening is impractical

TIP

Arrays are always stored as JSON regardless of @db.json. You only need the annotation for plain objects you want to keep as a single column.

Queryability

The storage mode determines what you can query:

Flattened fields are fully queryable — they are real columns with their own types, indexes, and constraints. You can filter, sort, and index them like any other field.

JSON fields have limited and adapter-dependent queryability:

Adapter	JSON Query Support
SQLite	Limited — json_extract() via raw queries
PostgreSQL	JSONB operators and indexing
MySQL	JSON functions
MongoDB	Native nested query syntax (objects are stored natively)

See Adapters for adapter-specific details on JSON querying.

INFO

If you need to filter on a field, prefer flattened storage (the default for objects). Use @db.json only when you treat the object as an opaque blob that is read and written as a whole.

Example: Same Schema, Different Storage

Consider a Product type with two nested objects — one flattened, one stored as JSON:

@db.table 'products'
export interface Product {
    @meta.id
    id: number

    name: string

    // Flattened (default) — each field becomes a column
    dimensions: {
        width: number
        height: number
        weight: number
    }

    // JSON — stored as a single column
    @db.json
    metadata: {
        tags: string[]
        attributes: { key: string, value: string }[]
    }
}

This produces the following database columns:

Column	Source	Storage Mode
id	id	Column
name	name	Column
dimensions__width	dimensions.width	Flattened
dimensions__height	dimensions.height	Flattened
dimensions__weight	dimensions.weight	Flattened
metadata	metadata	JSON

You can filter on dimensions.width (it's a real column), but querying inside metadata requires adapter-specific JSON functions.

Next Steps

• Defaults & Generated Values — auto-generated values and static defaults
• Indexes & Constraints — database indexes, precision, and collation
• Tables & Fields — declaring tables, primary keys, and field types