pg_jsonschema

What it is

pg_jsonschema validates PostgreSQL json and jsonb values against JSON Schema. Validation can run in a query or become a check constraint that prevents invalid documents from being stored.

What it provides

• JSON and JSONB validation functions
• Validation of the schema document itself
• Validation diagnostics for malformed documents

Use it for flexible metadata columns, webhook payloads, configuration documents, user-defined forms, or event envelopes that need a database-enforced shape.

Use it with Rent

extension pg_jsonschema {
  name = "pg_jsonschema"
}

The RSL declaration makes installation and migration intent part of the reviewed application schema. Register the typed pack at runtime to call its APIs:

let jsonschema = extensions.register_pack::<PgJsonSchema>()?;
let valid_metadata = jsonschema.validates_jsonb(
    post::metadata(),
    serde_json::json!({"type": "object", "required": ["email"]}),
);

let posts = client
    .post()
    .where_raw(valid_metadata)
    .all()
    .await?;

let valid = jsonschema
    .client(&pool)
    .validate(schema, document)
    .await?;

Run the application

cargo run -p rent --example extension_12_pg_jsonschema

Set DATABASE_URL to a disposable PostgreSQL server with pg_jsonschema available and a role permitted to create databases and install it. The application stores post metadata with a reading_time field, validates positive and invalid values through the typed client, and filters rows with both JSON and JSONB predicates. It then adds a database CHECK constraint and proves that an invalid insert is rejected without changing the stored rows. The isolated database is removed afterward.

Query-time validation only filters a result; it does not protect future writes. Use a CHECK constraint when every writer must obey the schema. PostgreSQL still needs NOT NULL separately if SQL NULL is forbidden. Its standalone extension declaration is crates/rent/examples/extension_12_pg_jsonschema/schema.rsl.