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()
    .filter_raw(valid_metadata)
    .all()
    .await?;

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

Add the extension declaration above to your application's schema. Confirm that your PostgreSQL provider offers the extension and that your migration role can install it, then apply the migration and run your application:

rent migrate dev --name enable_pg_jsonschema
cargo run

Use a database CHECK constraint when every writer must obey the JSON schema. Query-time validation only filters that query. Add NOT NULL separately if SQL NULL is forbidden.

Complete example

Download this project, or copy the files below into an empty directory.

Replace RENT_REPOSITORY_URL in Cargo.toml with the URL supplied with your preview access. Use the matching Rent CLI release.

Use an empty PostgreSQL database with the extension binaries available on its server. Set DATABASE_URL to that database and follow any server setup requirements described above.

rent extension check --provider self-hosted
rent generate
rent migrate dev --name initial
cargo run

If your host preinstalls other extensions, declare those in RSL as well. For a database with existing application tables, baseline it first.

Cargo.toml

[package]
name = "rent-extension-pg-jsonschema"
version = "0.1.0"
edition = "2024"
[workspace]
[[bin]]
name = "rent-extension-pg-jsonschema"
path = "main.rs"
[dependencies]
rent = { git = "RENT_REPOSITORY_URL", tag = "v0.8.6", default-features = false, features = ["postgres", "extensions", "migrate"] }
rent-ext-pg-jsonschema = { git = "RENT_REPOSITORY_URL", tag = "v0.8.6" }
anyhow = "1.0.104"
tokio = { version = "1.53.1", features = ["full"] }
serde_json = "1.0.151"

rent.toml

schema = "schema.rsl"
generated = "generated"
migrations = "migrations"

[database]
dialect = "postgres"
backends = ["postgres"]

schema.rsl

datasource db {
  provider = "postgresql"
}

extension pg_jsonschema {
  name = "pg_jsonschema"
}

model Post {
  id    BigInt  @id
  title String
  body  String  @default("")
}

main.rs

use anyhow::Result;
use rent::{driver::DatabasePool, extension::ExtensionRegistry};
#[allow(dead_code, unused_imports)]
#[rustfmt::skip]
#[path = "generated/mod.rs"]
mod generated;
#[tokio::main]
async fn main() -> Result<()> {
    let pool = DatabasePool::connect_url(&std::env::var("DATABASE_URL")?).await?;
    let mut extensions = ExtensionRegistry::default();
    use rent_ext_pg_jsonschema::{PgJsonSchema, PgJsonSchemaClientExt};
    let pack = extensions.register_pack::<PgJsonSchema>()?;
    let schema = serde_json::json!({"type":"object", "required":["email"]});
    let value = serde_json::json!({"email":"maya@example.com"});
    anyhow::ensure!(pack.client(&pool).validate(schema, value).await?);
    println!("The metadata satisfies its schema.");
    Ok(())
}

pg_jsonschema

What it is

What it provides

Use it with Rent

Run the application

Complete example

On this page