MLE: Running JavaScript Inside Oracle Database

Oracle 23ai ships MLE (Multi-Language Engine) as a fully supported feature. MLE allows you to write stored procedures, functions, and triggers in JavaScript (using the GraalVM runtime) and run them inside the Oracle Database process.

Creating a JavaScript function:

CREATE OR REPLACE MLE MODULE formatting_utils
LANGUAGE JAVASCRIPT AS
$$
export function formatCurrency(amount, currency = 'USD') {
    return new Intl.NumberFormat('en-US', {
        style: 'currency',
        currency: currency
    }).format(amount);
}

export function slugify(text) {
    return text.toLowerCase()
               .replace(/[^a-z0-9]+/g, '-')
               .replace(/^-|-$/g, '');
}
$$;

Calling JavaScript from SQL:

CREATE OR REPLACE FUNCTION format_currency(p_amount NUMBER, p_currency VARCHAR2 DEFAULT 'USD')
RETURN VARCHAR2
AS MLE MODULE formatting_utils SIGNATURE 'formatCurrency(number, string)';
/

SELECT product_name,
       format_currency(price) AS formatted_price
FROM   products;

Accessing the database from JavaScript:

-- JavaScript can issue SQL within the same session
CREATE OR REPLACE MLE MODULE order_processor
LANGUAGE JAVASCRIPT AS
$$
export function processOrder(orderId) {
    const result = session.execute(
        'SELECT status FROM orders WHERE order_id = :id',
        { id: orderId }
    );
    if (result.rows[0].STATUS === 'PENDING') {
        session.execute(
            'UPDATE orders SET status = :s WHERE order_id = :id',
            { s: 'PROCESSING', id: orderId }
        );
    }
}
$$;

Why this matters: Teams with JavaScript expertise can now contribute to database-layer logic without learning PL/SQL. Complex string manipulation, JSON processing, and business rules that are awkward in PL/SQL are natural in JavaScript.

The runtime is GraalVM — a secure, sandboxed JavaScript engine. It does not have access to the filesystem or network outside of Oracle’s SQL interface.

Author: matheusdba