How to Create and Manage UDFs in ParadeDB in PostgreSQL

How do I create and use UDFs in ParadeDB on PostgreSQL?

The udfs command in ParadeDB lets you list, create, replace, and remove user-defined functions (UDFs) so they can be reused across SQL queries.

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Description

Example H2

Example H3

What does the udfs command do in ParadeDB?

The udfs helper surfaces every user-defined function registered in your ParadeDB-backed PostgreSQL database. You can quickly audit available logic, check argument lists, and view return types without scanning pg_catalog tables.

How do I list existing UDFs?

Run SELECT * FROM paradedb.udfs();. Each row shows schema, function_name, arg_types, return_type, and language. Filtering by schema keeps noisy extensions out of view:

SELECT * FROM paradedb.udfs() WHERE schema = 'public';

What is the syntax to create a new UDF?

The command is a wrapper around CREATE OR REPLACE FUNCTION. Use it when you need logic reused in multiple queries, e.g., computing customer lifetime value (CLV).

Parameters explained

function_name – unique identifier. arg_type – data type for each parameter. return_type – type of the value produced. LANGUAGE – e.g., SQL, plpgsql, plpython. VOLATILE, IMMUTABLE, or STABLE – planner hints. SECURITY DEFINER optionally elevates rights.

Example: Calculate Customer Lifetime Value

The function sums paid orders per customer.

CREATE OR REPLACE FUNCTION public.clv(p_customer_id INT) RETURNS NUMERIC AS $$ SELECT COALESCE(SUM(total_amount), 0) FROM Orders WHERE customer_id = p_customer_id; $$ LANGUAGE SQL IMMUTABLE; -- Query using the UDF SELECT c.id, c.name, clv(c.id) AS lifetime_value FROM Customers AS c ORDER BY lifetime_value DESC;

Because the UDF is IMMUTABLE, ParadeDB can cache results during vector search pipelines to speed up ranking.

When should I update or drop a UDF?

Use CREATE OR REPLACE FUNCTION to patch logic without breaking dependent views. Run DROP FUNCTION IF EXISTS schema.fn_name(arg_types); when the function is obsolete. Always include the argument list in the drop statement to avoid collisions.

Best practices for ParadeDB UDFs

Mark pure calculations as IMMUTABLE so ParadeDB’s query planner can inline them.
Keep business logic in SQL or plpgsql to simplify debugging; reserve procedural languages for heavy text or ML work.
Namespace functions inside dedicated schemas (e.g., analytics) to prevent name clashes.
Add comments via COMMENT ON FUNCTION so teammates understand usage.

Common mistakes and fixes

Forgetting argument types when dropping. Why it’s wrong: PostgreSQL treats each signature as unique. Fix: specify the full arg list.

Using VOLATILE for deterministic logic. Why it’s wrong: disables planner optimizations. Fix: mark as IMMUTABLE or STABLE.

Why How to Create and Manage UDFs in ParadeDB in PostgreSQL is important

How to Create and Manage UDFs in ParadeDB in PostgreSQL Example Usage


-- Show customers with low stock products in their last order using a UDF
CREATE OR REPLACE FUNCTION analytics.last_order_low_stock(p_customer_id INT)
RETURNS BOOLEAN AS $$
    WITH last_order AS (
        SELECT id
        FROM   Orders
        WHERE  customer_id = p_customer_id
        ORDER  BY order_date DESC
        LIMIT 1)
    SELECT EXISTS (
        SELECT 1
        FROM   OrderItems oi
        JOIN   Products   p ON p.id = oi.product_id
        WHERE  oi.order_id = (SELECT id FROM last_order)
          AND  p.stock < 5);
$$ LANGUAGE SQL STABLE;

SELECT c.id, c.name
FROM   Customers c
WHERE  last_order_low_stock(c.id);

How to Create and Manage UDFs in ParadeDB in PostgreSQL Syntax


CREATE [ OR REPLACE ] FUNCTION schema.function_name ( [ arg_name arg_type [, ...] ] )
RETURNS return_type
LANGUAGE { SQL | plpgsql | plpythonu | ... }
[ IMMUTABLE | STABLE | VOLATILE ]
[ SECURITY DEFINER | SECURITY INVOKER ]
AS $$
    -- function body
$$;

-- Example in ecommerce context
a) List all UDFs
   SELECT * FROM paradedb.udfs();

b) Create CLV function
   CREATE OR REPLACE FUNCTION public.clv(p_customer_id INT)
   RETURNS NUMERIC AS $$
       SELECT COALESCE(SUM(total_amount),0)
       FROM   Orders
       WHERE  customer_id = p_customer_id;
   $$ LANGUAGE SQL IMMUTABLE;

Common Mistakes

Dropping a UDF without its argument list leads to "function does not exist" errors. Always include arg types: DROP FUNCTION IF EXISTS public.clv(INT);
Labeling deterministic functions as VOLATILE prevents ParadeDB from caching results. Use IMMUTABLE for pure calculations to boost performance.