How to Use Window Functions in ParadeDB

How do I use window functions in ParadeDB?

Window functions let ParadeDB calculate running totals, rankings, and other analytics across related rows without collapsing them into groups.

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Description

Example H2

Example H3

What are ParadeDB window functions used for?

Window functions answer questions like running customer spend, order ranking, or stock percentage without losing row-level detail. They operate on a “window” of rows defined by PARTITION BY and ORDER BY clauses.

How is the basic syntax structured?

Write SELECT columns, add a function_name() OVER (PARTITION BY … ORDER BY …) AS alias, then reference the table. Each OVER clause sets the window frame.

Which built-in functions matter most?

ROW_NUMBER(), RANK(), DENSE_RANK(), SUM(), AVG(), LAG(), LEAD(), FIRST_VALUE(), LAST_VALUE(), and NTILE() cover most analytics needs.

How do I rank orders by total_amount?

SELECT id, customer_id, total_amount, RANK() OVER (PARTITION BY customer_id ORDER BY total_amount DESC) AS order_rank FROM Orders;

How to compute a customer’s running lifetime spend?

SELECT id, customer_id, order_date, total_amount, SUM(total_amount) OVER (PARTITION BY customer_id ORDER BY order_date) AS running_spend FROM Orders;

When should I use RANGE or ROWS?

ROWS counts physical rows; RANGE counts value ranges. Use ROWS for true running totals and RANGE for time-bucketed analytics.

Best practice: always set ORDER BY

Without ORDER BY PostgreSQL treats all rows in a partition as peers, making rankings unpredictable. Explicit ordering guarantees reproducible results.

Best practice: filter with WHERE, not HAVING

Window functions run after WHERE but before HAVING. Apply base filters in WHERE to avoid unnecessary computation.

Can I reuse the window definition?

Yes, OVER w AS (...) lets you name a window once and reuse it across many functions to keep queries readable and performant.

How do I combine aggregates and windows?

Select aggregate results in a subquery, then apply window functions in the outer query, or use FILTER() within the window to isolate rows.

Why How to Use Window Functions in ParadeDB is important

How to Use Window Functions in ParadeDB Example Usage


-- Top 3 most expensive products per order
SELECT
    oi.order_id,
    p.name,
    oi.quantity,
    (oi.quantity * p.price) AS line_total,
    RANK() OVER (
        PARTITION BY oi.order_id
        ORDER BY (oi.quantity * p.price) DESC
    ) AS price_rank
FROM   OrderItems AS oi
JOIN   Products    AS p ON p.id = oi.product_id
WHERE  oi.order_id = 42
ORDER  BY price_rank;

How to Use Window Functions in ParadeDB Syntax


SELECT
    column_list,
    window_function ( expression ) OVER (
        [PARTITION BY partition_expression, ...]
        [ORDER BY order_expression [ASC|DESC] NULLS {FIRST|LAST}, ...]
        [ROWS|RANGE BETWEEN frame_start AND frame_end]
    ) AS alias
FROM   table_name;

Example with ecommerce tables:

SELECT
    id,
    order_date,
    total_amount,
    SUM(total_amount) OVER (
        PARTITION BY customer_id
        ORDER BY order_date
        ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
    ) AS running_spend
FROM   Orders;

Common Mistakes

Using GROUP BY when a window function is needed. GROUP BY collapses rows and hides details; window functions keep every row visible. Remove GROUP BY and add OVER() to the aggregate.
Omitting ORDER BY in the OVER clause. Without ordering, rankings and running totals become nondeterministic. Always include ORDER BY for reproducible analytics.

Frequently Asked Questions (FAQs)

Can I filter on a window function result?

Yes. Wrap the query in a subquery or CTE, then filter on the alias in the outer SELECT.

Do window functions slow queries?

They can if partitions are large. Index the PARTITION BY and ORDER BY columns to help PostgreSQL sort efficiently.

Are window functions editable in ParadeDB views?

Yes. Create a view with the window logic; ParadeDB materializes it on-the-fly while remaining fully updatable if no aggregates change underlying keys.