When a LIKE '%value%' Slows Everything Down: A Real PostgreSQL Optimization Case

Tue, 06 Jan 2026 08:03:00 +0100

A few weeks ago, a client contacted me with a very common issue:

“Search in the admin console is slow. Sometimes it takes several seconds. We’ve already reduced the JOINs, but the problem hasn’t disappeared.”

Environment: PostgreSQL on managed cloud.
Main table: payment_report (~6 million rows, 3 GB).
Searched column: reference_code.

Problematic query:

SELECT *
FROM reporting.payment_report r
JOIN reporting.payment_cart c ON c.id = r.cart_id
WHERE c.service_id = 1001
 AND r.reference_code LIKE '%ABC123%'
ORDER BY c.created_at DESC
LIMIT 100;

🧠 First observation: the JOINs were not the problem #

I compared:

Indexes on Ivan Luminaria

When a LIKE '%value%' Slows Everything Down: A Real PostgreSQL Optimization Case

🧠 First observation: the JOINs were not the problem #