Mateusz Kowalczyk

@mateuszkowalczyk

Database engineer working with PostgreSQL and MySQL in production. Posts cover SQL traps, indexes, locks, isolation levels and replication failures.

Member since Nov 5, 2026

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Banner: leading wildcard LIKE causing a full table scan versus a trigram index

Databases Bug Report

LIKE '%term%' was scanning 20 million rows on every search keystroke

Mateusz Kowalczyk · Nov 4, 2026 · 8 min read

The admin order search used LIKE with a leading wildcard. A B-tree index cannot help with that, so every search read the whole table, and the search-as-you-type box multiplied it. We compared a trigram index and full-text search on the same data and shipped both for different fields.