👀 Views: 18 💬 Answers: 1 📅 Created: 2025-06-12

mysql json indexing performance SQL

I'm refactoring my project and I've searched everywhere and can't find a clear answer... I'm currently facing a performance issue when trying to query a table with a JSON field in MySQL 8.0. The table `users` contains a JSON column `settings` that stores various user preferences, and I have created a functional index on this JSON field to optimize queries. However, even with the index, I'm experiencing significant slowdowns when using the `JSON_EXTRACT` function within my `WHERE` clause. Here’s the query I'm running: ```sql SELECT * FROM users WHERE JSON_EXTRACT(settings, '$.notifications.email') = 'true'; ``` Initially, I thought the functional index would enhance performance, so I created it like this: ```sql CREATE INDEX idx_email_notifications ON users ((JSON_EXTRACT(settings, '$.notifications.email'))); ``` However, when I execute the query, I notice that the execution plan indicates a full table scan instead of using the index. I checked using `EXPLAIN` and got the following output: ``` +----+-------------+-------+-------+---------------+---------+---------+----------------+------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+-------+---------------+---------+---------+----------------+------+-------------+ | 1 | SIMPLE | users | ALL | NULL | NULL | NULL | NULL | 1000 | Using where | +----+-------------+-------+-------+---------------+---------+---------+----------------+------+-------------+ ``` I've tried updating statistics on the table and even dropping and recreating the index, but the performance hasn’t improved. Is there a known issue with JSON indexing in MySQL 8.0 that could lead to this behavior? Or perhaps I'm missing an optimization technique when working with JSON fields? Any insights or suggestions would be greatly appreciated. I'm working on a CLI tool that needs to handle this. I'm open to any suggestions. I've been using Sql for about a year now. Cheers for any assistance!