MySQL 8.0: Unexpected Behavior with JSON Fields and Indexing in Compound Queries
I just started working with Can someone help me understand I'm relatively new to this, so bear with me... I'm relatively new to this, so bear with me. I am experiencing unexpected behavior when querying a MySQL 8.0 database that uses JSON fields in a compound index. I have a table `orders` defined as follows: ```sql CREATE TABLE orders ( id INT AUTO_INCREMENT PRIMARY KEY, customer_id INT, order_data JSON, INDEX idx_customer_order (customer_id, (order_data->>'$.status')) ); ``` The `order_data` JSON field contains structured data, including a `status` key. I expected that querying the table would leverage the compound index, but the performance is surprisingly slow, and it seems to be ignoring the index entirely. When I run the following query: ```sql SELECT * FROM orders WHERE customer_id = 1 AND order_data->>'$.status' = 'shipped'; ``` I noticed that it takes significantly longer than expected, and when I check the execution plan using `EXPLAIN`, it shows that the index is not being used, resulting in a full table scan. I tried to run the same query without the JSON condition, like this: ```sql SELECT * FROM orders WHERE customer_id = 1; ``` This returns results quickly, indicating that the index on `customer_id` is working. However, the addition of the condition on the JSON field seems to be causing issues. I’ve also verified that the `status` key exists in the JSON data for the relevant entries. To troubleshoot further, I’ve tried: - Rebuilding the index after inserting new data. - Using `CAST` to ensure data types are aligned. - Updating MySQL to the latest patch version (8.0.27). Despite trying these solutions, the performance issue persists, and the index still isn't being utilized. Has anyone faced a similar issue or can suggest how to make MySQL use the compound index with JSON fields effectively? Any insights would be greatly appreciated! This is part of a larger web app I'm building. I'm working on a web app that needs to handle this. Am I missing something obvious? Thanks in advance! Thanks for any help you can provide! Any help would be greatly appreciated!