👀 Views: 13 💬 Answers: 1 📅 Created: 2025-06-27

mysql json performance SQL

I'm stuck on something that should probably be simple. I'm trying to implement I'm currently working with MySQL 8.0 and utilizing the JSON data type to store some semi-structured data. However, I'm running into performance optimization when trying to query this data, especially when using the `JSON_EXTRACT` function. I created a secondary index on the JSON field to improve performance, but it doesn't seem to be having the desired effect. Here’s what my table creation looks like: ```sql CREATE TABLE my_table ( id INT PRIMARY KEY, data JSON, INDEX idx_data ((CAST(data->>'$.field_name' AS CHAR(100)))) ); ``` I thought that creating a virtual column might help, so I tried this: ```sql ALTER TABLE my_table ADD COLUMN field_name VARCHAR(100) AS (data->>'$.field_name') STORED, ADD INDEX idx_field_name (field_name); ``` After adding the virtual column, I ran a query like: ```sql SELECT * FROM my_table WHERE field_name = 'SomeValue'; ``` Even with the index on the virtual column, the execution time is still quite slow. The query plan shows that it’s doing a full table scan instead of using the index. I’ve also tried running `ANALYZE TABLE my_table;` to refresh the statistics, but that didn’t seem to help. The size of my_table is around 1 million rows, and the `data` JSON column can store multiple fields with varying structures. Is there a specific configuration or indexing strategy that I might be missing to optimize performance for querying JSON fields? Any insights or recommendations would be greatly appreciated! Am I missing something obvious? For reference, this is a production mobile app.