MySQL 8.0: Performance Issues with Mixed Data Types in Composite Indexes
I'm not sure how to approach Quick question that's been bugging me - I'm experiencing significant performance degradation when querying a table with a composite index that includes both integer and string columns... The table in question has around 1 million rows, and the composite index is defined as follows: ```sql CREATE INDEX idx_composite ON my_table (int_column, string_column); ``` When I run the following query, it takes a long time to execute: ```sql SELECT * FROM my_table WHERE int_column = 123 AND string_column = 'example'; ``` I've ensured that the `int_column` is indexed properly, and I'm using MySQL 8.0.26. However, the query execution time can exceed 5 seconds, which seems excessive for such a simple lookup. To troubleshoot, I've run `EXPLAIN` on the query, and it shows that the index is being used but suggests that the performance might be hindered due to the mixed data types in the composite index: ``` EXPLAIN SELECT * FROM my_table WHERE int_column = 123 AND string_column = 'example'; ``` The output indicates a potential full table scan despite the index. I've also tried: - Rebuilding the index with `ALTER TABLE my_table DROP INDEX idx_composite, ADD INDEX idx_composite (int_column, string_column);` - Optimizing the table with `OPTIMIZE TABLE my_table;` - Testing the query with only one condition (just `int_column` or just `string_column`), which performs as expected. Could the type mismatch in the composite index be causing this issue? Should I consider separating the index for better performance, or is there a more efficient way to handle this? Any insights would be greatly appreciated! For context: I'm using Sql on Ubuntu. Any ideas what could be causing this? Any examples would be super helpful.