database - mysql like% query is slow with full-text index

Question

I'm using a simple mysql LIKE query like this:
SELECT * FROM myTable WHERE field LIKE 'aaa%' ORDER BY field2

I have a full-text index on "field", and still it is very slow. I understood there is an option to use match. What is the difference? How? What is the best approach for my usage? Notice I'm using the "%" for everything that starts with "aaa"

UPDATE: I've ended up using something like this: SELECT
*, MATCH (name) AGAINST ('a*' IN BOOLEAN MODE) AS SCORE
FROM
users WHERE
MATCH (name) AGAINST ('a*' IN BOOLEAN MODE)
ORDER BY SCORE, popularity DESC LIMIT 4

One thing I would like to change, is not due the order by firstly by SCORE and then by my field popularity, and instead order by a simple weight function, something like 0.5*SCORE + 0.5*popularity. How?

Answer 1

LIKE does not use the full-text index. To make use of the fulltext index, you have to use match (as you said):

SELECT * 
FROM myTable 
WHERE MATCH(field) AGAINST ('aaa*' IN BOOLEAN MODE)
ORDER BY field2

The MySQL Manual has a extensive Chapter on Full-Text Search Functions.