Performance problems with wp meta seo plugin

Hi I'm using the wp meta seo plugin for a while. I'm not sure if this is the right place for posting a problem. But I did'nt find a support or report area.

Currently I see performance issues with my server. I analysed that and found this plugin. The plugin is requesting my database with a query like this:

SELECT *
FROM wordpress_xxxx.wp_wpms_links
WHERE (link_url = '/xxxx'
AND link_url != "/"
OR type = "add_rule"
OR type = "add_custom"

With 700.000 entries this query in a simple database client takes round about 2,5 seconds and the result contains 0 rows.
So, what I see in table definition is: There is no index, not on link_url and not on type.

The link_url column is of type text. The maximal link length can be 2,083 characters, so it would be possible to redefine this column and set an index.

Would you try to fix this? Can I change this myself without having to expect any problems?

Best Regards
Westor