In order to answer questions like that, generally, it's super helpful if you will include the "EXPLAIN" output for the query. It may also be useful to share some simple DDL stuff so we can create the tables and data you're using and try it out on our end.
In this specific case (without digging too much into this, and without the info above) I'd guess there's an index missing and probably on the field "realisation_category_id"
Steve