I'm trying to get the <-> operator to recognize a trigram index (GIST) I've set on a table. Using `EXPLAIN VERBOSE` I can see the query engine ignoring the trigram index when using the `<->` operator. However if I use the `%` operator, the index is found and used. Can you explain why this is happening? As far as I can tell from the documentation, the `<->` operator should be using the index as well.