<-> Operator on Trigram Index

[Jeffrey Kamei]

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.