After this brief section about indexes, there are more indexing-related features that can be added. In PostgreSQL, there is the concept of operator classes, which has already been discussed in one of the earlier chapters. The contrib module offers two extensions (namely, btree_gist and btree_gin) to add b-tree functionality to GiST and GIN indexes.
Why is that so useful? GiST indexes offer various features that are not supported by b-trees. One of those features is the ability to perform a K-Nearest Neighbor (KNN) search.
Why is that relevant? Imagine somebody is looking for data that was added yesterday around noon. So, when is that? In some cases, it might be hard to come up with boundaries, for example, ...
