Previous discussions:

https://news.ycombinator.com/item?id=8714477 (~2 years ago, 58 comments)

https://news.ycombinator.com/item?id=8381748 (~2 years ago, 95 comments)

https://news.ycombinator.com/item?id=12605156

And this new index type for PostgreSQL:

https://github.com/postgrespro/rum