To be fair, the extended statistics available in PG10 are about the most primitive ones possible. If the PG10 stats help with your queries, great, but otherwise

To be fair, the extended statistics available in PG10 are about the most primitive ones possible. If the PG10 stats help with your queries, great, but otherwise it's mainly laying infrastructure for the more advanced stuff - histograms, MCV lists, expression statistics, and ultimately join statistics (which is about the main source of estimation issues). Oleg also mentioned it might be useful for JSON statistics, which would be cool. Hopefully those bits will get in faster - I first submitted the patch in 2014, just before pgconf.eu, I think. OTOH I can't really complain, because I'm shitty developer so the initial versions were far from committable. The quality requirements for PostgreSQL patches are damn high these days. BTW if you have examples of real-world queries hurt by poor estimates, report them to pgsql-performance mailing list. It's an important piece of information about what cases to look at first. Obviously, we already have already collected various queries, but having more is good.