Improve query execution times with extended statistics

[otbutz]

I recently stumbled across the following blog post and vaguely remembered that we had talked at some point about certain columns having a correlation with each other:

https://www.crunchydata.com/blog/hacking-the-postgres-statistics-tables-for-faster-queries#extended-statistics

https://www.postgresql.org/docs/current/sql-createstatistics.html

Perhaps this can be utilised to achieve better query execution times.

[lonvia]

I've looked into those a while ago and didn't find them to be really relevant for Nominatim. They mostly help with column correlations and I don't think we have any queries there where the query planner goes wrong.