[avereveard]

"pg_upgrade does its best to make sure the old and new clusters are binary-compatible, e.g., by checking for compatible compile-time settings, including 32/64-bit binaries. It is important that any external modules are also binary compatible, though this cannot be checked by pg_upgrade."

This makes me very nervous tho, I've at least two exts (trigrams and gists) maybe they work, maybe not, I just prefer the ease of mind of a old fashioned dump.

[Uberphallus]

Don't take my word for it, but I think those extensions aren't considered "external" as they're part of the PGSQL distribution.

It'd be something like nominatim.so, which is external to PGSQL and (AFAIK) has its own format for certain types of data and indexes.