Merging two database dumps

I have a situation with multiple postgres servers running all with the same
databases and table structure. I need to periodically export the data from
each of there then merge them all into a single server. On occasion, it's
feasible for the same record (primary key) to be stored in two or more
servers

I was using pgdump without the --insert option however I just noticed that
pgrestore will stop inserting into a table when the conflict occurs,
leaving me with an incomplete set.

Question is what are my other options to skip over the conflicting record
when merging?

From the docs, it appears that making dumps with the --insert option may be
the only way to go however performance is an issue. In this case would
dropping all indexes help?