Is there a way to have SQL work in parallelism with two computers? Amateur here. I have a couple of the same old 4 core computers that I am trying to use to beef up some automatic query scripts that run every evening for my hobby. I recently found MPICH to have the two computers communicate with each other.  I also found documentstion that allows postresql to use more than the default number of cores (It was set at 2). I am hoping there is some way of being able to use all 8 cores to run some SQL queries.  Is this possible? Any thoughts or recommendations are appreciated.
If you want a solution using plain PostgreSQL, you will have to use sharding, that is, you will have to split the database into parts that you keep on different machines.

You can use PL/Proxy to have a single query run on all machines in parallel.