I already finished migrating the system from oracle to postgresql. Right now, I'm trying to improve its performance - Im bringing data from another read only database that is updaded every minute. I cant push data from the oracle side to the postgresql side because the oracle database is read only.
I had a system that consist from many objects(procedures,functions..) on an oracle database. We decided to integrate that system to postgresql. That system coppied alot of big tables from a different read only oracle database and preformed on it alot of queries to produce reports. The part of getting the data is part of some procedures, I cant change it so freely. I'm searching a way to improve the perfomance of the database because I'm sure that I didnt conifgure something well. Moreover, When I run complicted queries (joint between 4 big tables and filtering) it takes alot of time and I see that the server is cacheing all my ram memory.
Probably your joins are done on Postgres side.
m.b. instead of Postgres pulling data from Oracle, you should try pushing data from Oracle to Postgres using Oracle’s Heterogeneous Services and Postgres ODBC driver. In this case you do your joins and filtering on Oracles side and just push the result set to Postgres.
That’s how I did migration from Oracle to Postgres.