Let's say I have 10 year data, and commonly used data only the last 1 year. This data is quite big, so each table and index file is divided into several file in PGDATA/base
May not be relevant to what you asked, but if you want to keep last yeat data in a "small and fast" dataset separated (physically separated!) by old data (that's still available, but response times may vary), IMHO you should consider partitioning... https://www.postgresql.org/docs/current/static/ddl-partitioning.html
