To keep indexes in memory, is large enough effective_cache_sizeenough?

Hi!

Related to my other email (size of index in memory),

Other questions,
Q: To keep _index(es)_ in memory, is large enough effective_cache_size enough?
Q: Size of shared_buffers does not matter regarding keeping index in memory?

Or have I missed something, does it matter (to keep indexes in memory)?

Background info: I have plans to use hash indexes: very large amount of data in db tables, but (e.g. hash) indexes could be kept in memory.

I am using PostgreSQL 10. I could start to use PostgreSQL 11, after it has been released.

Best Regards, Sam