How to demonstrate MVCC in Postgresql?

Question

PostgreSQL

I need to demonstrate how MVCC works in Postgresql using several parallel sessions working with the same data in a table.
Can you suggest how to do this or throw off a link to a resource explaining this?

Answer 1

t1
begin;
t2
begin;
update tablename set foo = 10;
t1
select * from tablename; -- do not wait for the lock, do not see the results of changes from t2. This only happens in MVCC.