How to transfer data from one database to another on the fly?

Question

PostgreSQL

There is a task:
PostgreSQL 9.6.6
For testing and troubleshooting, after users request, copy the actual data to the test database and work with it until a solution is found. But you need to copy so that users continue to work at this moment and do not feel that they are doing something with the database.
Help solve this problem.

Answer 1

pg_dump / pg_basebackup => pg_restore .
If not the whole database is needed, transfer separate tables, it will be faster.

Answer 2

postgresql.leopard.in.ua/html
hot backup or replication