PostgrSQL的連線數過多，修改一下預設的連線數

https://stackoverflow.com/questions/2757549/org-postgresql-util-psqlexception-fatal-sorry-too-many-clients-already

1. First find your postgresql.conf file
2. If you don’t know where it is, query the database with the sql: SHOW config_file;
3. Mine is in: /var/lib/pgsql/data/postgresql.conf
4. Login as root and edit that file.
5. Search for the string: “max_connections”.
6. You’ll see a line that says max_connections=100.
7. Set that number bigger, check the limit for your postgresql version.
8. Restart the postgresql database for the changes to take effect.