How to get the total size of a Postgresql cluster (the sum of the size of all databases on the server)?

Question

PostgreSQL

How to get the total size of the Postgresql cluster (the sum of the size of all databases on the server) using sql query?

Answer 1

select sum(pg_catalog.pg_database_size(d.datname)) from pg_catalog.pg_database d;

That's just the total size of the cluster is not the same as the sum of the size of all databases. The cluster size is counted as du -s from $PGDATA