Keeping data safe is the top responsibility of anyone running a database. To prevent against data loss, the Cloud SQL for PostgreSQL team has developed the PostgreSQL Page Verification tool (pg_page_verification) to verify checksums on PostgreSQL data pages without having to load each page into shared buffer cache. The tool currently skips the Free Space Map (FSM), Visibility Map (VM) and pg_internal.init files since they can be regenerated. It can be run when the database process is online or offline and supports subsequent segments for tables larger than 1GB. Cloud SQL for PostgreSQL uses the tool at scale to validate backups.
./pg_page_verification -D /path/to/data/dir
This is not an official Google product.