https://www.postgresql.org/docs/14/pgfreespacemap.html
PostgreSQL: Documentation: 14: F.27. pg_freespacemap
F.27. pg_freespacemap F.27.1. Functions F.27.2. Sample Output F.27.3. Author The pg_freespacemap module provides a means for examining the free space map …
postgresqldocumentationfpg
https://docs.postgresql.fr/14/pgfreespacemap.html
F.27. pg_freespacemap
fpg