proposed by PostgreSQL contributor Alvaro Herrera. BRIN stands for “Block Range INdex”. A block range is a group of pages adjacent to each other, where summary information about all those pages is stored in Index.  For example, Datatypes like integers  dates where sort order is linear  can be stored as min and max [&]

https://www.percona.com/blog/2019/07/16/brin-index-for-postgresql-dont-forget-the-benefits/