Once you insert something into this table, a page is allocated in the buffer cache to hold that new information, and a standard 8 KB block is allocated on disk. Now we make an insert on the table t and check if the block is dirty:
pgbench=# INSERT into t(i) values (0);INSERT 0 1bash-4.2$ ls -l $PGDATA/base/16384/16399-rw-------. 1 postgres postgres 8192 24 feb 16.48 base/16384/16399pgbench=# SELECT reldatabase,relfilenode,relblocknumber,isdirty,usagecountFROM pg_buffercache WHERE relfilenode=16399;reldatabase | relfilenode | relblocknumber | isdirty | usagecount-------------+-------------+----------------+---------+------------16384 |16399 |0 | t|1
Now make another insert and then check again if the block ...
