If the wal segment size is larger than the wal_buffers parameter value, the value of the wal_buffers_full column of pg_stat_wal increases after database shutdown and startup.
pg_controldata | grep "Bytes per WAL segment"
Bytes per WAL segment: 1073741824
wal_buffers = 16MB
---- DB shutdown and restart
postgres=# select * from pg_stat_wal; wal_records | wal_fpi | wal_bytes | wal_buffers_full | wal_write | wal_sync | wal_write_time | wal_sync_time | stats_reset
-------------+---------+-----------+------------------+-----------+----------+----------------+---------------+------------------------------- 6165 | 462 | 14071380 | 126070 | 126115 | 40 | 0 | 0 | 2022-04-25 14:28:04.746772+09
(1 row)
If wal_buffers size and wal_segment size are the same, wal_buffers_full column does not increase.
pg_controldata | grep "Bytes per WAL segment"
Bytes per WAL segment: 16777216
wal_buffers = 16MB
postgres=# select * from pg_stat_wal; wal_records | wal_fpi | wal_bytes | wal_buffers_full | wal_write | wal_sync | wal_write_time | wal_sync_time | stats_reset
-------------+---------+-----------+------------------+-----------+----------+----------------+---------------+------------------------------- 6161 | 461 | 14062929 | 0 | 39 | 36 | 0 | 0 | 2022-04-25 12:13:35.838092+09
(1 row)
Is this a bug?
The postgreSQL version currently in use is 14.2, and the database was restarted without performing DML and DDL.
I wonder if it doesn't matter if the values of wal_buffers and wal-segsize are different.
