pg_split_walfile_name

[Fabrice Chapuis <fabrice636861@xxxxxxxxx>]

Hi,

In the documentation, PostgreSQL: Documentation: 17: 9.28. System Administration Functions, I do not understand the position 100C in the wal filename and how the result could be C001?

Any idea?

Regards,

Fabrice

pg_split_walfile_name is useful to compute a LSN from a file offset and WAL file name, for example:

postgres=# \set file_name '000000010000000100C000AB'
postgres=# \set offset 256
postgres=# SELECT '0/0'::pg_lsn + pd.segment_number * ps.setting::int + :offset AS lsn
  FROM pg_split_walfile_name(:'file_name') pd,
       pg_show_all_settings() ps
  WHERE ps.name = 'wal_segment_size';
      lsn
---------------
 C001/AB000100
(1 row)