On 20 July 2017 at 21:33, Yugo Nagata <nag...@sraoss.co.jp> wrote: > On Thu, 20 Jul 2017 11:02:25 +0200 > Michael Paquier <michael.paqu...@gmail.com> wrote: > > > On Thu, Jul 20, 2017 at 10:58 AM, DEV_OPS <dev...@ww-it.cn> wrote: > > > I think you may reference to function: pg_xlogfile_name in > > > src/backend/access/transam/xlogfuncs.c, it use XLogFileName defined > in > > > src/include/access/xlog_internal.h > > > > > > #define XLogFileName(fname, tli, logSegNo) \ > > > snprintf(fname, MAXFNAMELEN, "%08X%08X%08X", tli, \ > > > (uint32) ((logSegNo) / XLogSegmentsPerXLogId), \ > > > (uint32) ((logSegNo) % XLogSegmentsPerXLogId)) > > > > > > > > > hope it's helpful for you > > > > The first 8 characters are the timeline number in hexadecimal format. > > The next 8 characters indicate a segment number, which gets > > incremented every 256 segments in hexa format. The last 8 characters > > indicate the current segment number in hexa format. > > As far as I understand, XLOG is a logical big file of 256 * 16 MB, > and this is split to multiple physical files of 16MB which are called > WAL segments. The second 8 characters indicate the id of the logical > xlog file, and the last 8 characters indicate the sequencial number of > the segment in this xlog. > <http://www.postgresql.org/mailpref/pgsql-hackers> >
You missed the timeline ID, which is the first 8 digits. -- Craig Ringer http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services
