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Question About WAL filename and its time stamp 3+ messages / 3 participants [nested] [flat]
* Question About WAL filename and its time stamp @ 2013-09-05 13:19 ascot.moss@gmail.com <ascot.moss@gmail.com> 0 siblings, 2 replies; 3+ messages in thread From: ascot.moss@gmail.com @ 2013-09-05 13:19 UTC (permalink / raw) To: pgsql-general general <pgsql-general@postgresql.org>; +Cc: ascot.moss@gmail.com Hi, From the pg_xlog folder, I found some files with interesting time stamps: older file names with newer timestamps, can you please advise why? Set 1: How come 0000000400000F490000008D is 10 minutes newer than 0000000400000F490000008E? -rw------- 1 111 115 16777216 Sep 4 15:28 0000000400000F490000008C -rw------- 1 111 115 16777216 Sep 4 15:27 0000000400000F490000008D <=== -rw------- 1 111 115 16777216 Sep 4 15:17 0000000400000F490000008E <==== -rw------- 1 111 115 16777216 Sep 4 15:26 0000000400000F490000008F -rw------- 1 111 115 16777216 Sep 4 15:27 0000000400000F4900000090 Set 2: why files, 0000000400000F48000000FD, 0000000400000F48000000FE and 0000000400000F4900000000, are not reused? 1) -rw------- 1 postgres postgres 16777216 Sep 4 23:07 0000000400000F48000000FA 2) -rw------- 1 postgres postgres 16777216 Sep 4 23:08 0000000400000F48000000FB 3) -rw------- 1 postgres postgres 16777216 Sep 4 23:09 0000000400000F48000000FC <=== 4) -rw------- 1 postgres postgres 16777216 Sep 4 14:47 0000000400000F48000000FD <==== 5) -rw------- 1 postgres postgres 16777216 Sep 4 14:46 0000000400000F48000000FE 6) -rw------- 1 postgres postgres 16777216 Sep 4 14:46 0000000400000F4900000000 regards= ^ permalink raw reply [nested|flat] 3+ messages in thread
* Re: Question About WAL filename and its time stamp @ 2013-09-06 02:17 Suzuki Hironobu <hironobu@interdb.jp> parent: ascot.moss@gmail.com <ascot.moss@gmail.com> 1 sibling, 0 replies; 3+ messages in thread From: Suzuki Hironobu @ 2013-09-06 02:17 UTC (permalink / raw) To: ascot.moss@gmail.com <ascot.moss@gmail.com>; +Cc: pgsql-general general <pgsql-general@postgresql.org> Hi, (13/09/05 22:19), ascot.moss@gmail.com wrote: > Hi, > > From the pg_xlog folder, I found some files with interesting time stamps: older file names with newer timestamps, can you please advise why? > > Set 1: How come 0000000400000F490000008D is 10 minutes newer than 0000000400000F490000008E? > -rw------- 1 111 115 16777216 Sep 4 15:28 0000000400000F490000008C > -rw------- 1 111 115 16777216 Sep 4 15:27 0000000400000F490000008D <=== > -rw------- 1 111 115 16777216 Sep 4 15:17 0000000400000F490000008E <==== > -rw------- 1 111 115 16777216 Sep 4 15:26 0000000400000F490000008F > -rw------- 1 111 115 16777216 Sep 4 15:27 0000000400000F4900000090 WAL files will be recycled. For example: sampledb=# select pg_xlogfile_name(pg_current_xlog_location()); pg_xlogfile_name -------------------------- 000000010000000000000004 (1 row) -rw-------. 1 postgres postgres 16777216 Sep 6 10:55 000000010000000000000001 -rw-------. 1 postgres postgres 16777216 Sep 6 10:56 000000010000000000000002 -rw-------. 1 postgres postgres 16777216 Sep 6 10:57 000000010000000000000003 -rw-------. 1 postgres postgres 16777216 Sep 6 10:58 000000010000000000000004 <--- current WAL After a few minutes, sampledb=# select pg_xlogfile_name(pg_current_xlog_location()); pg_xlogfile_name -------------------------- 000000010000000000000006 (1 row) -rw-------. 1 postgres postgres 16777216 Sep 6 11:01 000000010000000000000004 <-- Time of the last write. -rw-------. 1 postgres postgres 16777216 Sep 6 11:02 000000010000000000000005 -rw-------. 1 postgres postgres 16777216 Sep 6 11:02 000000010000000000000006 <-- current WAL -rw-------. 1 postgres postgres 16777216 Sep 6 10:55 000000010000000000000007 <-- old name is 000000010000000000000001 -rw-------. 1 postgres postgres 16777216 Sep 6 10:56 000000010000000000000008 <-- old name is 000000010000000000000002 -rw-------. 1 postgres postgres 16777216 Sep 6 10:57 000000010000000000000009 <-- old name is 000000010000000000000003 Timing of recycling depends on the situation. If the time stamp of current WAL file is the most recent compared with other WAL files, there is no contradiction. (I wonder that the time stamp of 0000000400000F490000008C is the most recent.) > Set 2: why files, 0000000400000F48000000FD, 0000000400000F48000000FE and 0000000400000F4900000000, are not reused? > 1) -rw------- 1 postgres postgres 16777216 Sep 4 23:07 0000000400000F48000000FA > 2) -rw------- 1 postgres postgres 16777216 Sep 4 23:08 0000000400000F48000000FB > 3) -rw------- 1 postgres postgres 16777216 Sep 4 23:09 0000000400000F48000000FC <=== > 4) -rw------- 1 postgres postgres 16777216 Sep 4 14:47 0000000400000F48000000FD <==== > 5) -rw------- 1 postgres postgres 16777216 Sep 4 14:46 0000000400000F48000000FE > 6) -rw------- 1 postgres postgres 16777216 Sep 4 14:46 0000000400000F4900000000 This is the specification of WAL. This specification changes from 9.3. regards -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general ^ permalink raw reply [nested|flat] 3+ messages in thread
* Re: Question About WAL filename and its time stamp @ 2013-09-06 05:22 Haribabu kommi <haribabu.kommi@huawei.com> parent: ascot.moss@gmail.com <ascot.moss@gmail.com> 1 sibling, 0 replies; 3+ messages in thread From: Haribabu kommi @ 2013-09-06 05:22 UTC (permalink / raw) To: ascot.moss@gmail.com <ascot.moss@gmail.com>; +Cc: pgsql-general general <pgsql-general@postgresql.org> On 05 September 2013 18:50 ascot.moss wrote: From the pg_xlog folder, I found some files with interesting time stamps: older file names with newer timestamps, can you please advise why? >Set 1: How come 0000000400000F490000008D is 10 minutes newer than 0000000400000F490000008E? >-rw------- 1 111 115 16777216 Sep 4 15:28 0000000400000F490000008C >-rw------- 1 111 115 16777216 Sep 4 15:27 0000000400000F490000008D <=== >-rw------- 1 111 115 16777216 Sep 4 15:17 0000000400000F490000008E <==== >-rw------- 1 111 115 16777216 Sep 4 15:26 0000000400000F490000008F >-rw------- 1 111 115 16777216 Sep 4 15:27 0000000400000F4900000090 >Set 2: why files, 0000000400000F48000000FD, 0000000400000F48000000FE and 0000000400000F4900000000, are not reused? >1) -rw------- 1 postgres postgres 16777216 Sep 4 23:07 0000000400000F48000000FA >2) -rw------- 1 postgres postgres 16777216 Sep 4 23:08 0000000400000F48000000FB >3) -rw------- 1 postgres postgres 16777216 Sep 4 23:09 0000000400000F48000000FC <=== >4) -rw------- 1 postgres postgres 16777216 Sep 4 14:47 0000000400000F48000000FD <==== >5) -rw------- 1 postgres postgres 16777216 Sep 4 14:46 0000000400000F48000000FE >6) -rw------- 1 postgres postgres 16777216 Sep 4 14:46 0000000400000F4900000000 In postgres every checkpoint end, it recycle or remove the old xlog files. During the recycle process it creates next set of xlog files Which will be used later by database operations. The files FC, FD, FE and 00 are recycled files. Now the FC file is in use because of this Reason the time stamp is different. Regards, Hari babu. ^ permalink raw reply [nested|flat] 3+ messages in thread
end of thread, other threads:[~2013-09-06 05:22 UTC | newest] Thread overview: 3+ messages (download: mbox mbox.gz follow: Atom feed) -- links below jump to the message on this page -- 2013-09-05 13:19 Question About WAL filename and its time stamp ascot.moss@gmail.com <ascot.moss@gmail.com> 2013-09-06 02:17 ` Suzuki Hironobu <hironobu@interdb.jp> 2013-09-06 05:22 ` Haribabu kommi <haribabu.kommi@huawei.com>
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