Re: Question About WAL filename and its time stamp

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.