Re: pg_resetxlog to clear backup start/end locations. - Mailing list pgsql-hackers

Hello,

> Ok, I'm doing modify it to reset backup locations by default and
> remove the new option '-b' to do that. Since this seems looking
> to be a bug for the poeple, I'll provide backpatches back
> to... 8.4?  (Final release of 8.4 is scheduled at July 2014)

I looked closer to pg_resetxlog and found I'm feeling discomfort
of its behavior.

"pg_resetxlog -n", which is explained in its help that "no
update, just show what would be done (for testing) ", shows
current values then values to be changed, like this.

| Current pg_control values:
| 
| pg_control version number:            942
| Catalog version number:               201406181
| Database system identifier:           6026883474640211951
| Latest checkpoint's TimeLineID:       1
| Latest checkpoint's full_page_writes: on
| Latest checkpoint's NextXID:          0/1831
| Latest checkpoint's NextOID:          32772
| Latest checkpoint's NextMultiXactId:  1
| Latest checkpoint's NextMultiOffset:  0
| Latest checkpoint's oldestXID:        1800
| Latest checkpoint's oldestXID's DB:   1
| Latest checkpoint's oldestActiveXID:  0
| Latest checkpoint's oldestMultiXid:   1
| Latest checkpoint's oldestMulti's DB: 1
| Maximum data alignment:               8
...
| Values to be changed:
| 
| First log segment after reset:        00000001000000000000000C

But "pg_resetxlog -f" made the change as below,

| *** /tmp/1.txt  2014-06-25 10:49:42.269336739 +0900
| --- /tmp/2.txt  2014-06-25 10:49:49.780266229 +0900
| ***************
| *** 5,9 ****
| ! pg_control last modified:             Wed 25 Jun 2014 10:45:20 AM JST
| ! Latest checkpoint location:           0/B8DE1A0
| ! Prior checkpoint location:            0/B8DE138
| ! Latest checkpoint's REDO location:    0/B8DE1A0
| ! Latest checkpoint's REDO WAL file:    00000001000000000000000B
| --- 5,9 ----
| ! pg_control last modified:             Wed 25 Jun 2014 10:49:46 AM JST
| ! Latest checkpoint location:           0/C000028
| ! Prior checkpoint location:            0/0
| ! Latest checkpoint's REDO location:    0/C000028
| ! Latest checkpoint's REDO WAL file:    00000001000000000000000C
| ***************
| *** 22 ****
| ! Time of latest checkpoint:            Wed 25 Jun 2014 10:45:20 AM JST
| --- 22 ----
| ! Time of latest checkpoint:            Wed 25 Jun 2014 10:49:46 AM JST

There are some changes which haven't been shown by '-n' option,
even not displayed at all. I think these should be shown by
'-n'. I suppose this is a kind of bug but fixing it seems to be a
kind of 'feature change'..

Any suggestions?


reagrds,

-- 
Kyotaro Horiguchi
NTT Open Source Software Center