Re: Update low-level backup documentation to match actual behavior

On Tue, Aug 29, 2017 at 10:59 PM, David Steele <david(at)pgmasters(dot)net> wrote:
> Hi Robert,
>
> On 8/25/17 4:03 PM, David Steele wrote:
>> On 8/25/17 3:26 PM, Robert Haas wrote:
>>> On Fri, Aug 25, 2017 at 3:21 PM, David Steele <david(at)pgmasters(dot)net>
>>> wrote:
>>>> No problem. I'll base it on your commit to capture any changes you
>>>> made.
>>>
>>> Thanks, but you incorporated everything I wanted in response to my
>>> first review -- so I didn't tweak it any further.
>>
>> Thank you for committing that. I'll get the 9.6 patch to you early next
>> week.
>
> Attached is the 9.6 patch. It required a bit more work in func.sgml
> than I was expecting so have a close look at that. The rest was mostly
> removing irrelevant hunks.

+ switch to the next WAL segment. On a standby, it is not possible to
+ automatically switch WAL segments, so you may wish to run
+ <function>pg_switch_wal</function> on the primary to perform a manual
+ switch. The reason for the switch is to arrange for
[...]
+ WAL segments have been archived. If write activity on the primary
is low, it
+ may be useful to run <function>pg_switch_wal</> on the primary in order to
+ trigger an immediate segment switch of the last required WAL
It seems to me that both portions are wrong. There is no archiving
wait on standbys for 9.6, and pg_stop_backup triggers by itself the
segment switch, so saying that enforcing pg_switch_wal on the primary
is moot. pg_switch_xlog has been renamed to pg_switch_wal in PG10, so
the former name applies.
--
Michael