Re: master in standby mode croaks

On Sun, Apr 18, 2010 at 9:58 PM, Fujii Masao <masao(dot)fujii(at)gmail(dot)com> wrote:
> On Sun, Apr 18, 2010 at 7:52 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>> On Sat, Apr 17, 2010 at 6:41 PM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
>>> On Sat, 2010-04-17 at 17:44 -0400, Robert Haas wrote:
>>>
>>>> > I will change the error message.
>>>>
>>>> I gave a good deal of thought to trying to figure out a cleaner
>>>> solution to this problem than just changing the error message and
>>>> failed.  So let's change the error message.  Of course I'm not quite
>>>> sure what we should change it TO, given that the situation is the
>>>> result of an interaction between three different GUCs and we have no
>>>> way to distinguish which one(s) are the problem.
>>>
>>> "You need all three" covers it.
>>
>> Actually you need standby_connections and either archive_mode=on or
>> max_wal_senders>0, I think.
>
> Right.
>
> First of all, I wonder why the latter two need to affect the decision of
> whether additional information is written to WAL for HS. How about just
> removing XLogIsNeeded() condition from XLogStandbyInfoActive()?

Bad idea, I think. If XLogIsNeeded() is returning false and
XLogStandbyInfoActive() is returning true, the resulting WAL will
still be unusable for HS, at least AIUI.

...Robert