Re: what does this mean: "running xacts with xcnt == 0"

On Wed, Nov 12, 2014 at 12:47 PM, Andres Freund <andres@2ndquadrant.com> wrote:
>> >> > So maybe 'Encountered xl_running_xacts record with xcnt = 0.'?
>> >>
>> >> That's not very user-facing, is it -- I mean, why bother the user with
>> >> the names of structs and members thereof?  It seems better to describe
>> >> what the condition is; something like "found point in time with no
>> >> running transaction".  Maybe "point in time" should be "WAL record"
>> >> instead.
>> >
>> > Is that really a win in clarity? When analyzing a problem I'd much
>> > rather have a concrete hint than something fuzzy.
>>
>> You can't phrase error messages in terms of internal concepts that 99%
>> of users won't understand or care about.  Like Peter says, user-facing
>> error messages need to be written in English, not C.
>
> That's not the actual message, but an errdetail() - and lots of those
> refer to internals? And it's not an error, but a log message? E.g. we
> add error contexts for wal replay errors that print the internals
> literaly?  And it's *really* helpful?

Like what?  That's the only errdetail() currently in the tree that
contains ==, for example.

I see there are three different detail messages associated with this
error message.   You don't really need these messages to be phrased in
any; it's enough to have the messages be different from each other.

1. found initial snapshot in snapbuild file
2. Transaction ID %u finished; no more running transactions.
3. running xacts with xcnt == 0

The second one follows style guidelines, but the other two do not.

I suggest:

1. Logical decoding will begin using saved snapshot.
2. Transaction ID %u finished; no more running transactions.
3. There are no running transactions.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
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