Re: dblink_error_message return value

On 09/25/2018 01:50 PM, Joe Conway wrote:
> On 08/08/2018 11:57 AM, Tom Lane wrote:
>> =?utf-8?q?PG_Doc_comments_form?= <noreply@postgresql.org> writes:
>>> The following documentation comment has been logged on the website:
>>> Documentation says:
>> 
>>> Return Value
>>> Returns last error message, or an empty string if there has been no error in
>>> this connection.
>>> Which is invalid.
>>> Actually it returns 'OK' string if no error was raised.
>> 
>> Good catch!  The code's quite clear about it, but the SGML docs need
>> fixed.
> 
> 
> As mentioned on the nearby thread, will fix. I suppose this ought to be
> back-patched.
> 
> 
>>> Secondly
>>> dblink_is_busy must be first called to make dblink_error_message returns an
>>> error message. (Tested on 9.6.9)
>> 
>> Meh.  I see what you're getting at here, I think, but that seems like a
>> completely wrong/misleading statement of the issue.  Joe, can you think of
>> better phraseology?
> 
> Maybe a note, something like this?
> ------------
> When asynchronous queries are initiated by dblink_send_query(), the
> error message associated with the connection might not get updated until
> the server's response message is consumed. This typically means that
> dblink_is_busy() or dblink_get_result() should be called prior to
> dblink_error_message(), so that any error generated by the asynchronous
> query() will be visible.
> ------------

And now with the corresponding patch attached.

Thoughts/comments?

Joe
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