Re: [BUGS] Status of issue 4593

Peter Eisentraut wrote:
> On Tuesday 06 January 2009 02:03:14 Tom Lane wrote:
>> I don't think there's a bug here, at least not in the sense that it
>> isn't Operating As Designed.  But it does seem like we could do with
>> some more/better documentation about exactly how FOR UPDATE works.
>> The sequence of operations is evidently a bit more user-visible than
>> I'd realized.
> 
> Well, if the effect of ORDER BY + FOR UPDATE is "it might in fact not be 
> ordered", then it's pretty broken IMO.  It would be pretty silly by analogy 
> for example, if the effect of GROUP BY + FOR UPDATE were "depending on 
> concurrent events, it may or may not be fully grouped".

I can see two ways forward:

1) We document bluntly that ORDER BY + FOR UPDATE can return unordered 
results, or

2) We prohibit ORDER BY + FOR UPDATE, like we do with a number of other 
clauses.  (There would be no loss of functionality, because you can run 
the query a second time in the transaction with ORDER BY.)

Comments?