Re: Update with subselect sometimes returns wrong result

On 2013-12-18 19:13:43 -0300, Alvaro Herrera wrote:
> I'm not sure about the added assert that the tuple cannot possibly be
> locked.  I fear cursors provide strange ways to access at tuples.

I don't see how, the EPQ machinery should have ensured we're looking at
the most recent version. Also, pretty fundamentally, we have to be the
only locker, otherwise the optimization wouldn't be applicable in this
way.

> In any case I think it's easy to handle the case by doing something like
>     is_update |= ISUPDATE_from_mxstatus(old_status);
> and remove the Assert().

I think I'd rather have the chance to see the pathway to that, than try
to handle it. I think we have pretty little chance of doing so correctly
if we don't know how it can happen.

Greetings,

Andres Freund

--
 Andres Freund                       http://www.2ndQuadrant.com/
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