Re: surprising trigger/foreign key interaction

Tom Lane wrote:
> Stefan Kaltenbrunner <stefan@kaltenbrunner.cc> writes:
> > the "surprise" here was that the delete is getting silently surpressed 
> > even though the original Qual still holds and afaik should result in the 
> > row deleted.
> 
> The delete from foo acts first (since you put it in a BEFORE trigger).
> After the trigger comes back, the outer delete finds itself trying
> to delete a row that was already updated by a later-starting command in
> the same transaction.

Hmm, I misread the code when talking to Stefan on IM.  I followed the
path that heap_update returns HeapTupleUpdated, which proceeds to do
EvalPlanQual and attempt to update the updated version of the row.
However I'm guessing that what actually happens is that heap_update is
returning HeapTupleSelfUpdated instead, which the code states as
/* nothing to do */.

I imagine this is so because of some old fiddling to get semantics just
right for obscure corner cases, but it feels wrong nevertheless.

-- 
Alvaro Herrera                                http://www.CommandPrompt.com/
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