Re: [HACKERS] MERGE SQL Statement for PG11

On Fri, Mar 23, 2018 at 6:45 AM, Peter Geoghegan <pg(at)bowt(dot)ie> wrote:

> On Thu, Mar 22, 2018 at 6:02 PM, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
> wrote:
> > Incremental development is a good thing. Trying to do everything in a
> > single commit is great when time is infinite or even merely very long,
> > but if you run out of it, which I'm sure is common, leaving some things
> > out that can be reasonable implemented in a separate patch is perfectly
> > acceptable.
>
> We're talking about something that took me less than an hour to get
> working. AFAICT, it's just a matter of tweaking the grammar, and
> adding a bit of transformWithClause() boilerplate to the start of
> transformMergeStmt().
>>
>>
>> I quickly implemented CTE support myself (not wCTE support, since
>> MERGE doesn't use RETURNING), and it wasn't tricky. It seems to work
>> when I mechanically duplicate the approach taken with other types of
>> DML statement in the parser. I have written a few tests, and so far it
>> holds up.
>>
>
> Ok, thanks. I started doing something similar, but great if you have
> already implemented. I will focus on other things for now.
>
>

I am sorry. I was under the impression that you're actually writing this
piece of code and hence did not pay much attention till now. I should have
confirmed with you instead of assuming. I think it's a bit too late now,
but I will give it a fair try tomorrow. I don't want to spend too much time
on it though given how close we are to the deadline. As Alvaro said, we can
always revisit this for pg12.

> As I've pointed out on this thread already, I'm often concerned about
> supporting functionality like this because it increases my overall
> confidence in the design. If it was genuinely hard to add WITH clause
> support, then that would probably tell us something about the overall
> design that likely creates problems elsewhere. It's easy to say that
> it isn't worth holding the patch up for WITH clause support, because
> that's true, but it's also beside the point.
>

Understood.

Thanks,
Pavan

--
Pavan Deolasee http://www.2ndQuadrant.com/
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