Re: Support UPDATE table SET(*)=...

On Wed, Oct 15, 2014 at 3:48 AM, Atri Sharma <atri(dot)jiit(at)gmail(dot)com> wrote:
>
>
> On Wednesday, October 15, 2014, Marti Raudsepp <marti(at)juffo(dot)org> wrote:
>>
>> Hi
>>
>> On Wed, Oct 15, 2014 at 11:02 AM, Atri Sharma <atri(dot)jiit(at)gmail(dot)com> wrote:
>> > Please find attached a patch which implements support for UPDATE table1
>> > SET(*)=...
>>
>> I presume you haven't read Tom Lane's proposal and discussion about
>> multiple column assignment in UPDATE:
>> http://www.postgresql.org/message-id/1783.1399054541@sss.pgh.pa.us
>> (Assigning all columns was also discussed there)
>>
>> And there's a WIP patch:
>> http://www.postgresql.org/message-id/20930.1402931841@sss.pgh.pa.us
>
> Thanks for the links, but this patch only targets SET(*) case, which, if I
> understand correctly, the patch you mentioned doesn't directly handle (If I
> understand correctly, the target of the two patches is different).

Yeah -- in fact, there was some discussion about this exact case.
This patch solves a very important problem: when doing record
operations to move data between databases with identical schema
there's currently no way to 'update' in a generic way without building
out the entire field list via complicated and nasty dynamic SQL. I'm
not sure about the proposed syntax though; it seems a little weird to
me. Any particular reason why you couldn't have just done:

UPDATE table1 SET * = a,b,c, ...

also,

UPDATE table1 t SET t = (SELECT (a,b,c)::t FROM...);

seems cleaner than the proposed syntax for row assignment. Tom
objected though IIRC.

merlin