On 11/03/2014 03:24 PM, Tom Lane wrote:
Andrew Dunstan <and...@dunslane.net> writes:
     andrew=# do $x$ declare r abc; begin for i in 1 .. 10000000 loop
     select 'a','b',i into r.x,r.y,r.z; end loop; end; $x$;
     DO
     Time: 63731.434 ms
     andrew=# do $x$ declare r abc; begin for i in 1 .. 10000000 loop r
     := ('a','b',i); end loop; end; $x$;
     DO
     Time: 18744.151 ms
Is it simply because the SELECT is in effect three assignments, so it
takes nearly 3 times as long?
I think it's more likely that the second example is treated as a "simple
expression" so it has less overhead than a SELECT.

                        


Well, I accidetally left out this case:

   andrew=# do $x$ declare r abc; begin for i in 1 .. 10000000 loop
   select row('a','b',i) into r; end loop; end; $x$;
   DO
   Time: 81919.721 ms


which is slower still.

cheers

andrew



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