Andrew Dunstan <andrew(at)dunslane(dot)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.
regards, tom lane