Re: assignment vs SELECT INTO

On 11/03/2014 03:24 PM, Tom Lane wrote:
> 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.
>
>

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