Re: Re: patch: fix performance problems with repated decomprimation of varlena values in plpgsql

Pavel Stehule <pavel.stehule@gmail.com> writes:
> 2011/1/18 Tom Lane <tgl@sss.pgh.pa.us>:
>> I looked at this patch and found it fairly awkward. What is the point
>> of adding an additional flag to every variable, as opposed to just
>> forcibly detoasting during assignment?

> But detoasting on assignment isn't enought:

> for i in array_lower(a,1) .. array_upper(a,1)
> loop
>   if x < a[i] then
>     x = a[i];
>   end if;
> end loop;

> in this cycle the variable a wasn't modified. Any access to this
> variable means a detoast and decompres.

How so?  In what I'm envisioning, a would have been decompressed when it
was originally assigned to.

			regards, tom lane