Re: Using results from INSERT ... RETURNING

On Sun, Sep 27, 2009 at 12:40 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> Well, part of the problem is that I've not had a lot of luck trying to
>> understand how the executor really works (what's a tuple table slot
>> and why do we need to know in advance how many of them there are?).
>
> You know, that's actually a really good question.  There is not, as far
> as I can see, much advantage to keeping the Slots in an array.  We could
> perfectly well keep them in a List and eliminate the notational overhead
> of having to count them in advance.  There'd be a bit more palloc
> overhead (for the list cells) but avoiding the counting work would more
> or less make up for that.

Heh. I was actually asking an even stupider question, which is why do
we need to keep all of them in ANY centrally known data structure?
What operation do we perform that requires us to find all of the
exstant TTS?

...Robert