Re: support for MERGE

Em ter., 12 de abr. de 2022 às 10:47, Alvaro Herrera <
alvherre(at)alvh(dot)no-ip(dot)org> escreveu:

> On 2022-Apr-02, Ranier Vilela wrote:
>
> > Em sáb., 2 de abr. de 2022 às 12:01, Alvaro Herrera <
> alvherre(at)alvh(dot)no-ip(dot)org>
> > escreveu:
>
> > IMHO, actually there are bug here.
> > ExecGetChildToRootMap is clear, is possible returning NULL.
> > To discover if the map is NULL, ExecGetChildToRootMap needs to process
> > "ResultRelInfo *leaf_part_rri".
> > So, the argument "if the map is NULL, this function should not be
> called",
> > is contradictory.
>
> I was not explicit enough. I meant "if no map is needed to adjust
> columns, then this function should not be called". The caller already
> knows if it's needed or not; it doesn't depend on literally testing
> 'map'. If somebody mis-calls this function, it would have crashed, yes;
> but that's a caller bug, not this function's.
>
Thanks for the explanation.

>
> A few days ago, the community Coverity also complained about this, so I
> added an Assert that the map is not null, which should silence it.
>
Thanks for hardening this.

>
> > If the right fix is to return the original list, here is the patch
> attached.
>
> ... for a buggy caller (one that calls it when unnecessary), then yes
> this would be the correct code -- except that now the caller doesn't
> know if the returned list needs to be freed or not. So it seems better
> to avoid accumulating pointless calls to this function by just not
> coping with them.
>
Sure, it is always better to avoid doing work, unless strictly necessary.

regards,
Ranier Vilela