RE: [HACKERS] copyObject() ?

Hello all,

> -----Original Message-----
> From: Tom Lane [mailto:tgl(at)sss(dot)pgh(dot)pa(dot)us]
> Sent: Wednesday, February 24, 1999 12:16 AM
> To: Hiroshi Inoue
> Cc: pgsql-hackers
> Subject: Re: [HACKERS] copyObject() ?
>
>
> "Hiroshi Inoue" <Inoue(at)tpf(dot)co(dot)jp> writes:
> > AFAIC the relation between objects is not copied correctly
> > by copyObject() (i.e the same pointers to an object are copied
> > to different pointers by copyObject()).
>
> True, but it seems irrelevant to me --- as Jan Wieck was just pointing
> out, no code should ever depend on pointer-equality in parse trees or
> plan trees anyway.
>

If multiple references are not necessary,why we don't allocate diffrent
objects which have equal contents from the start ?

It seems very difficult to prevent developpers from using the following
fact implicitly.

The same pointers always point the equal contents.
^^^^^^^^

Different pointers (as copyObject() currently generates) which have
equal contents may have different contents some time.
Isn't it a significant differnce ?

> > There is a way to maintain the list of (old,new) pairs during
> > copyObject() operations.
>
> I think we'd be better off fixing any places that mistakenly assume
> pointer compare is sufficient. You didn't say which version you were
> testing,

My environment is v6.4.2.
OK,I would test my cases again after the release of 6.5-BETA(v6.4.3?).

TIA

Hiroshi Inoue
Inoue(at)tpf(dot)co(dot)jp