Re: Re: [COMMITTERS] pgsql: Get rid of the need for manual maintenance of the initial

On Tue, Jan 05, 2010 at 02:02:51PM -0500, Tom Lane wrote:
> Stefan Kaltenbrunner <stefan(at)kaltenbrunner(dot)cc> writes:
> > did that and it seems the problem is in the loop that does:
>
> > foreach my $row (@$data)
> > {
>
> > # To construct fmgroids.h and fmgrtab.c, we need to inspect some
> > # of the individual data fields. Just splitting on whitespace
>
> Huh. It's weird that I don't see a leak in either 5.8.7 or 5.10.1,
> which are the two closest perl versions I have handy here. I think
> this may be a platform-specific Perl bug. Still, it would be nice
> to work around it if we can.
>
> I'm not nearly good enough in Perl to be sure about the semantics
> of this loop. Is it possible that it's changing the global contents
> of the @$data structure, rather than just hacking a local copy of
> each row before pushing some values into @fmgr?
Yes, that is what would happen.
I have not read this script at all but that is how perl works...

$row is an aliased to each scalar in the list '(@$data)'

There is no copying. Copying happens on list assignment,
but not with for/foreach.

If you wanted a copy you need something like:
foreach my $row (@{[ @$data ]}) {

for a shallow copy.

Is that a problem? (I haven't read the script)

Garick

>
> regards, tom lane
>
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