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

From: Garick Hamlin <ghamlin(at)isc(dot)upenn(dot)edu>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Stefan Kaltenbrunner <stefan(at)kaltenbrunner(dot)cc>, Robert Haas<robertmhaas(at)gmail(dot)com>, PostgreSQL-development<pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Re: [COMMITTERS] pgsql: Get rid of the need for manual maintenance of the initial
Date: 2010-01-05 19:37:51
Message-ID: 20100105193751.GF88668@isc.upenn.edu (view raw or flat)
Thread:
Lists: pgsql-committerspgsql-hackers
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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