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Re: plperl arginfo

From: Andrew Dunstan <andrew(at)dunslane(dot)net>
To: Garick Hamlin <ghamlin(at)isc(dot)upenn(dot)edu>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Tim Bunce <Tim(dot)Bunce(at)pobox(dot)com>
Subject: Re: plperl arginfo
Date: 2010-10-28 18:41:36
Message-ID: 4CC9C3E0.4000706@dunslane.net (view raw or flat)
Thread:
Lists: pgsql-hackers

On 10/28/2010 02:11 PM, Garick Hamlin wrote:
> On Thu, Oct 28, 2010 at 01:03:24PM -0400, Andrew Dunstan wrote:
>>
>> On 10/28/2010 12:34 PM, Tom Lane wrote:
>>> BTW, maybe we could have the best of both worlds?  Dunno about Perl,
>>> but in some languages it would be possible to instantiate the hash
>>> only if it's actually touched.  Passing the data as a hash definitely
>>> seems to fit with the spirit of things otherwise, so as long as it
>>> didn't cost cycles when not needed, I'd be in favor of that API.
>> Maybe, but I think that's getting rather beyond my perlguts-fu. I think
>> we'd need to do that via PERL_MAGIC_tied, but it's new territory for me.
>> Anyone else want to chime in?
> Warning, I don't know the plperl, I am just a perl coder.
>
> I do think all the anonymous array are worth worrying about in terms of
> performance.
>
> I don't think that tie is necessarily good for performance.  tie() is not
> generally fast.  I think you'd likely be better off writing plain accessors
> or using a function to add type info.
>
> Use an accessor for type information, like this?
> $ref->typeof($key)
>
> ...
> or perhaps use a special function?
>
> add_type_info(\%args);
>
> ...
> or if you want attibute based syntax sugar for the add_type_info() solution...
>
> my %args : pg_record(add_type_info);
>
> Again, these I don't know the plperl code, so I might be missing something
> here.
>

This wouldn't be done at the perl level. It would be done in C code. Run 
"man perlguts" and search for "Understanding the Magic of Tied Hashes 
and Arrays". The overhead in setting it up is likely to be very low 
unless I'm not understanding correctly. There might be some price paid 
when accessing the object, but that's another affair.

OTOH, a pg_get_arg_info() function would probably be a substantially 
simpler if slightly less perlish solution.

cheers

andrew

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