Re: final patch - plpgsql: for-in-array

2010/11/18 Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>:
> 2010/11/18 Cédric Villemain <cedric(dot)villemain(dot)debian(at)gmail(dot)com>:
>> 2010/11/18 Robert Haas <robertmhaas(at)gmail(dot)com>:
>>> On Thu, Nov 18, 2010 at 10:24 AM, Merlin Moncure <mmoncure(at)gmail(dot)com> wrote:
>>>> On Thu, Nov 18, 2010 at 12:47 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>>>>> Merlin Moncure <mmoncure(at)gmail(dot)com> writes:
>>>>>> On Wed, Nov 17, 2010 at 7:08 PM, Jaime Casanova <jaime(at)2ndquadrant(dot)com> wrote:
>>>>>>> i will start the review of this one... but before that sorry for
>>>>>>> suggesting this a bit later but about using UNNEST as part of the
>>>>>>> sintax?
>>>>>
>>>>>> Does for-in-array do what unnset does?
>>>>>
>>>>> Yes, which begs the question of why bother at all.  AFAICS this patch
>>>>> simply allows you to replace
>>>>>
>>>>>        for x in select unnest(array_value) loop
>>>>>
>>>>> with
>>>>>
>>>>>        for x in unnest array_value loop
>>>>>
>>>>> (plus or minus a parenthesis or so).  I do not think we need to add a
>>>>> bunch of code and create even more syntactic ambiguity (FOR loops are
>>>>> already on the hairy edge of unparsability) to save people from writing
>>>>> "select".
>>>>
>>>> Pavel's performance argument is imnsho valid. arrays at present are
>>>> the best way to pass data around functions and any optimizations here
>>>> are very welcome.  Given that, is there any way to mitigate your
>>>> concerns on the syntax side?
>>>
>>> Can we get the performance benefit any other way?  I hate to think
>>> that it will still be slow for people using the already-supported
>>> syntax.
>>
>> If you are able to make unnest() outputting 1st row without detoasting
>> last field.
>>
>> I think if we have :
>> #define DatumGetTextPSlice(X,m,n)   ((text *) PG_DETOAST_DATUM_SLICE(X,m,n))
>> but for array, most is done
>>
>> Pavel, am I correct ?
>
> yes, it can help, but still if you iterate over complete array, you
> have to do n - detoast ops.

sure.

>
> Pavel
>
>>
>>>
>>> --
>>> Robert Haas
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>>
>>
>>
>> --
>> Cédric Villemain               2ndQuadrant
>> http://2ndQuadrant.fr/     PostgreSQL : Expertise, Formation et Support
>>
>

--
Cédric Villemain               2ndQuadrant
http://2ndQuadrant.fr/     PostgreSQL : Expertise, Formation et Support