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Re: [HACKERS] Performance testing of COPY (SELECT) TO

From: Hans-Juergen Schoenig <postgres(at)cybertec(dot)at>
To: Zoltan Boszormenyi <zboszor(at)dunaweb(dot)hu>, Andrew Dunstan <andrew(at)dunslane(dot)net>, Bruce Momjian <bruce(at)momjian(dot)us>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-patches(at)postgresql(dot)org
Subject: Re: [HACKERS] Performance testing of COPY (SELECT) TO
Date: 2006-08-28 16:49:55
Message-ID: 44F31EB3.1070706@cybertec.at (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
>>> Remember that we were talking about supporting views, not tables.  And
>>> if a view uses a slow query then you are in immediate danger of having a
>>> slow COPY.  This may not be a problem but it needs to be discussed and
>>> an agreement must be reached before introducing such a change (and not
>>> during feature freeze).
>>>       
>> COPY relname TO meant tables _and_ views to me.
>> My previous tsting showed no difference between
>> COPY table TO and COPY (SELECT * FROM table) TO.
>> Similarly a slow query defined in the view should show
>> no difference between COPY view TO and
>> COPY (SELECT * FROM view) TO.
>>     
>
> The difference is that we are giving a very clear distinction between a
> table and a view.  If we don't support the view in the direct COPY, but
> instead insist that it be passed via a SELECT query, then the user will
> be aware that it may be slow.
>   

what kind of clever customers do you have in the US? ;) i would never 
say something like that here :).
i see your point and i think it is not a too bad idea. at least some 
folks might see that there is no voodoo going on ...

> "relname" at this point may mean anything -- are you supporting
> sequences and toast tables as well?
>
>   

good point ...

>
>
> It's ugly because you are forcing the system to parse something that
> was already parsed.
>   

definitely an argument for dropping the view stuff ...

> On the other hand I don't see why you are arguing in favor of a useless
> feature whose coding is dubious; you can have _the same thing_ with nice
> code and no discussion.
>
>   

what are you referring to?

    hans


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