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Re: COPY (query) TO file

From: Andrew Dunstan <andrew(at)dunslane(dot)net>
To: Greg Stark <gsstark(at)mit(dot)edu>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, PFC <lists(at)peufeu(dot)com>, Tino Wildenhain <tino(at)wildenhain(dot)de>, Mark Woodward <pgsql(at)mohawksoft(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: COPY (query) TO file
Date: 2006-06-03 23:12:24
Message-ID: 44821758.5090109@dunslane.net (view raw or flat)
Thread:
Lists: pgsql-hackers

Greg Stark wrote:

>It would have been awfully nice to do be able to do
>
>SELECT ... FROM (VALUES (a,b,c),(d,e,f),(g,h,i))
>
>
>  
>
>>The trouble with supporting it for any case other than INSERT is that
>>you have to work out what the column datatypes of the construct ought
>>to be.  This is the same as the equivalent problem for UNION constructs,
>>but the UNION type resolution algorithm looks kinda ugly for thousands
>>of inputs :-(
>>    
>>
>
>I always thought UNION just decided on the type based on the first branch and
>then coerced all the others to that type. I always cast all the columns on the
>first union branch just in case.
>
>  
>

Could we get away with requiring an explicit type expression where 
there's some abiguity or uncertainty, like this

  SELECT ... FROM (VALUES (a,b,c),(d,e,f),(g,h,i)) as (a int, b text, c float) 


That's what you have to do with an SRF that returns a SETOF RECORD in the same situation, after all.


cheers

andrew

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Subject: Re: Possible TODO item: copy to/from pipe
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