Re: is any reason why only one columns subselect are allowed in array()?

From: "Pavel Stehule" <pavel(dot)stehule(at)gmail(dot)com>
To: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: "Sam Mason" <sam(at)samason(dot)me(dot)uk>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: is any reason why only one columns subselect are allowed in array()?
Date: 2008-11-18 18:13:54
Message-ID: 162867790811181013t20532dcai7bbb399edb1aad7e@mail.gmail.com
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2008/11/18 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:
> Sam Mason <sam(at)samason(dot)me(dot)uk> writes:
>> I've used this syntax before and got a surprising message back. I'd
>> expect to be able to do the following:
>>
>> and get the following back {"(a,1)","(b,2)"}. So I think I'm with
>> David.
>
> I concur --- if we support something like this, the behavior should be
> that you get an array of record. Pavel's proposal for a 2-D array seems
> unworkably restrictive. And I certainly don't want to end up in a
> situation where we return either a 2-D array or array of record
> depending on whether the parser thinks the column data types match ...

there are clean rules. you do array from input - when input is 1D
array, then result is 2D array, when input is record, then result is
1D array of record. Where should be problem? I see Sam proposal as
only one special case of my proposal.

Pavel

I am sorry, but you know - record type is very unfriendly to plpgsql.

>
> regards, tom lane
>
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