2010/8/7 Tom Lane <t...@sss.pgh.pa.us>:
> "David E. Wheeler" <da...@kineticode.com> writes:
>> I think that some sort of variadic pairs would be useful for this. But since
>> there is no core "ordered pair" data type, I don't think you're going to get
>> too far.
>
> It's not immediately clear to me what an ordered-pair type would get you
> that you don't get with 2-element arrays.
>
> A couple of quick experiments suggest that 2-D arrays might be the thing
> to use. They're easy to construct:
>
> regression=# select array[[1,2],[3,4]];
> array
> ---------------
> {{1,2},{3,4}}
> (1 row)
>
> and you can build them dynamically at need:
>
> regression=# select array[[1,2],[3,4]] || array[5,6];
> ?column?
> ---------------------
> {{1,2},{3,4},{5,6}}
> (1 row)
>
> This is not exactly without precedent, either: our built-in xpath()
> function appears to use precisely this approach for its namespace-list
> argument.
it's one variant, but isn't perfect
a) it expects so key and value are literals
b) it expects so all values has same types - what is usually what we
need, but not necessary
c) isn't too readable - I am sorry so I am repeating - it is same
reason, why people will prefer a VARIADIC function before function
with array - but I can accept, so this is my view of world
Regards
Pavel Stehule
>
> regards, tom lane
>
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