Re: UNNEST with multiple args, and TABLE with multiple funcs

On 08/14/2013 08:22 AM, Josh Berkus wrote:
> On 08/13/2013 06:54 AM, Andrew Gierth wrote:
>> Summary:
>>
>> This patch implements a method for expanding multiple SRFs in parallel
>> that does not have the surprising LCM behaviour of SRFs-in-select-list.
>> (Functions returning fewer rows are padded with nulls instead.)
> 
> BTW, if anyone is unsure of the use-case for this, I have some uses for it:
> 
> 1. denormalized data stored in same-length arrays (usually for
> compression reasons)
> 
> 2. use with PL/Python-Numpy and PL/R functions which return multiple
> arrays or 2D arrays.
> 
> In other words, I have *lots* of uses for this functionality, and I
> think the analytics crowd will like it.  Which means that I need to get
> on testing it, of course ...

Similarly, I see uses for this come up a lot, and usually have to work
around it with ugly invocations of multiple SRFs in the SELECT list in a
subquery.

I was thinking of implementing multi-argument unnest directly with `any`
parameters if I could get it to work, but hadn't started on it yet.

This looks like a really clever approach and it handles multiple
spec-compliance items. I'll grab the patch and try it out.

-- Craig Ringer                   http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training & Services