Re: array_length(anyarray)

On Jan9, 2014, at 23:26 , Jim Nasby <jim@nasby.net> wrote:
> On 1/9/14, 11:08 AM, Marko Tiikkaja wrote:
>> On 1/9/14 5:44 PM, Florian Pflug wrote:
>>> On Jan9, 2014, at 14:57 , Dean Rasheed <dean.a.rasheed@gmail.com> wrote:
>>>> On 19 December 2013 08:05, Pavel Stehule <pavel.stehule@gmail.com> wrote:
>>>>> length should be irrelevant to fact so array starts from 1, 0 or anything
>>>>> else
>>>>
>>>> Yes, this should just return the number of elements, and 0 for an empty array.
>>>
>>> +1. Anything that complains about arrays whose lower bound isn't 1 really
>>> needs a *way* less generic name than array_length().
>>
>> Problem is, if you're operating on an array which could have a lower bound that isn't 1, why would you look at the
lengthin the first place?  You can't access any elements by index, you'd need to look at array_lower().  You can't
iterateover the array by index, you'd need to do  array_lower() .. array_lower() + array_length(), which doesn't make
sense. And then there's the myriad of stuff you can do with unnest() without actually having to look at the length.
Samegoes for multi-dimensional arrays: you have even less things you can do there with only a length. 
>>
>> So if we give up these constraints, we also make this function completely useless.
>
> I'm generally opposed to creating code that doesn't support the full featureset of something (in this case,
array_lower()<>1).But in this case I hope we can all agree that allowing the user to set an arbitrary array lower bound
wasan enormous mistake. 

No doubt.

> While we might not be able to ever completely remove that behavior, I find the idea of throwing an error to be highly
enticing.
>
> Plus, as Marko said, this function is pretty useless for non-1-based arrays.

That I doubt, but...

> I do agree that the name is probably too generic for this though.

this one is actually my main complaint. The name needs to very clearly mark such a function as dealing only with a
subsetof all possible arrays. Otherwise we'll just add to the confusion, not avoid it. 

best regards,
Florian Pflug