Re: array_length(anyarray)

On Jan9, 2014, at 23:26 , Jim Nasby  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  wrote:
>>>> On 19 December 2013 08:05, Pavel Stehule  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 length in the first place?  You can't access any elements by index, you'd need to look at array_lower().  You can't iterate over 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.  Same goes 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 was an 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 subset of all possible arrays. Otherwise we'll just add to the confusion, not avoid it.

best regards,
Florian Pflug