Re: cardinality() - Mailing list pgsql-hackers

From Andrew Dunstan
Subject Re: cardinality()
Date
Msg-id 49AAAA26.3080901@dunslane.net
Whole thread Raw
In response to Re: cardinality()  (Grzegorz Jaskiewicz <gj@pointblue.com.pl>)
Responses Re: cardinality()  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-hackers

Grzegorz Jaskiewicz wrote:
>
> On 1 Mar 2009, at 00:52, Andrew Dunstan wrote:
>
>>
>> We seem to have acquired a cardinality() function with almost no 
>> discussion, and it has semantics that are a bit surprising to me. I 
>> should have thought cardinality(array) would be the total number of 
>> elements in the array. Instead, it seems it is a synonym for 
>> array_length(array,1). Is that *really* what the standard says?
>
> any difference between array_upper(array,1), and cardinality ?
> Standart just says something like:
>
> cardinality (a collection):
> - The number of elements in that collection.
> - Those elements need not necessarily have distinct values.
> - The objects to which this concept applies includes tables and the 
> values of collection types.
>

Well, I think that's a definition of the term as used in the standard, 
rather than of a function. But in any case, I think it goes in the right 
direction, and the semantics of our new function (as well as the docs) 
are misleading.

I'm also a bit concerned that I could not find any real discussion of 
this new function at all on this list, so our processes seem to have 
slipped a bit.

cheers

andrew


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