Re: [HACKERS] lag(bigint,int,int), etc?

On 27 Jun 2017, at 17:06, Merlin Moncure <mmoncure@gmail.com> wrote:
>
>> On Tue, Jun 27, 2017 at 10:01 AM, Colin 't Hart <colinthart@gmail.com> wrote:
>> Hi,
>>
>> The following rather contrived example illustrates that lag(), lead()
>> (and probably other functions) can't automatically cast an integer to
>> a bigint:
>>
>> select lag(sum,1,0) over () from (select sum(generate_series) over
>> (order by generate_series) from generate_series(1,10)) x;
>> ERROR:  function lag(bigint, integer, integer) does not exist
>> LINE 1: select lag(sum,1,0) over () from (select sum(generate_series...
>>               ^
>> HINT:  No function matches the given name and argument types. You
>> might need to add explicit type casts.
>>
>>
>> I guess this is because the lag() and lead() functions take any type,
>> and hence the default must be of the same type.
>> This had me stumped for a few while until I realised that the types
>> were different.
>>
>> Would there be any way to implement an automatic conversion?
>>
>> On the off-chance that this is actually a bug, this is on 9.6.3, but
>> it also occurs on 9.3.17
>
> Why not cast the arguments?  The first and the third argument have to
> be the same, and the second argument is always int.
>
> merlin

I know that I can cast. I'm wondering if it would be possible/desirable to implement automatic casting. Automatic
castingworks already for functions defined to take bigint and you pass in an integer. But not for these functions that
takeany type. 

/Colin