Re: Patch to add functionality to specify ORDER BY in CREATE FUNCTION for SRFs

On Tue, Jan 6, 2015 at 12:23 PM, Atri Sharma <atri(dot)jiit(at)gmail(dot)com> wrote:

>
>>>
>>> The overhead of this patch is small. A new path is added for the
>>> preorder keys, and OrderCheck node's additional cost is pretty low, given
>>> that it only compares two rows and stores only a single row (previous row
>>> seen), hence the memory footprint is minuscule.
>>>
>>>
>> We can eliminate the new node and put onus or having the right order on
>> the user like we do with volatile setting of the function.
>>
>>
>
> That is exactly what the new node does, since we are not re sorting right
> now in case the order is wrong. Please see my explanation upthread,
> OrderCheck node's primary purpose is to check for a user error in the
> result rows order. The onus right now to give correct order is on user.
>
>
Even checking whether the output of the function is in the right order or
not, has its cost. I am suggesting that we can eliminate this cost as well.
For example, PostgreSQL does not check whether a function is really
immutable or not.

> Regards,
>
> Atri
> --
> Regards,
>
> Atri
> *l'apprenant*
>

--
Best Wishes,
Ashutosh Bapat
EnterpriseDB Corporation
The Postgres Database Company