Rails core - Jul 2013 - Does Rails need support of `NULLS FIRST|LAST` for `ORDER BY` expression?

Hi,

after I investigated https://github.com/rails/rails/issues/11571 issue,
found that *ORDER BY ... NULLS FIRST|LAST* expression is supported 
(documented) by *ANSI*,
and implemented in PostreSQL (MySQL has another options for this feature 
and does not support for now).

To fix in full that issue *reverse_order* should generate for *"ORDER BY 
time ASC NULLS FIRST"* => "*ORDER BY time DESC NULLS LAST"*.
But adding *NULLS FIRST|LAST* which are supported only by Postgresql, will 
add more complexity for *reverse_sql_order* (
https://github.com/rails/rails/blob/master/activerecord/lib/active_record/relation/query_methods.rb#L978
)

Another way is remain current implementation and developer should use 
custom order expression by *reorder*

*topics = Topics.order(''time ASC NULLS FIRST'')*
*reversed_topics = topics.reorder(''''time DESC NULLS
LAST'')*


What do you think?
There is a simple way to do customization, and does Rails need upgraded *
reverse_order* to generate valid SQL for custom *ORDER BY* expressions?

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It''s not hard to implement an equivalent for mysql, to reverse where
nulls sort you just use ORDER by -x DESC instead of ORDER BY x ASC.  If
there''s a proper API for it in AR then it should be easy enough to
support both ANSI and Mysql implementations.

Dunno what the best API is, but I''d suggest something like
order("x", :nulls => :last).  Better than more and more string
fudging IMHO.


On 1/08/2013, at 08:40 , Paul Nikitochkin <paul.nikitochkin@gmail.com>
wrote:
> Hi,
> 
> after I investigated https://github.com/rails/rails/issues/11571 issue,
> found that ORDER BY ... NULLS FIRST|LAST expression is supported
(documented) by ANSI,
> and implemented in PostreSQL (MySQL has another options for this feature
and does not support for now).
> 
> To fix in full that issue reverse_order should generate for "ORDER BY
time ASC NULLS FIRST" => "ORDER BY time DESC NULLS LAST".
> But adding NULLS FIRST|LAST which are supported only by Postgresql, will
add more complexity for reverse_sql_order
(https://github.com/rails/rails/blob/master/activerecord/lib/active_record/relation/query_methods.rb#L978)
> 
> Another way is remain current implementation and developer should use
custom order expression by reorder
> 
> topics = Topics.order(''time ASC NULLS FIRST'')
> reversed_topics = topics.reorder(''''time DESC NULLS
LAST'')
> 
> What do you think?
> There is a simple way to do customization, and does Rails need upgraded
reverse_order to generate valid SQL for custom ORDER BY expressions?
> 
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>  
>  
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On Thu, Aug 01, 2013 at 11:07:57AM +1200, Will Bryant
wrote:
> It''s not hard to implement an equivalent for mysql, to reverse
where nulls sort you just use ORDER by -x DESC instead of ORDER BY x ASC.  If
there''s a proper API for it in AR then it should be easy enough to
support both ANSI and Mysql implementations.
> 
> Dunno what the best API is, but I''d suggest something like
order("x", :nulls => :last).  Better than more and more string
fudging IMHO.
I''d much rather it''s an option than do string parsing.

-- 
Aaron Patterson
http://tenderlovemaking.com/

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Thanks, cool!

I''m also agree with that (this option saw in sequel gem), will create
PR
for it.

On Thursday, August 1, 2013 8:21:31 AM UTC+3, Aaron Patterson
wrote:
>
> On Thu, Aug 01, 2013 at 11:07:57AM +1200, Will Bryant wrote: 
> > It''s not hard to implement an equivalent for mysql, to
reverse where
> nulls sort you just use ORDER by -x DESC instead of ORDER BY x ASC.  If 
> there''s a proper API for it in AR then it should be easy enough to
support
> both ANSI and Mysql implementations. 
> > 
> > Dunno what the best API is, but I''d suggest something like
order("x",
> :nulls => :last).  Better than more and more string fudging IMHO. 
>
> I''d much rather it''s an option than do string parsing. 
>
> -- 
> Aaron Patterson 
> http://tenderlovemaking.com/ 
>
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