[Slick1.0-RC1] Multiple field sorting

[Pradeep Kumar Mishra]

I am trying to implement sorting over two fields lets say price, rating in order of asc, desc respectively. I see the results are not appropriate and after I print the statement I see the order is reversed i.e. I am geting statement ending with order by x23.x30 desc, x2.x7 which clearly is not correct. Here is some code..

//Filter param is a list of filter parameters.

val q3 = q2.sortBy(resultSort(_, filterParams.sortTerms.head, filterParams.sortDirections.head))

    val direction = if(!filterParams.sortDirections.tail.isEmpty && filterParams.sortDirections.tail.head == "desc")

                         "desc"

                    else

                         "asc"

    val q4 = if (!filterParams.sortTerms.tail.isEmpty){

     q3.sortBy(resultSort(_, filterParams.sortTerms.tail.head, direction))

    }

    else q3

result sort is a method which will sort q2 query elements.

Is there something wrong here?  if I do sort chaining the order should be as it is i.e. in this case Ideally order by should be x2.x7, x23.x32 desc 

Thanks,

Pradeep

[Stefan Zeiger]

On 2013-02-06 23:31, Pradeep Kumar Mishra wrote:

I am trying to implement sorting over two fields lets say price, rating in order of asc, desc respectively. I see the results are not appropriate and after I print the statement I see the order is reversed i.e. I am geting statement ending with order by x23.x30 desc, x2.x7 which clearly is not correct. Here is some code..

//Filter param is a list of filter parameters.

val q3 = q2.sortBy(resultSort(_, filterParams.sortTerms.head, filterParams.sortDirections.head))

    val direction = if(!filterParams.sortDirections.tail.isEmpty && filterParams.sortDirections.tail.head == "desc")

                         "desc"

                    else

                         "asc"

    val q4 = if (!filterParams.sortTerms.tail.isEmpty){

     q3.sortBy(resultSort(_, filterParams.sortTerms.tail.head, direction))

    }

    else q3

I have no idea what your column names are supposed to be, so I'll assume that you expect .sortBy(_.a).sortBy(_.b) to generate code like "order by a, b". That would be wrong. sortBy(x => (x.a, x.b))  will do that but in .sortBy(_.a).sortBy(_.b) b wins. The sorting methods on Scala collections are stable, so Slick adds a as a secondary criterion to give you the same effect, making it "order by b, a". For non-stable sorting, a would be completely irrelevant, making it "order by b".

--
Stefan Zeiger
Typesafe - The software stack for applications that scale
Twitter: @StefanZeiger

[Pradeep Kumar Mishra]

Thanks Stefan.  Makes perfect sense to me.

Regards,

Pradeep