Hi Dru,

your solution works but it adds one more expensive operation and that
will make it slower, especially when data is big. As I mentioned
earlier, another solution would be to create an implementation that is
oblivious of the "display differences" between an int and a decimal.

On Mon, Nov 11, 2013 at 8:01 AM, Dru Nelson <drudru@gmail.com> wrote:
>
> Hi,
>
> While thinking about this in the morning yesterday, I came up with a
> solution. First let me explain a bit more about the challenge.
>
> I was implementing percentile_cont for a contract project. I added the
> syntax to the parser. On the backend I was using dense_rank as my initial
> template. Because dense_rank takes ANY_1, it would receive either a flt or
> int BAT. I thought i had everything working great until i worked with a
> decimal column. Because the decimal type is just an int type scaled, and the
> BAT doesn't record this, I was stuck. The window function generates a result
> based on the values (vs dense_rank just needing to know ordinality)
>
> My solution was to modify the AST after the parse to inject a CAST to a dbl
> on the OVER portion. It was not my ideal solution, since it will force an
> intermediate to be created for any type that isn't a double. None the less,
> the MAL optimizers work correctly and the function handles all types.
>
> Best,
>
> Dru
>
>
>
>
> On Sat, Nov 9, 2013 at 8:22 AM, Lefteris <lsidir@gmail.com> wrote:
>>
>> I second that! Are you sure that you cannot come up with an
>> alternative algorithm for your aggregation that does not need this
>> information (and possibly be faster) ?
>>
>> On Sat, Nov 9, 2013 at 11:26 AM, Stefan Manegold <Stefan.Manegold@cwi.nl>
>> wrote:
>> > Hi Dru,
>> >
>> > the decimal scale information is only maintained in the SQL catalog and
>> > given that decimals are stored as integers in MonetDB, neither the
>> > MonetDB
>> > kernel,
>> > nor MAL usually need to know about decimals or their scale.
>> >
>> > Hence, the question is, whether/why your aggregate functions would need
>> > to
>> > know about
>> > decimals or their scale?
>> >
>> > Best,
>> > Stefan
>> >
>> >
>> > Dru Nelson <drudru@gmail.com> wrote:
>> >>
>> >> HI,
>> >>
>> >> I"m working on writing an aggregate in in C that is a MAL function.
>> >> I've
>> >> run into a problem with decimal types.
>> >>
>> >> I've noticed that when I inspect the BAT inputs for various types, they
>> >> are coerced to
>> >> simpler types. (flt,dbl -> dbl). (int, decimal -> int). There is also
>> >> no
>> >> other information in the BAT structure to see the type.
>> >>
>> >> I notice that a SQL select gets the type info passed in as parameters
>> >> for
>> >> the 'exportValue' output.
>> >>
>> >> For example:
>> >>
>> >> >  sql.exportValue(1,".","second_single_value","decimal",9,3,8,_4,"");
>> >>
>> >> How can I get this type information ('decimal', etc.) passed into my
>> >> function?
>> >>
>> >> Dru
>> >>
>> >> ________________________________
>> >>
>> >> developers-list mailing list
>> >> developers-list@monetdb.org
>> >> https://www.monetdb.org/mailman/listinfo/developers-list
>> >
>> >
>> > --
>> > | Stefan.Manegold@CWI.nl | Database Architectures (DA) |
>> > | www.CWI.nl/~manegold | Science Park 123 (L321) |
>> > | +31 (0)20 592-4212 | 1098 XG Amsterdam (NL) |
>> >
>> > _______________________________________________
>> > developers-list mailing list
>> > developers-list@monetdb.org
>> > https://www.monetdb.org/mailman/listinfo/developers-list
>> >
>> _______________________________________________
>> developers-list mailing list
>> developers-list@monetdb.org
>> https://www.monetdb.org/mailman/listinfo/developers-list
>
>
>
> _______________________________________________
> developers-list mailing list
> developers-list@monetdb.org
> https://www.monetdb.org/mailman/listinfo/developers-list
>
_______________________________________________
developers-list mailing list
developers-list@monetdb.org
https://www.monetdb.org/mailman/listinfo/developers-list