Hi,

Last year, I was looking for the MAL definition of group_concat and
Nik Schuiling gave me the MAL definition which is below.

We compile MonetDB from source and this definition was working on
MonetDB-11.19.9 (Oct2014-SP2). Since this version, there has been a
number of newer versions of MonetDB. So, I was trying to upgrade our
system to the latest version of MonetDB (11.21.13). After the
installation of the newer version, I ran:

select "DataSetId", group_concat("FieldName") from datasetmarkermeta
group by "DataSetId";

from mclient interface and got the following error message:

TypeException:kddart.subgroup_concat[5]:'algebra.uselect' undefined
in:     TIDs:any := algebra.uselect(g:bat[:oid,:oid],grpid:oid);
MALException:kddart.subgroup_concat[0]:Error in cloned function
TypeException:user.s2_1[15]:'kddart.subgroup_concat' undefined in:
X_27:bat[:oid,:str] :=
kddart.subgroup_concat(X_26:bat[:oid,:str],X_16:bat[:oid,:oid],r1_16:bat[:oid,:oid],true:bit);
program contains errors

It says algebra.uselect function is not defined. How do I fix this problem?



group_concat MAL definition start
-------------------------------------------

module kddart;

command group_concat(b:bat[:oid,:str]):str
address KDDARTgroup_concat
comment "Mal kddart";

function group_concat(b:bat[:oid, :str]):str;

       value := "";

       barrier (h, t) := iterator.new(b);

              value := value + t;

              value := value + "";

              redo (h, t) := iterator.next(b);

       exit (h, t);

       return value;

end group_concat;



function subgroup_concat(b:bat[:oid,:any_1],g:bat[:oid,:oid],e:bat[:oid,:any_2],skip_nils:bit)
:bat[:oid,:str];

       nw := aggr.count(e);

       nl := calc.lng(nw);

       bn := bat.new(:oid, :str, nl);



       # check 'e' has some values - this is the list of group IDs in the head

       # 'g' is the group to the data BAT head ID mapping

       # 'b' is the data column BAT that we are aggregating over

       barrier (grpid, t) := iterator.new(e);



              # select GID from TID->GID map to get matching TIDs

              TIDs := algebra.uselect(g,grpid);



              # get DATA for matching TIDs

              b_data := algebra.kintersect(b,TIDs);



              # aggregate

              grpval := group_concat(b_data);



              # Store the result for this group

              bat.insert(bn, grpid, grpval);



              redo (grpid, t) := iterator.next(e);

       exit (grpid, t);

       return bn;



end subgroup_concat;
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