%
% Data Cube Aggregates
%
% Haixun Wang, hxwang@cs.ucla.edu

%%
database( {
	sales(Year:integer, Quarter:integer, Month:integer, Day:integer, S:integer)
} ).

%%
export p(P).

%%
p(cube<(mysum, S, [Y,Q,M,D])>)<-sales(Y,Q,M,D,S).

single(cube, (Agg, C, X), (Agg, X, V)) <- init_cube(Agg, C, X, V).

init_cube(Agg, C, [_|XT], [YH|YT]) <-
    single(Agg, C, YH),
    init_cube(Agg, C, XT, YT).

init_cube(Agg, C, [], []).
    
multi(cube, (Agg, C, [XsH|XsT]),
	    (Agg, [XoH|XoT], [YoH|YoT]), 
	    (Agg, [XsH|XT], [YH|YT])) <-
    XsH=XoH,
    multi(Agg, C, YoH, YH),
    multi(cube, (Agg, C, XsT), (Agg, XoT, YoT), (Agg, XT, YT)).

multi(cube, (Agg, C, [XsH|XsT]), 
	    (Agg, [XoH|_], _),
	    (Agg, [XsH|XsT], Y)) <-
    XsH~=XoH,
    init_cube(Agg, C, [XsH|XsT], Y).

multi(cube, (Agg, _, []), _, (Agg, [], [])).

return(cube, nil, (_, Xo, Yo), (Xo, Yo)).

return(cube, (_, C, X), (_, Xo, Yo), (Xo, Y))<-
    Xo~=X,
    blankequals(Xo, X, Yo, Y).

blankequals([XoH|XoT], [XsH|XsT], [YoH|YoT], ['?'|YT])<-
    XoH=XsH,
    blankequals(XoT, XsT, YoT, YT).

blankequals([XoH|XoT], [XsH|XsT], Yo, Y)<-
    XoH~=XsH,
    Y=Yo.

blankequals([],[],Y,Y).

single(mysum, X, X).
multi(mysum, Xs, Xo, X)<-X=Xs+Xo.