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yap-6.3/packages/myddas/pl/myddas_prolog2sql_optimizer.ypp
2014-01-24 19:59:42 +00:00

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:- module(myddas_prolog2sql_optimizer,[
optimize_sql/2
]).
:- use_module(lists,[
append/3,
member/2,
delete/3,
substitute/4
]).
optimize_sql([],[]).
optimize_sql([query(Proj,From,Where)|Tail],[query(Proj1,From1,Where1)|SQLTerm]):-
optimize_subquery(Proj,Proj1,From,From1,Where,Where1),
optimize_sql(Tail,SQLTerm).
% --- optimize_subquery(SQLFrom,SQLWhere) -------------------------------
%
% If there is a subquery on the query,
% uses the less number of table necessary in the
% FROM token of the SQL Statement. see(EXPLAIN (SQL statemente with subquerie) )
%
% Optimization: * All variables on the projection term must be on the outer statement
% * All variables on the outer query, must have their respective raltions on the outer query
% * Try to maintain as more possibles relations on the inner statement
% --------------------------------------------------------------------------------------
%TODO: BUG
% BEWARE WHEN THE SUBQUERY HAS NO TABLES AT THE END OF THIS OPTIMIZATION
optimize_subquery(SQLSelect,OptSelectFinal,F,F,W,W):-
once(member(agg_query(Agg,Select,From,Where,Extra),SQLSelect)),!,
optimize_subquery(Select,OptSelect,From,OptFrom,Where,OptWhere),
substitute(agg_query(Agg,Select,From,Where,Extra),SQLSelect,agg_query(Agg,OptSelect,OptFrom,OptWhere,Extra),OptSelectFinal).
optimize_subquery(SQLSelect,SQLSelect,SQLFrom,OptFrom,SQLWhere,OptWhere):-
%SQLSelect = OptSelect, % In the future, if needed optimize projection term
once(member(negated_existential_subquery(_,SubQueryRelations,_),SQLWhere))
;
once(member(existential_subquery(_,SubQueryRelations,_),SQLWhere))
,!,
add_relation(SubQueryRelations,[],RelTotalTemp),
add_relation(SQLFrom,RelTotalTemp,RelTotal),
projection_term_analysis(SQLSelect,From1,RelTotal,RelTotal1),
comparasion_analysis(SQLWhere,From1,From2,RelTotal1,RelTotal2),
delete_surplous_tables(SQLWhere,RelTotal2,OptWhere),
OptFrom = From2.
optimize_subquery(ProjTerm,ProjTerm,From,From,Where,Where).
delete_surplous_tables([negated_existential_subquery(A,_,B)|T],Rel,[negated_existential_subquery(A,Rel,B)|T]):-!.
delete_surplous_tables([existential_subquery(A,_,B)|T],Rel,[existential_subquery(A,Rel,B)|T]):-!.
delete_surplous_tables([H|T],Rel,[H|Final]):-
delete_surplous_tables(T,Rel,Final).
comparasion_analysis([],From,From,RelTotal,RelTotal).
comparasion_analysis([comp(att(Relation,_),_,att(Relation,_))|Tail],From1,[rel(Name,Relation)|FromFinal],RelTotal,RelTotalFinal):-
member(rel(Name,Relation),RelTotal),!,
delete(RelTotal,rel(Name,Relation),RelTotal1),
comparasion_analysis(Tail,From1,FromFinal,RelTotal1,RelTotalFinal).
comparasion_analysis([comp(att(Relation1,_),_,att(Relation2,_))|Tail],From1,From4,RelTotal,RelTotal3):-
comparasion_analysis(Tail,From1,From2,RelTotal,RelTotal1),
!,
(member(rel(Name,Relation1),RelTotal1) ->
delete(RelTotal1,rel(Name,Relation1),RelTotal2),
From3 = [rel(Name,Relation1)|From2]
;
RelTotal2 = RelTotal1,
From3 = From2
),
(member(rel(Name,Relation2),RelTotal2) ->
delete(RelTotal2,rel(Name,Relation1),RelTotal3),
From4 = [rel(Name,Relation2)|From3]
;
RelTotal3 = RelTotal2,
From4 = From3
).
comparasion_analysis([_|Tail],From,FromFinal,RelTotal,RelTotalFinal):-
comparasion_analysis(Tail,From,FromFinal,RelTotal,RelTotalFinal).
projection_term_analysis([],[],Relation,Relation).
projection_term_analysis([att(Relation,_)|Tail],[rel(Name,Relation)|FromFinal],RelTotal,RelTotal1):-
member(rel(Name,Relation),RelTotal),!,
delete(RelTotal,rel(Name,Relation),Residue),
projection_term_analysis(Tail,FromFinal,Residue,RelTotal1).
projection_term_analysis([_|Tail],FromFinal,RelTotal,RelTotal1):-
projection_term_analysis(Tail,FromFinal,RelTotal,RelTotal1).
add_relation([],Final,Final).
add_relation([Rel|Tail],RelTotal,RelFinal):-
not once(member(Rel,RelTotal)),!,
append(RelTotal,[Rel],RelTemp),
add_relation(Tail,RelTemp,RelFinal).
add_relation([_|Tail],RelTotal,RelFinal):-
add_relation(Tail,RelTotal,RelFinal).