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