1385 lines
44 KiB
Prolog
1385 lines
44 KiB
Prolog
% -*- Mode: Prolog -*-
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% --------------------------------------------------------------------------------------
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%
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% This Prolog to SQL compiler may be distributed free of charge provided that it is
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% not used in commercial applications without written consent of the author, and
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% that the copyright notice remains unchanged.
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%
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% (C) Copyright by Christoph Draxler, Munich
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% Version 1.1 of Dec. 21st 1992
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%
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% I would like to keep in my hands the further development and distribution of the
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% compiler. This does not mean that I don't want other people to suggest or even
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% implement improvements - quite on the contrary: I greatly appreciate contributions
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% and if they make sense to me I will incorporate them into the compiler (with due
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% credits given!).
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%
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% For further development of the compiler, address your requests, comments and
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% criticism to the author:
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%
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% Christoph Draxler
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% CIS Centre for Information and Speech Processing
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% Ludwig-Maximilians-University Munich
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% Wagmuellerstr. 23
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% D 80538 Munich
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% Tel : ++49 / +89 / 211 06 64 (-60)
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% Fax : ++49 / +89 / 211 06 74
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% Mail: draxler@cis.uni-muenchen.de
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%
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%
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% A report describing the implementation is available upon request from the
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% author.
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%
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%
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% RELEASE INFORMATION
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% ===================
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% Current version is v. 1.1 of Dec. 21st 1992.
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% Version 1.0 Sept. 3 1992
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% --------------------------------------------------------------------------------------
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:- module(myddas_prolog2sql,[
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translate/3,
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queries_atom/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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]).
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:- use_module(myddas_prolog2sql_optimizer,[
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optimize_sql/2
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]).
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% --------------------------------------------------------------------------------------
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%
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% Top level predicate translate/3 organizes the compilation and constructs a
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% Prolog term representation of the SQL query.
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%
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% --------------------------------------------------------------------------------------
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#ifdef MYDDAS_STATS
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translate(ProjectionTerm,DatabaseGoal,SQLQueryTermOpt):-
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c_db_stats_walltime(Start),
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translate_(ProjectionTerm,DatabaseGoal,SQLQueryTermOpt),
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c_db_stats_walltime(End),
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c_db_stats_translate(Start,End).
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translate_(ProjectionTerm,DatabaseGoal,SQLQueryTermOpt):-
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#else
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translate(ProjectionTerm,DatabaseGoal,SQLQueryTermOpt):-
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#endif
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% --- initialize variable identifiers and range variables for relations -----
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init_gensym(var),
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init_gensym(rel),
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% --- tokenize projection term and database goal ----------------------------
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tokenize_term(DatabaseGoal,TokenDatabaseGoal),
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tokenize_term(ProjectionTerm,TokenProjectionTerm),
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% --- lexical analysis: reordering of goals for disjunctive normalized form -
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disjunction(TokenDatabaseGoal,Disjunction),
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% --- code generation ---------------------------------------------------------------
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query_generation(Disjunction,TokenProjectionTerm,SQLQueryTerm),
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% --- optimize sql ------------------------------------------------------------------
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optimize_sql(SQLQueryTerm,SQLQueryTermOpt).
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% --- disjunction(Goal,Disjunction) ----------------------------------------------------
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%
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% turns original goal into disjunctive normalized form by computing all conjunctions
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% and collecting them in a list
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%
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% --------------------------------------------------------------------------------------
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disjunction(Goal,Disjunction):-
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findall(Conjunction,linearize(Goal,Conjunction),Disjunction).
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% --- linearize(Goal,ConjunctionList) --------------------------------------------------
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%
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% Returns a conjunction of base goals for a complex disjunctive or conjunctive goal
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% Yields several solutions upon backtracking for disjunctive goals
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%
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% --------------------------------------------------------------------------------------
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linearize(((A,B),C),(LinA,(LinB,LinC))):-
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% --- transform left-linear to right-linear conjunction (',' is associative) ----
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linearize(A,LinA),
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linearize(B,LinB),
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linearize(C,LinC).
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linearize((A,B),(LinA,LinB)):-
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A \= (_,_),
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% --- make sure A is not a conjunction ------------------------------------------
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linearize(A,LinA),
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linearize(B,LinB).
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% ILP
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%linearize((A;B),LinA):-
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linearize((A;_),LinA):-
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linearize(A,LinA).
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% ILP
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%linearize((A;B),LinB):-
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linearize((_;B),LinB):-
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linearize(B,LinB).
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linearize(not A, not LinA):-
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linearize(A,LinA).
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linearize(Var^A, Var^LinA):-
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linearize(A,LinA).
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linearize(A,A):-
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A \= (_,_),
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A \= (_;_),
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A \= _^_,
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A \= not(_).
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% --- tokenize_term(Term,TokenizedTerm) -------------------------------------------------
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%
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% If Term is a
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%
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% - variable, then this variable is instantiated with a unique identifier
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% of the form '$var$'(VarId), and TokenizedTerm is bound to the same
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% term '$var$'(VarId).
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%
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% - constant, then TokenizedTerm is bound to '$const$'(Term).
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%
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% - complex term, then the term is decomposed, its arguments are tokenized,
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% and TokenizedTerm is bound to the result of the composition of the original
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% functor and the tokenized arguments.
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%
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% --------------------------------------------------------------------------------------
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tokenize_term('$var$'(VarId),'$var$'(VarId)):-
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var(VarId),
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% --- uninstantiated variable: instantiate it with unique identifier.
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gensym(var,VarId).
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tokenize_term('$var$'(VarId),'$var$'(VarId)):-
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nonvar(VarId).
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tokenize_term(Constant,'$const$'(Constant)):-
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nonvar(Constant),
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functor(Constant,_,0).
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tokenize_term(Term,TokenizedTerm):-
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nonvar(Term),
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Term \= '$var$'(_),
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Term \= '$const$'(_),
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Term =.. [Functor|Arguments],
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Arguments \= [],
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tokenize_arguments(Arguments,TokenArguments),
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TokenizedTerm =.. [Functor|TokenArguments].
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% --- tokenize_arguments(Arguments,TokenizedArguments) ---------------------------------
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%
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% organizes tokenization of arguments by traversing list and calling tokenize_term
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% for each element of the list.
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%
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% --------------------------------------------------------------------------------------
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tokenize_arguments([],[]).
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tokenize_arguments([FirstArg|RestArgs],[TokFirstArg|TokRestArgs]):-
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tokenize_term(FirstArg,TokFirstArg),
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tokenize_arguments(RestArgs,TokRestArgs).
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% --- query_generation(ListOfConjunctions, ProjectionTerm, ListOfQueries) --------------
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%
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% For each Conjunction translate the pair (ProjectionTerm,Conjunction) to an SQL query
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% and connect each such query through a UNION-operator to result in the ListOfQueries.
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%
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% A Conjunction consists of positive or negative subgoals. Each subgoal is translated
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% as follows:
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% - the functor of a goal that is not a comparison operation is translated to
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% a relation name with a range variable
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% - negated goals are translated to NOT EXISTS-subqueries with * projection
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% - comparison operations are translated to comparison operations in the WHERE-clause
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% - aggregate function terms are translated to aggregate function (sub)queries
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%
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% The arguments of a goal are translated as follows:
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% - variables of a goal are translated to qualified attributes
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% - variables occurring in several goals are translated to equality comparisons
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% (equi join) in the WHERE-clause
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% - constant arguments are translated to equality comparisons in the WHERE-clause
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%
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% Special treatment of arithmetic functions:
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% - arithmetic functions are identified through the Prolog is/2 operator
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% - an arithmetic function may contain an unbound variable only on its left side
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% - the right side of the is/2 operator may consist of
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% * bound variables (bound through occurrence within a positive database goal, or
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% bound through preceeding arithmetic function), or of
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% * constants (numbers, i.e. integers, reals)
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%
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% The following RESTRICTION holds:
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%
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% - the binding of variables follows Prolog: variables are bound by positive base goals
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% and on the left side of the is/2 predicate - comparison operations, negated goals
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% and right sides of the is/2 predicate do not return variable bindings and may even
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% require all arguments to be bound for a safe evaluation.
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%
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% --------------------------------------------------------------------------------------
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:- dynamic attribute/4.
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query_generation([],_,[]).
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query_generation([Conjunction|Conjunctions],ProjectionTerm,[Query|Queries]):-
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projection_term_variables(ProjectionTerm,InitDict),
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( Conjunction =.. [once|Arguments] ->
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[Args] = Arguments,
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translate_conjunction(Args,SQLFrom,SQLWhereTemp,InitDict,Dict),
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append(SQLWhereTemp,[once],SQLWhere)
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;
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translate_conjunction(Conjunction,SQLFrom,SQLWhere,InitDict,Dict)
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),
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translate_projection(ProjectionTerm,Dict,SQLSelect),
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Query = query(SQLSelect,SQLFrom,SQLWhere),
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query_generation(Conjunctions,ProjectionTerm,Queries).
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% --- translate_goal(Goal,SQLFrom,SQLWhere,Dict,NewDict) -------------------------------
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%
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% translates a
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%
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% - positive database goal to the associated FROM- and WHERE clause of an SQL query
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% - a negated goal to a negated existential subquery
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% - an arithmetic goal to an arithmetic expression or an aggregate function query
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% - a comparison goal to a comparison expression
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% - a negated comparison goal to a comparison expression with the opposite comparison
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% operator
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%
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% --------------------------------------------------------------------------------------
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translate_goal(SimpleGoal,[SQLFrom],SQLWhere,Dict,NewDict):-
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% --- positive goal binds variables - these bindings are held in the dictionary -----
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functor(SimpleGoal,Functor,Arity),
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translate_functor(Functor,Arity,SQLFrom),
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SimpleGoal =.. [Functor|Arguments],
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translate_arguments(Arguments,SQLFrom,1,SQLWhere,Dict,NewDict).
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translate_goal(Result is Expression,[],SQLWhere,Dict,NewDict):-
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translate_arithmetic_function(Result,Expression,SQLWhere,Dict,NewDict).
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translate_goal(not NegatedGoals,[],SQLNegatedSubquery,Dict,Dict):-
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% --- negated goals do not bind variables - hence Dict is returned unchanged --------
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functor(NegatedGoals,Functor,_),
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not comparison(Functor,_),
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translate_conjunction(NegatedGoals,SQLFrom,SQLWhere,Dict,_),
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SQLNegatedSubquery = [negated_existential_subquery([*],SQLFrom,SQLWhere)].
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translate_goal(not ComparisonGoal,[],SQLCompOp,Dict,Dict):-
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% --- comparison operations do not bind variables - Dict is returned unchanged ------
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ComparisonGoal =.. [ComparisonOperator,LeftArg,RightArg],
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comparison(ComparisonOperator,SQLOperator),
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negated_comparison(SQLOperator,SQLNegOperator),
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translate_comparison(LeftArg,RightArg,SQLNegOperator,Dict,SQLCompOp).
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%% EXAMPLE: db_prolog_select([Gene1],(once((eval(Gene1,_,_),exists(eval(Gene1),eval(Gene1,_,_)))))).
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translate_goal(exists(ProjectionTerm,ExistsGoals),SQLFrom,SQLExistsSubquery,Dict,Dict):-
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% --- exists goals do not bind variables - hence Dict is returned unchanged --------
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functor(ExistsGoals,Functor,_),
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not comparison(Functor,_),
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translate_projection(ProjectionTerm,Dict,SQLSelect),
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translate_conjunction(ExistsGoals,SQLFrom,SQLWhere,Dict,_),
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SQLExistsSubquery = [existential_subquery(SQLSelect,SQLFrom,SQLWhere)].
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translate_goal(exists(ExistsGoals),SQLFrom,SQLExistsSubquery,Dict,Dict):-
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% --- exists goals do not bind variables - hence Dict is returned unchanged --------
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functor(ExistsGoals,Functor,_),
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not comparison(Functor,_),
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translate_conjunction(ExistsGoals,SQLFrom,SQLWhere,Dict,_),
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SQLExistsSubquery = [existential_subquery([*],SQLFrom,SQLWhere)].
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translate_goal(ComparisonGoal,[],SQLCompOp,Dict,Dict):-
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% --- comparison operations do not bind variables - Dict is returned unchanged ------
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ComparisonGoal =.. [ComparisonOperator,LeftArg,RightArg],
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comparison(ComparisonOperator,SQLOperator),
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translate_comparison(LeftArg,RightArg,SQLOperator,Dict,SQLCompOp).
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%DISTINCT
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translate_goal(distinct(Goal),List,SQL,Dict,DistinctDict):-!,
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translate_goal(Goal,List,SQL,Dict,NewDict),
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add_distinct_statement(NewDict,DistinctDict).
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%DEBUG
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add_distinct_statement(Dict,Dict):-
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append([_],[1,2],_).
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% --- translate_conjunction(Conjunction,SQLFrom,SQLWhere,Dict,NewDict) -----------------
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%
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% translates a conjunction of goals (represented as a list of goals preceeded by
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% existentially quantified variables) to FROM- and WHERE-clause of an SQL query.
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% A dictionary containing the associated SQL table and attribute names is built up
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% as an accumulator pair (arguments Dict and NewDict)
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%
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% --------------------------------------------------------------------------------------
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translate_conjunction('$var$'(VarId)^Goal,SQLFrom,SQLWhere,Dict,NewDict):-
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#ifdef DEBUG_TRANSLATE
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write('translate_conjuntion clause 1'),nl,
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#endif
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% --- add info on existentially quantified variables to dictionary here -------------
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add_to_dictionary(VarId,_,_,_,existential,Dict,TmpDict),
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translate_conjunction(Goal,SQLFrom,SQLWhere,TmpDict,NewDict).
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translate_conjunction(Goal,SQLFrom,SQLWhere,Dict,NewDict):-
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#ifdef DEBUG_TRANSLATE
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write('translate_conjuntion clause 2'),nl,
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#endif
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Goal \= (_,_),
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translate_goal(Goal,SQLFrom,SQLWhere,Dict,NewDict).
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translate_conjunction((Goal,Conjunction),SQLFrom,SQLWhere,Dict,NewDict):-
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#ifdef DEBUG_TRANSLATE
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write('translate_conjuntion clause 3'),nl,
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#endif
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translate_goal(Goal,FromBegin,WhereBegin,Dict,TmpDict),
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translate_conjunction(Conjunction,FromRest,WhereRest,TmpDict,NewDict),
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append(FromBegin,FromRest,SQLFrom),
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append(WhereBegin,WhereRest,SQLWhere).
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% --- translate_arithmetic_function(Result,Expression,SQLWhere,Dict,NewDict) -----------
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%
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% Arithmetic functions (left side of is/2 operator is bound to value of expression on
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% right side) may be called with either
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%
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% - Result unbound: then Result is bound to the value of the evaluation of Expression
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% - Result bound: then an equality condition is returned between the value of Result
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% and the value of the evaluation of Expression.
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%
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% Only the equality test shows up in the WHERE clause of an SQLquery.
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%
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% --------------------------------------------------------------------------------------
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translate_arithmetic_function('$var$'(VarId),Expression,[],Dict,NewDict):-
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% assigment of value of arithmetic expression to variable - does not
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% show up in WHERE-part, but expression corresponding to
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% variable must be stored in Dict for projection translation
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evaluable_expression(Expression,Dict,ArithExpression,Type),
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add_to_dictionary(VarId,is,ArithExpression,Type,all,Dict,NewDict).
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translate_arithmetic_function('$var$'(VarId),Expression,ArithComparison,Dict,Dict):-
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% --- test whether left side evaluates to right side: return equality comparison ----
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% Left side consists of qualified attribute, i.e. range variable must not be
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% arithmetic operator is/2
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lookup(VarId,Dict,PrevRangeVar,PrevAtt,_),
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not (PrevRangeVar = is),
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% test whether type of attribute is numeric - if not, there's no sense in
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% continuing the translation
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%type_compatible(PrevType,number),
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evaluable_expression(Expression,Dict,ArithExpression,_),
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%type_compatible(ExprType,number),
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ArithComparison = [comp(att(PrevRangeVar,PrevAtt),'=',ArithExpression)].
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translate_arithmetic_function('$var$'(VarId),Expression,ArithComparison,Dict,Dict):-
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% --- test whether left side evaluates to right side: return equality comparison ----
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% Left side consists of arithmetic expression, i.e. VarId is stored in Dict as
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% belonging to arithmetic expression which is expressed as RangeVar-argument
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% of lookup returning is/2. Type information is implicit through the is/2 functor
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lookup(VarId,Dict,is,LeftExpr,_),
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%type_compatible(Type,number),
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evaluable_expression(Expression,Dict,RightExpr,_),
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%type_compatible(ExprType,number),
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ArithComparison = [comp(LeftExpr,'=',RightExpr)].
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translate_arithmetic_function('$const$'(Constant),Expression,ArithComparison,Dict,Dict):-
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% --- is/2 used to test whether left side evaluates to right side -------------------
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get_type('$const$'(Constant),_),
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%type_compatible(ConstantType,number),
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evaluable_expression(Expression,Dict,ArithExpression,_),
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%type_compatible(ExprType,number),
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ArithComparison = [comp('$const$'(Constant),'=',ArithExpression)].
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% --- translate_comparison(LeftArg,RightArg,CompOp,Dict,SQLComparison) ---------
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%
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% translates the left and right arguments of a comparison term into the
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% appropriate comparison operation in SQL. The result type of each
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% argument expression is checked for type compatibility
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%
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% ------------------------------------------------------------------------------
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translate_comparison(LeftArg,RightArg,CompOp,Dict,Comparison):-
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evaluable_expression(LeftArg,Dict,LeftTerm,_),
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evaluable_expression(RightArg,Dict,RightTerm,_),
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%type_compatible(LeftArgType,RightArgType),
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Comparison = [comp(LeftTerm,CompOp,RightTerm)].
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% --- translate_functor(Functor,QualifiedTableName) ------------------------------------
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%
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% translate_functor searches for the matching relation table name for
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% a given functor and creates a unique range variable to result in
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% a unique qualified relation table name.
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%
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% --------------------------------------------------------------------------------------
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translate_functor(Functor,Arity,rel(TableName,RangeVariable)):-
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relation(Functor,Arity,TableName),
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gensym(rel,RangeVariable).
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% --- translate_arguments(Arguments,RelTable,ArgPos,Conditions,Dict) -------------------
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%
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% translate_arguments organizes the translation of term arguments. One
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% term argument after the other is taken from the list of term arguments
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% until the list is exhausted.
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%
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% --------------------------------------------------------------------------------------
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translate_arguments([],_,_,[],Dict,Dict).
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translate_arguments([Arg|Args],SQLTable,Position,SQLWhere,Dict,NewDict):-
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translate_argument(Arg,SQLTable,Position,Where,Dict,TmpDict),
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NewPosition is Position + 1,
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translate_arguments(Args,SQLTable,NewPosition,RestWhere,TmpDict,NewDict),
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append(Where,RestWhere,SQLWhere).
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% --- translate_argument(Argument,RelTable,Position,Condition,Dict) --------------------
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%
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% The first occurrence of a variable leads to its associated SQL attribute information
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% to be recorded in the Dict. Any further occurrence creates an equi-join condition
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% between the current attribute and the previously recorded attribute.
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% Constant arguments always translate to equality comparisons between an attribute and
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% the constant value.
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%
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% --------------------------------------------------------------------------------------
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translate_argument('$var$'(VarId),rel(SQLTable,RangeVar),Position,[],Dict,NewDict):-
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attribute(Position,SQLTable,Attribute,Type),
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add_to_dictionary(VarId,RangeVar,Attribute,Type,all,Dict,NewDict).
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translate_argument('$var$'(VarId),rel(SQLTable,RangeVar),Position,AttComparison,Dict,Dict):-
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% --- Variable occurred previously - retrieve first occurrence data from dictionary -
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lookup(VarId,Dict,PrevRangeVar,PrevAtt,_),
|
|
attribute(Position,SQLTable,Attribute,_),
|
|
% type_compatible(PrevType,Type),
|
|
AttComparison = [comp(att(RangeVar,Attribute),=,att(PrevRangeVar,PrevAtt))].
|
|
|
|
translate_argument('$const$'(Constant),rel(SQLTable,RangeVar),Position,ConstComparison,Dict,Dict):-
|
|
% --- Equality comparison of constant value and attribute in table ------------------
|
|
attribute(Position,SQLTable,Attribute,_),
|
|
%get_type('$const$'(Constant),ConstType),
|
|
%type_compatible(ConstType,Type),
|
|
ConstComparison = [comp(att(RangeVar,Attribute),=,'$const$'(Constant))].
|
|
|
|
|
|
|
|
|
|
|
|
% --- projection_term_variables(ProjectionTerm,Dict) -----------------------------------
|
|
%
|
|
% extracts all variables from the ProjectionTerm and places them into the
|
|
% Dict as a dict/4 term with their Identifier, a non instantiated RangeVar and
|
|
% Attribute argument, and the keyword existential for the type of quantification
|
|
%
|
|
% --------------------------------------------------------------------------------------
|
|
|
|
%% ERRO??
|
|
%projection_term_variables('$const(_)$',[]).
|
|
projection_term_variables('$const$'(_),[]).
|
|
|
|
projection_term_variables('$var$'(VarId),[dict(VarId,_,_,_,existential)]).
|
|
|
|
projection_term_variables(ProjectionTerm,ProjectionTermVariables):-
|
|
ProjectionTerm =.. [Functor|ProjectionTermList],
|
|
not (Functor = '$var$'),
|
|
not (ProjectionTermList = []),
|
|
projection_list_vars(ProjectionTermList,ProjectionTermVariables).
|
|
|
|
|
|
projection_list_vars([],[]).
|
|
projection_list_vars(['$var$'(VarId)|RestArgs],[dict(VarId,_,_,_,existential)|RestVars]):-
|
|
projection_list_vars(RestArgs,RestVars).
|
|
projection_list_vars(['$const$'(_)|RestArgs],Vars):-
|
|
projection_list_vars(RestArgs,Vars).
|
|
|
|
|
|
|
|
|
|
|
|
|
|
% --------------------------------------------------------------------------------------
|
|
% RESTRICTION! ProjectionTerm underlies the following restrictions:
|
|
%
|
|
% - ProjectionTerm must have a functor other than the built-in
|
|
% operators, i.e. ',',';', etc. are not allowed
|
|
%
|
|
% - only variables and constants are allowed as arguments,
|
|
% i.e. no structured terms
|
|
%
|
|
% --------------------------------------------------------------------------------------
|
|
|
|
translate_projection('$var$'(VarId),Dict,SelectList):-
|
|
projection_arguments(['$var$'(VarId)],SelectList,Dict).
|
|
|
|
translate_projection('$const$'(Const),_,['$const$'(Const)]).
|
|
|
|
translate_projection(ProjectionTerm,Dict,SelectList):-
|
|
ProjectionTerm =.. [Functor|Arguments],
|
|
not (Functor = '$var$'),
|
|
not (Functor = '$const$'),
|
|
not (Arguments = []),
|
|
projection_arguments(Arguments,SelectList,Dict).
|
|
|
|
|
|
|
|
projection_arguments([],[],_).
|
|
|
|
projection_arguments([Arg|RestArgs],[Att|RestAtts],Dict):-
|
|
retrieve_argument(Arg,Att,Dict),
|
|
projection_arguments(RestArgs,RestAtts,Dict).
|
|
|
|
|
|
|
|
|
|
% - retrieve_argument(Argument,SQLAttribute,Dictionary) --------------------------------
|
|
%
|
|
% retrieves the mapping of an argument to the appropriate SQL construct, i.e.
|
|
%
|
|
% - qualified attribute names for variables in base goals
|
|
% - arithmetic expressions for variables in arithmetic goals
|
|
% - constant values for constants
|
|
%
|
|
% --------------------------------------------------------------------------------------
|
|
|
|
retrieve_argument('$var$'(VarId),Attribute,Dict):-
|
|
lookup(VarId,Dict,TableName,AttName,_),
|
|
(
|
|
TableName = is ->
|
|
Attribute = AttName
|
|
;
|
|
Attribute = att(TableName,AttName)
|
|
).
|
|
|
|
retrieve_argument('$const$'(Constant),'$const$'(Constant),_).
|
|
|
|
|
|
|
|
|
|
|
|
% --- lookup(Key,Dict,Value) -----------------------------------------------------------
|
|
|
|
lookup(VarId,Dict,RangeVar,Attribute,Type):-
|
|
member(dict(VarId,RangeVar,Attribute,Type,Quant),Dict),
|
|
(
|
|
Quant = all ->
|
|
true
|
|
;
|
|
nonvar(RangeVar),
|
|
nonvar(Attribute)
|
|
).
|
|
|
|
|
|
|
|
% --- add_to_dictionary(Key,RangeVar,Attribute,Quantifier,Dict,NewDict) ----------------
|
|
|
|
add_to_dictionary(Key,RangeVar,Attribute,Type,_,Dict,Dict):-
|
|
member(dict(Key,RangeVar,Attribute,Type,existential),Dict).
|
|
|
|
add_to_dictionary(Key,RangeVar,Attribute,Type,Quantifier,Dict,NewDict):-
|
|
not member(dict(Key,_,_,_,_),Dict),
|
|
NewDict = [dict(Key,RangeVar,Attribute,Type,Quantifier)|Dict].
|
|
|
|
|
|
|
|
|
|
% --- aggregate_function(AggregateFunctionTerm,Dict,AggregateFunctionQuery) ------------
|
|
%
|
|
% aggregate_function discerns five Prolog aggregate function terms: count, avg, min,
|
|
% max, and sum. Each such term is has two arguments: a variable indicating the attribute
|
|
% over which the function is to be computed, and a goal argument which must contain in
|
|
% at least one argument position the variable:
|
|
%
|
|
% e.g. avg(Seats,plane(Type,Seats))
|
|
%
|
|
% These aggregate function terms correspond to the SQL built-in aggregate functions.
|
|
%
|
|
% RESTRICTION: AggregateGoal may only be conjunction of (positive or negative) base
|
|
% goals
|
|
%
|
|
% --------------------------------------------------------------------------------------
|
|
|
|
aggregate_function(AggregateFunctionTerm,Dict,AggregateFunctionExpression):-
|
|
AggregateFunctionTerm =..[AggFunctor,AggVar,AggGoal],
|
|
aggregate_functor(AggFunctor,SQLFunction),
|
|
conjunction(AggGoal,AggConjunction),
|
|
aggregate_query_generation(SQLFunction,AggVar,AggConjunction,Dict,AggregateFunctionExpression).
|
|
|
|
|
|
conjunction(Goal,Conjunction):-
|
|
disjunction(Goal,[Conjunction]).
|
|
|
|
|
|
|
|
|
|
% --- aggregate_query_generation(Function,FunctionVariable,AggGoal,Dict,AggregateQuery)
|
|
%
|
|
% compiles the function variable (representing the attribute over which the aggregate
|
|
% function is to be computed) and the aggregate goal (representing the selection and
|
|
% join conditions for the computation of the aggregate function) to an SQL aggregate
|
|
% function subquery.
|
|
%
|
|
% --------------------------------------------------------------------------------------
|
|
|
|
% ILP
|
|
% aggregate_query_generation(count,'$const$'('*'),AggGoal,Dict,AggregateQuery):-
|
|
% translate_conjunction(AggGoal,SQLFrom,SQLWhere,Dict,TmpDict),
|
|
% AggregateQuery = agg_query(Function,(count,['$const$'(*)]),SQLFrom,SQLWhere,[]).
|
|
|
|
aggregate_query_generation(count,'$const$'('*'),AggGoal,Dict,AggregateQuery):-
|
|
translate_conjunction(AggGoal,SQLFrom,SQLWhere,Dict,_),
|
|
|
|
% ATTENTION! It is assumed that in count(*) aggregate query terms there cannot be
|
|
% free variables because '*' stands for "all arguments"
|
|
|
|
AggregateQuery = agg_query(_,(count,['$const$'(*)]),SQLFrom,SQLWhere,[]).
|
|
|
|
%DISTINCT
|
|
aggregate_query_generation(countdistinct,'$const$'('*'),AggGoal,Dict,AggregateQuery):-
|
|
translate_conjunction(AggGoal,SQLFrom,SQLWhere,Dict,_),
|
|
|
|
% ATTENTION! It is assumed that in count(*) aggregate query terms there cannot be
|
|
% free variables because '*' stands for "all arguments"
|
|
|
|
AggregateQuery = agg_query(_,(countdistinct,['$const$'(*)]),SQLFrom,SQLWhere,[]).
|
|
|
|
|
|
aggregate_query_generation(Function,FunctionVariable,AggGoal,Dict,AggregateQuery):-
|
|
translate_conjunction(AggGoal,SQLFrom,SQLWhere,Dict,TmpDict),
|
|
|
|
% --- only variables occurring in the aggregate goal are relevant to the translation
|
|
% of the function variable and the free variables in the goal.
|
|
% Thus subtract from TmpDict all entries of Dict
|
|
set_difference(TmpDict,Dict,AggDict),
|
|
|
|
translate_projection(FunctionVariable,AggDict,SQLSelect),
|
|
translate_grouping(FunctionVariable,AggDict,SQLGroup),
|
|
AggregateQuery = agg_query(Function,SQLSelect,SQLFrom,SQLWhere,SQLGroup).
|
|
|
|
|
|
|
|
|
|
% --- translate_grouping(FunctionVariable,Dict,SQLGroup) -------------------------------
|
|
%
|
|
% finds the free variables in the aggregate function term and collects their
|
|
% corresponding SQL qualified attributes in the SQLGroup list.
|
|
%
|
|
% --------------------------------------------------------------------------------------
|
|
|
|
translate_grouping(FunctionVariable,Dict,SQLGroup):-
|
|
free_vars(FunctionVariable,Dict,FreeVariables),
|
|
translate_free_vars(FreeVariables,SQLGroup).
|
|
|
|
|
|
|
|
|
|
% --- free_vars(FunctionVariable,Dict,FreeVarList) -------------------------------------
|
|
%
|
|
% A Variable is free if it neither occurs as the FunctionVariable, nor is stored as
|
|
% existentially quantified (through ^/2 in the original goal) in the dictionary
|
|
%
|
|
% FreeVars contains for each variable the relevant attribute and relation information
|
|
% contained in the dictionary
|
|
%
|
|
% --------------------------------------------------------------------------------------
|
|
|
|
% ILP
|
|
% free_vars(FunctionVariable,Dict,FreeVarList):-
|
|
% projection_term_variables(FunctionVariable,FunctionVariableList),
|
|
% findall((Var,Table,Attribute),
|
|
% (member(dict(Var,Table,Attribute,Type,all),Dict),
|
|
% not member(dict(Var,_,_,_,_),FunctionVariableList)
|
|
% ),
|
|
% FreeVarList).
|
|
free_vars(FunctionVariable,Dict,FreeVarList):-
|
|
projection_term_variables(FunctionVariable,FunctionVariableList),
|
|
findall((Var,Table,Attribute),
|
|
(member(dict(Var,Table,Attribute,_,all),Dict),
|
|
not member(dict(Var,_,_,_,_),FunctionVariableList)
|
|
),
|
|
FreeVarList).
|
|
|
|
|
|
% --- function_variable_list(FunctionVariable,FunctionVariableList) --------------------
|
|
%
|
|
% extracts the list of variables which occur in the function variable term
|
|
%
|
|
% RESTRICTION: FunctionVariable may only contain one single variable.
|
|
%
|
|
% --------------------------------------------------------------------------------------
|
|
|
|
function_variable_list('$var$'(VarId),[VarId]).
|
|
|
|
|
|
|
|
|
|
% --- translate_free_vars(FreeVars,SQLGroup) -------------------------------------------
|
|
%
|
|
% translates dictionary information on free variables to SQLGroup of aggregate
|
|
% function query
|
|
%
|
|
% --------------------------------------------------------------------------------------
|
|
|
|
translate_free_vars([],[]).
|
|
% ILP
|
|
%translate_free_vars([(VarId,Table,Attribute)|FreeVars],[att(Table,Attribute)|SQLGroups]):-
|
|
translate_free_vars([(_,Table,Attribute)|FreeVars],[att(Table,Attribute)|SQLGroups]):-
|
|
translate_free_vars(FreeVars,SQLGroups).
|
|
|
|
|
|
|
|
|
|
% --- evaluable_expression(ExpressionTerm,Dictionary,Expression,Type) --------------------
|
|
%
|
|
% evaluable_expression constructs SQL arithmetic expressions with qualified attribute names
|
|
% from the Prolog arithmetic expression term and the information stored in the dictionary.
|
|
%
|
|
% The type of an evaluable function is returned in the argument Type.
|
|
%
|
|
% The dictionary is not changed because it is used for lookup only.
|
|
%
|
|
|
|
evaluable_expression(AggregateFunctionTerm,Dictionary,AggregateFunctionExpression,number):-
|
|
aggregate_function(AggregateFunctionTerm,Dictionary,AggregateFunctionExpression).
|
|
|
|
evaluable_expression(LeftExp + RightExp,Dictionary,LeftAr + RightAr,number):-
|
|
evaluable_expression(LeftExp,Dictionary,LeftAr,number),
|
|
evaluable_expression(RightExp,Dictionary,RightAr,number).
|
|
|
|
evaluable_expression(LeftExp - RightExp,Dictionary,LeftAr - RightAr,number):-
|
|
evaluable_expression(LeftExp,Dictionary,LeftAr,number),
|
|
evaluable_expression(RightExp,Dictionary,RightAr,number).
|
|
|
|
evaluable_expression(LeftExp * RightExp,Dictionary,LeftAr * RightAr,number):-
|
|
evaluable_expression(LeftExp,Dictionary,LeftAr,number),
|
|
evaluable_expression(RightExp,Dictionary,RightAr,number).
|
|
|
|
evaluable_expression(LeftExp / RightExp,Dictionary, LeftAr / RightAr,number):-
|
|
evaluable_expression(LeftExp,Dictionary,LeftAr,number),
|
|
evaluable_expression(RightExp,Dictionary,RightAr,number).
|
|
|
|
evaluable_expression('$var$'(VarId),Dictionary,att(RangeVar,Attribute),Type):-
|
|
lookup(VarId,Dictionary,RangeVar,Attribute,Type),
|
|
RangeVar \= is.
|
|
|
|
evaluable_expression('$var$'(VarId),Dictionary,ArithmeticExpression,Type):-
|
|
lookup(VarId,Dictionary,is,ArithmeticExpression,Type).
|
|
|
|
evaluable_expression('$const$'(Const),_,'$const$'(Const),ConstType):-
|
|
get_type('$const$'(Const),ConstType).
|
|
|
|
|
|
|
|
|
|
|
|
% --------------------------------------------------------------------------------------
|
|
%
|
|
% Output to screen predicates - rather crude at the moment
|
|
%
|
|
% --------------------------------------------------------------------------------------
|
|
|
|
|
|
% --- printqueries(Code) ---------------------------------------------------------------
|
|
|
|
printqueries([Query]):-
|
|
nl,
|
|
print_query(Query),
|
|
write(';'),
|
|
nl,
|
|
nl.
|
|
|
|
printqueries([Query|Queries]):-
|
|
not (Queries = []),
|
|
nl,
|
|
print_query(Query),
|
|
nl,
|
|
write('UNION '),
|
|
nl,
|
|
printqueries(Queries).
|
|
|
|
|
|
|
|
% --- print_query(QueryCode) -----------------------------------------------------------
|
|
|
|
print_query(query([agg_query(Function,Select,From,Where,Group)],_,_)):-
|
|
% --- ugly rule here: aggregate function only in SELECT Part of query ----
|
|
!,
|
|
print_query(agg_query(Function,Select,From,Where,Group)).
|
|
|
|
print_query(query(Select,From,Where)):-
|
|
print_clause('SELECT',Select,','),
|
|
nl,
|
|
print_clause('FROM',From,','),
|
|
nl,
|
|
print_clause('WHERE',Where,'AND'),
|
|
nl.
|
|
|
|
print_query(agg_query(Function,Select,From,Where,Group)):-
|
|
print_clause('SELECT',Function,Select,','),
|
|
nl,
|
|
print_clause('FROM',From,','),
|
|
nl,
|
|
print_clause('WHERE',Where,'AND'),
|
|
nl,
|
|
print_clause('GROUP BY',Group,',').
|
|
|
|
print_query(negated_existential_subquery(Select,From,Where)):-
|
|
write('NOT EXISTS'),
|
|
nl,
|
|
write('('),
|
|
print_clause('SELECT',Select,','),
|
|
nl,
|
|
print_clause('FROM',From,','),
|
|
nl,
|
|
print_clause('WHERE',Where,'AND'),
|
|
nl,
|
|
write(')').
|
|
|
|
print_query(existential_subquery(Select,From,Where)):-
|
|
write('EXISTS'),
|
|
nl,
|
|
write('('),
|
|
print_clause('SELECT',Select,','),
|
|
nl,
|
|
print_clause('FROM',From,','),
|
|
nl,
|
|
print_clause('WHERE',Where,'AND'),
|
|
nl,
|
|
write(')').
|
|
|
|
|
|
|
|
|
|
% --- print_clause(Keyword,ClauseCode,Separator) ---------------------------------------
|
|
%
|
|
% with
|
|
% Keyword one of SELECT, FROM, WHERE, or GROUP BY,
|
|
% ClauseCode the code corresponding to the appropriate clause of an SQL query, and
|
|
% Separator indicating the character(s) through which the items of a clause
|
|
% are separated from each other (',' or 'AND').
|
|
%
|
|
% --------------------------------------------------------------------------------------
|
|
|
|
% ILP
|
|
% print_clause(Keyword,[],_).
|
|
print_clause(_,[],_).
|
|
|
|
print_clause(Keyword,[Column|RestColumns],Separator):-
|
|
write(Keyword),
|
|
write(' '),
|
|
print_clause([Column|RestColumns],Separator).
|
|
|
|
print_clause(Keyword,Function,[Column],Separator):-
|
|
write(Keyword),
|
|
write(' '),
|
|
write(Function),
|
|
write('('),
|
|
print_clause([Column],Separator),
|
|
write(')').
|
|
|
|
|
|
|
|
|
|
|
|
% --- print_clause(ClauseCode,Separator) -----------------------------------------------
|
|
|
|
print_clause([Item],_):-
|
|
print_column(Item).
|
|
|
|
print_clause([Item,NextItem|RestItems],Separator):-
|
|
print_column(Item),
|
|
write(' '),
|
|
write(Separator),
|
|
write(' '),
|
|
print_clause([NextItem|RestItems],Separator).
|
|
|
|
|
|
|
|
|
|
% --- print_column(ColumnCode) --------------------------------
|
|
|
|
print_column('*'):-
|
|
write('*').
|
|
|
|
print_column(att(RangeVar,Attribute)):-
|
|
write(RangeVar),
|
|
write('.'),
|
|
write(Attribute).
|
|
|
|
print_column(rel(Relation,RangeVar)):-
|
|
write(Relation),
|
|
write(' '),
|
|
write(RangeVar).
|
|
|
|
print_column('$const$'(String)):-
|
|
get_type('$const$'(String),string),
|
|
write('"'),
|
|
write(String),
|
|
write('"').
|
|
|
|
print_column('$const$'(Number)):-
|
|
get_type('$const$'(Number),NumType),
|
|
type_compatible(NumType,number),
|
|
write(Number).
|
|
|
|
print_column(comp(LeftArg,Operator,RightArg)):-
|
|
print_column(LeftArg),
|
|
write(' '),
|
|
write(Operator),
|
|
write(' '),
|
|
print_column(RightArg).
|
|
|
|
print_column(LeftExpr * RightExpr):-
|
|
print_column(LeftExpr),
|
|
write('*'),
|
|
print_column(RightExpr).
|
|
|
|
print_column(LeftExpr / RightExpr):-
|
|
print_column(LeftExpr),
|
|
write('/'),
|
|
print_column(RightExpr).
|
|
|
|
print_column(LeftExpr + RightExpr):-
|
|
print_column(LeftExpr),
|
|
write('+'),
|
|
print_column(RightExpr).
|
|
|
|
print_column(LeftExpr - RightExpr):-
|
|
print_column(LeftExpr),
|
|
write('-'),
|
|
print_column(RightExpr).
|
|
|
|
print_column(agg_query(Function,Select,From,Where,Group)):-
|
|
nl,
|
|
write('('),
|
|
print_query(agg_query(Function,Select,From,Where,Group)),
|
|
write(')').
|
|
|
|
print_column(negated_existential_subquery(Select,From,Where)):-
|
|
print_query(negated_existential_subquery(Select,From,Where)).
|
|
|
|
print_column(existential_subquery(Select,From,Where)):-
|
|
print_query(existential_subquery(Select,From,Where)).
|
|
|
|
|
|
|
|
|
|
|
|
% --- queries_atom(Queries,QueryAtom) ----------------------------
|
|
%
|
|
% queries_atom(Queries,QueryAtom) returns in its second argument
|
|
% the SQL query as a Prolog atom. For efficiency reasons, a list
|
|
% of ASCII codes is ceated as a difference list, and it is then
|
|
% transformed to an atom by name/2
|
|
% ----------------------------------------------------------------
|
|
|
|
#ifdef MYDDAS_STATS
|
|
queries_atom(Queries,QueryAtom):-
|
|
c_db_stats_walltime(Start),
|
|
queries_atom_(Queries,QueryAtom),
|
|
c_db_stats_walltime(End),
|
|
c_db_stats_translate(Start,End).
|
|
|
|
queries_atom_(Queries,QueryAtom):-
|
|
#else
|
|
queries_atom(Queries,QueryAtom):-
|
|
#endif
|
|
|
|
queries_atom(Queries,QueryList,[]),
|
|
name(QueryAtom,QueryList).
|
|
|
|
|
|
|
|
queries_atom([Query],QueryList,Diff):-
|
|
query_atom(Query,QueryList,Diff).
|
|
|
|
queries_atom([Query|Queries],QueryList,Diff):-
|
|
Queries \= [],
|
|
query_atom(Query,QueryList,X1),
|
|
column_atom('UNION ',X1,X2),
|
|
queries_atom(Queries,X2,Diff).
|
|
|
|
|
|
|
|
% --- query_atom(QueryCode) --------------------------------
|
|
|
|
query_atom(query([agg_query(Function,Select,From,Where,Group)],_,_),QueryList,Diff):-
|
|
% --- ugly rule here: aggregate function only in SELECT Part of query ----
|
|
!,
|
|
query_atom(agg_query(Function,Select,From,Where,Group),QueryList,Diff).
|
|
|
|
query_atom(query(Select,From,Where),QueryList,Diff):-
|
|
clause_atom('SELECT',Select,',',QueryList,X1),
|
|
clause_atom('FROM',From,',',X1,X2),
|
|
clause_atom('WHERE',Where,'AND',X2,Diff).
|
|
|
|
query_atom(agg_query(Function,Select,From,Where,Group),QueryList,Diff):-
|
|
clause_atom('SELECT',Function,Select,',',QueryList,X1),
|
|
clause_atom('FROM',From,',',X1,X2),
|
|
clause_atom('WHERE',Where,'AND',X2,X3),
|
|
%ILP : PARA NAO POR OS GROUP BYS. FAZER FLAG PARA ISTO
|
|
clause_atom('GROUP BY',Group,',',X3,Diff).
|
|
|
|
|
|
query_atom(negated_existential_subquery(Select,From,Where),QueryList,Diff):-
|
|
column_atom('NOT EXISTS(',QueryList,X1),
|
|
clause_atom('SELECT',Select,',',X1,X2),
|
|
clause_atom('FROM',From,',',X2,X3),
|
|
clause_atom('WHERE',Where,'AND',X3,X4),
|
|
column_atom(')',X4,Diff).
|
|
|
|
query_atom(existential_subquery(Select,From,Where),QueryList,Diff):-
|
|
column_atom('EXISTS(',QueryList,X1),
|
|
clause_atom('SELECT',Select,',',X1,X2),
|
|
clause_atom('FROM',From,',',X2,X3),
|
|
clause_atom('WHERE',Where,'AND',X3,X4),
|
|
column_atom('LIMIT 1)',X4,Diff).
|
|
|
|
|
|
|
|
|
|
% --- clause_atom(Keyword,ClauseCode,Junctor,CurrAtom,QueryAtom) -------------
|
|
%
|
|
% with
|
|
% Keyword one of SELECT, FROM, WHERE, or GROUP BY,
|
|
% ClauseCode the code corresponding to the appropriate clause of an SQL query, and
|
|
% Junctor indicating the character(s) through which the items of a clause
|
|
% are separated from each other (',' or 'AND').
|
|
|
|
% ILP
|
|
% clause_atom(Keyword,[],_,QueryList,QueryList).
|
|
clause_atom(_,[],_,QueryList,QueryList).
|
|
% case there is no WHERE condition
|
|
clause_atom(_,[once],_,QueryList,Diff):-!,
|
|
column_atom(' ',QueryList,X1),
|
|
column_atom('LIMIT 1',X1,X2),
|
|
column_atom(' ',X2,Diff).
|
|
clause_atom(Keyword,[Column|RestColumns],Junctor,QueryList,Diff):-
|
|
column_atom(Keyword,QueryList,X1),
|
|
column_atom(' ',X1,X2),
|
|
clause_atom([Column|RestColumns],Junctor,X2,X3),
|
|
column_atom(' ',X3,Diff).
|
|
|
|
%DISTINCT
|
|
clause_atom(Keyword,'COUNTDISTINCT',[Column],Junctor,QueryList,Diff):-!,
|
|
column_atom(Keyword,QueryList,X1),
|
|
column_atom(' ',X1,X2),
|
|
column_atom('COUNT',X2,X3),
|
|
column_atom('(DISTINCT ',X3,X4),
|
|
clause_atom([Column],Junctor,X4,X5),
|
|
column_atom(') ',X5,Diff).
|
|
|
|
clause_atom(Keyword,Function,[Column],Junctor,QueryList,Diff):-
|
|
column_atom(Keyword,QueryList,X1),
|
|
column_atom(' ',X1,X2),
|
|
column_atom(Function,X2,X3),
|
|
column_atom('(',X3,X4),
|
|
clause_atom([Column],Junctor,X4,X5),
|
|
column_atom(') ',X5,Diff).
|
|
|
|
|
|
|
|
|
|
|
|
|
|
% --- clause_atom(ClauseCode,Junctor) --------------------------------
|
|
|
|
clause_atom([once],_,QueryList,Diff):-!,
|
|
column_atom(' LIMIT 1 ',QueryList,Diff).
|
|
|
|
clause_atom([Item],_,QueryList,Diff):-
|
|
column_atom(Item,QueryList,Diff).
|
|
|
|
clause_atom([Item,NextItem|RestItems],Junctor,QueryList,Diff):-
|
|
column_atom(Item,QueryList,X1),
|
|
column_atom(' ',X1,X2),
|
|
( NextItem = once ->
|
|
X4 = X2
|
|
;
|
|
column_atom(Junctor,X2,X3),
|
|
column_atom(' ',X3,X4)
|
|
),
|
|
clause_atom([NextItem|RestItems],Junctor,X4,Diff).
|
|
|
|
|
|
|
|
column_atom(att(RangeVar,Attribute),QueryList,Diff):-
|
|
column_atom(RangeVar,QueryList,X1),
|
|
column_atom('.',X1,X2),
|
|
column_atom(Attribute,X2,Diff).
|
|
|
|
column_atom(rel(Relation,RangeVar),QueryList,Diff):-
|
|
column_atom('',QueryList,X0),
|
|
column_atom(Relation,X0,X1),
|
|
column_atom(' ',X1,X2),
|
|
column_atom(RangeVar,X2,Diff).
|
|
|
|
column_atom('$const$'(String),QueryList,Diff):-
|
|
get_type('$const$'(String),string),
|
|
column_atom('"',QueryList,X1),
|
|
column_atom(String,X1,X2),
|
|
column_atom('"',X2,Diff).
|
|
|
|
column_atom('$const$'(Number),QueryList,Diff):-
|
|
get_type('$const$'(Number),NumType),
|
|
type_compatible(NumType,number),
|
|
column_atom(Number,QueryList,Diff).
|
|
|
|
column_atom(comp(LeftArg,Operator,RightArg),QueryList,Diff):-
|
|
column_atom(LeftArg,QueryList,X1),
|
|
column_atom(' ',X1,X2),
|
|
column_atom(Operator,X2,X3),
|
|
column_atom(' ',X3,X4),
|
|
column_atom(RightArg,X4,Diff).
|
|
|
|
column_atom(LeftExpr * RightExpr,QueryList,Diff):-
|
|
column_atom(LeftExpr,QueryList,X1),
|
|
column_atom('*',X1,X2),
|
|
column_atom(RightExpr,X2,Diff).
|
|
|
|
column_atom(LeftExpr + RightExpr,QueryList,Diff):-
|
|
column_atom(LeftExpr,QueryList,X1),
|
|
column_atom('+',X1,X2),
|
|
column_atom(RightExpr,X2,Diff).
|
|
|
|
column_atom(LeftExpr - RightExpr,QueryList,Diff):-
|
|
column_atom(LeftExpr,QueryList,X1),
|
|
column_atom('-',X1,X2),
|
|
column_atom(RightExpr,X2,Diff).
|
|
|
|
column_atom(LeftExpr / RightExpr,QueryList,Diff):-
|
|
column_atom(LeftExpr,QueryList,X1),
|
|
column_atom('/',X1,X2),
|
|
column_atom(RightExpr,X2,Diff).
|
|
|
|
column_atom(agg_query(Function,Select,From,Where,Group),QueryList,Diff):-
|
|
column_atom('(',QueryList,X1),
|
|
query_atom(agg_query(Function,Select,From,Where,Group),X1,X2),
|
|
column_atom(')',X2,Diff).
|
|
|
|
column_atom(negated_existential_subquery(Select,From,Where),QueryList,Diff):-
|
|
query_atom(negated_existential_subquery(Select,From,Where),QueryList,Diff).
|
|
|
|
column_atom(existential_subquery(Select,From,Where),QueryList,Diff):-
|
|
query_atom(existential_subquery(Select,From,Where),QueryList,Diff).
|
|
|
|
|
|
column_atom(Atom,List,Diff):-
|
|
atom(Atom),
|
|
name(Atom,X1),
|
|
append(X1,Diff,List).
|
|
|
|
column_atom(Number,List,Diff) :-
|
|
number(Number),
|
|
name(Number,X1),
|
|
append(X1,Diff,List).
|
|
|
|
|
|
|
|
% --- gensym(Root,Symbol) ----------------------------------------------------
|
|
%
|
|
% SEPIA 3.2. version - other Prolog implementations provide gensym/2
|
|
% and init_gensym/1 as built-ins. */
|
|
%
|
|
% (C) Christoph Draxler, Aug. 1992
|
|
%
|
|
%
|
|
|
|
init_gensym(Atom) :-
|
|
set_value(Atom,'@').
|
|
|
|
gensym(Atom,Var) :-
|
|
var(Var),
|
|
get_value(Atom,Value),
|
|
char_code(Value,Code),
|
|
NewCode is Code + 1,
|
|
char_code(Var,NewCode),
|
|
set_value(Atom,Var).
|
|
|
|
|
|
|
|
% --- auxiliary predicates (some of them may be built-in... --------------------
|
|
|
|
repeat_n(N):-
|
|
integer(N),
|
|
N > 0,
|
|
repeat_1(N).
|
|
|
|
repeat_1(1):-!.
|
|
repeat_1(_).
|
|
repeat_1(N):-
|
|
N1 is N-1,
|
|
repeat_1(N1).
|
|
|
|
|
|
|
|
% --- set_difference(SetA,SetB,Difference) --------------------------------------------
|
|
%
|
|
% SetA - SetB = Difference
|
|
|
|
set_difference([],_,[]).
|
|
|
|
set_difference([Element|RestSet],Set,[Element|RestDifference]):-
|
|
not member(Element,Set),
|
|
set_difference(RestSet,Set,RestDifference).
|
|
|
|
set_difference([Element|RestSet],Set,RestDifference):-
|
|
member(Element,Set),
|
|
set_difference(RestSet,Set,RestDifference).
|
|
|
|
|
|
% --- Mapping of Prolog operators to SQL operators -------------------------------------
|
|
|
|
comparison(=,=).
|
|
comparison(<,<).
|
|
comparison(=<,'<=').
|
|
comparison(>=,'>=').
|
|
comparison(>,>).
|
|
comparison(@<,<).
|
|
comparison(@>,>).
|
|
|
|
|
|
negated_comparison(=,'<>').
|
|
negated_comparison(\=,=).
|
|
negated_comparison(>,'<=').
|
|
negated_comparison(=<,>).
|
|
negated_comparison(<,>=).
|
|
negated_comparison(>=,<).
|
|
|
|
|
|
% --- aggregate_function(PrologFunctor,SQLFunction) -----------------
|
|
|
|
aggregate_functor(avg,'AVG').
|
|
aggregate_functor(min,'MIN').
|
|
aggregate_functor(max,'MAX').
|
|
aggregate_functor(sum,'SUM').
|
|
aggregate_functor(count,'COUNT').
|
|
aggregate_functor(countdistinct,'COUNTDISTINCT').
|
|
|
|
|
|
|
|
% --- type system --------------------------------------------------------------
|
|
%
|
|
% A rudimentary type system is provided for consistency checking during the
|
|
% translation and for output formatting
|
|
%
|
|
% The basic types are string and number. number has the subtypes integer and
|
|
% real.
|
|
%
|
|
% ------------------------------------------------------------------------------
|
|
|
|
|
|
type_compatible(Type,Type):-
|
|
is_type(Type).
|
|
type_compatible(SubType,Type):-
|
|
subtype(SubType,Type).
|
|
type_compatible(Type,SubType):-
|
|
subtype(SubType,Type).
|
|
|
|
|
|
% --- subtype(SubType,SuperType) -----------------------------------------------
|
|
%
|
|
% Simple type hierarchy checking
|
|
%
|
|
% ------------------------------------------------------------------------------
|
|
|
|
subtype(SubType,SuperType):-
|
|
is_subtype(SubType,SuperType).
|
|
|
|
subtype(SubType,SuperType):-
|
|
is_subtype(SubType,InterType),
|
|
subtype(InterType,SuperType).
|
|
|
|
|
|
|
|
% --- is_type(Type) ------------------------------------------------------------
|
|
%
|
|
% Type names
|
|
%
|
|
% ------------------------------------------------------------------------------
|
|
|
|
is_type(number).
|
|
is_type(integer).
|
|
is_type(real).
|
|
is_type(string).
|
|
is_type(natural).
|
|
|
|
|
|
% --- is_subtype(SubType,SuperType) --------------------------------------------
|
|
%
|
|
% Simple type hierarchy for numeric types
|
|
%
|
|
% ------------------------------------------------------------------------------
|
|
|
|
is_subtype(integer,number).
|
|
is_subtype(real,number).
|
|
is_subtype(natural,integer).
|
|
|
|
|
|
% --- get_type(Constant,Type) --------------------------------------------------
|
|
%
|
|
% Prolog implementation specific definition of type retrieval
|
|
% sepia Prolog version given here
|
|
%
|
|
% ------------------------------------------------------------------------------
|
|
|
|
get_type('$const$'(Constant),integer):-
|
|
integer(Constant),!.
|
|
|
|
get_type('$const$'(Constant),real):-
|
|
number(Constant),!.
|
|
|
|
get_type('$const$'(Constant),string):-
|
|
atom(Constant).
|
|
|
|
|