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duboissim
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solution.pl
68
solution.pl
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@ -2,6 +2,25 @@
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* Authors:
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* Dubois Brieuc
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* Dubois Simon
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*
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* Known Limitation and problems:
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* Currently a condtion in a query as to contain no space in order to function properly
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* Ex: the condtion +name="Dakota" will work but the conditions +name = "Dakota"
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* or +name="North Dakota" will not. This is due to the way we parse the query. We did it
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* with split_string. We were not able to use the prolog_term predicate given to us.
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*
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* SQL test:
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* Test 10 failed because instead of returning [+<atom>, +<atom>] for the column name
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* we return [<atom>, <atom>] because that's how we store the column names after an insert
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*
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* Test 12 and 21:
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* When we return row of an empty table instead of having [] we have [_] same thing happens after
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* we drop a table.
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*
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* DCG test:
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* Test 5 failed:
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* We don't cover the case where the number of values inserted isn't the same as the number of columns
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* in the table.
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*/
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:- dynamic tables/0.
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@ -159,7 +178,9 @@ delete(_, _).
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does_match([], _, _) :- !.
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/**
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* fails if conditons isn't respected in row
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*/
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does_match([Cond|Rest], Table, Row) :-
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% Extract the operator, field and value from the condition
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Cond =.. [Operator | T],
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@ -222,13 +243,17 @@ selec(Table, _, _, _) :-
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!.
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selec(Table, Selector, Cond, Projection) :-
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%fetch columns names and all rows of Table
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tabl(Table, Cols),
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row(Table, R),
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%remove rows that don't respect the conditions
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does_match(Cond, Table, R),
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%reduce result to only selected columns
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selector(R,Cols, Selector, [],[],ColumnNames,ColumnValue),
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%reorder result to match query order
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reverse(ColumnNames, Names),
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reverse(ColumnValue, Values),
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%unify the lists to projection
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Projection = Names/Values.
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selec(Table, *, Cond, Projection) :-
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@ -238,17 +263,18 @@ selec(Table, *, Cond, Projection) :-
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Projection = Cols/R.
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/**
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* Row: A row from the table
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* Cols: name of the column of the table
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* [Selector|Selectors] name(s) of the column(s) for selection
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* AccCols: acumulator list for the column(s) name(s)
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* AccVals: acumulator list for the row(s) values
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* ColumnNames: List returning the column(s) name(s)
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* ColumnValue: List returning the row values for each column
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* +Row: A row from the table
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* +Cols: name of the column of the table
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* +[Selector|Selectors] name(s) of the column(s) for selection
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* +AccCols: acumulator list for the column(s) name(s)
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* +AccVals: acumulator list for the row(s) values
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* -ColumnNames: List returning the column(s) name(s)
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* -ColumnValue: List returning the row values for each column
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*
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* This predicate return
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*/
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%base case
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selector(_,_,[],ColumnNames, ColumnValue, ColumnNames, ColumnValue):-!.
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selector(Row, Cols, [+Selector|Selectors], AccCols, AccVals, ColumnNames, ColumnValue):-
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@ -256,7 +282,7 @@ selector(Row, Cols, [+Selector|Selectors], AccCols, AccVals, ColumnNames, Column
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%find the value corresponding to the column in the row
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nth0(Index, Cols, Selector),
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nth0(Index, Row, Value),
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%go to next column tho evaluate
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%go to next column tho evaluate and store value and corresponging name
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selector(Row, Cols, Selectors, [Selector|AccCols], [Value|AccVals], ColumnNames, ColumnValue)
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;
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string_concat(Selector, " isn't a column of table ", Error),
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@ -299,9 +325,7 @@ ble names are atoms, while column names should follow the format out-
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lined before (+<atom>). <cond>denotes a Prolog goal, in Prolog syntax
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— following the same format as the possible values of items of the Conds
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list passed to selec and delete.
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<value>denotes a prolog value that can be stored into a row. You do
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not need to handle parsing Prolog (<cond>and <value>) by yourself,
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we’ll show how to do it below.
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<value>denotes a prolog value that can be stored into a row.
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The semantics of this predicate is that of the SQL-predicate contained in
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the Query string.
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A “SELECT” query maps to the selec predicate, while an “INSERT”
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@ -333,24 +357,32 @@ query(Query, Result):-
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apply(Fun, Args),
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last(Args, Result).
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/**
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* For all parse_query on Query must be initiated
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*/
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/**
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* Parse SELECT * FROM <table> WHERE <conds>
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*/
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parse_query(Query, selec, [AtomTable, *, AtomsConds, R]):-
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%split the query
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split_string(Query, " ", ",;+", SplitQuery),
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append(["SELECT"], L1, SplitQuery),
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append(["*"], ["FROM"|L2], L1),
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append([Table], ["WHERE"|Conds],L2),
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%cast into correct type
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atom_string(AtomTable, Table),
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maplist(parse_cond, AtomsConds, Conds),!.
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/**
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* Parse SELECT <cols> FROM <table> WHERE <conds>
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*/
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parse_query(Query, selec, [AtomTable, AtomsSelectors, AtomsConds, R]):-
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%split the query
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split_string(Query, " ", ",;+", SplitQuery),
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append(["SELECT"], L1, SplitQuery),
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append(Selectors, ["FROM"|L2], L1),
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append([Table], ["WHERE"|Conds],L2),
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%cast into correct type
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atom_string(AtomTable, Table),
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maplist(atom_string, AtomsSelectors1, Selectors),
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maplist(add_plus, AtomsSelectors, AtomsSelectors1),
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@ -360,9 +392,11 @@ parse_query(Query, selec, [AtomTable, AtomsSelectors, AtomsConds, R]):-
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* Parse SELECT * FROM <table>
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*/
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parse_query(Query, selec, [AtomTable, *, R]):-
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%split the query
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split_string(Query, " ", ",;+", SplitQuery),
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append(["SELECT"], L1, SplitQuery),
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append(["*"], ["FROM",Table], L1),
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%cast into correct type
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atom_string(AtomTable, Table),
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maplist(parse_cond, AtomsConds, Conds),!.
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@ -370,23 +404,31 @@ parse_query(Query, selec, [AtomTable, *, R]):-
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* Parse SELECT <cols> FROM <table>
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*/
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parse_query(Query, selec, [AtomTable, AtomsSelectors, R]):-
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%split the query
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split_string(Query, " ", ",;+", SplitQuery),
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append(["SELECT"], L1, SplitQuery),
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append(Selectors, ["FROM",Table], L1),
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%cast into correct type
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atom_string(AtomTable, Table),
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maplist(atom_string, AtomsSelectors1, Selectors),
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maplist(add_plus, AtomsSelectors, AtomsSelectors1).
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parse_query(Query, insert, [AtomTable, Values]):-
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%split the query
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split_string(Query, " ", '",();', SplitQuery),
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append(["INSERT", "INTO"], L1, SplitQuery),
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L1 = [Table | L2],
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append(_, ["VALUES"|Values1], L2),
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%cast into correct type
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maplist(is_number, Values, Values1),
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atom_string(AtomTable, Table).
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add_plus(+A, A).
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/**
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* For all parse_cond only Cond must be initiated
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*/
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% parse >= conditon
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parse_cond(+AtomLeft>=AtomRight, Cond):-
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string_chars(Cond, Code),
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