ComparisonEngine.h

#ifndef _ENGINE
#define _ENGINE

#include "Comparison.h"
#include "ComparisonEngine.h"
#include "File.h"
#include "Record.h"
#include "Schema.h"

class Record;
class Comparison;
class OrderMaker;
class CNF;

class ComparisonEngine {
   private:
    int Run(Record *left, Record *literal, Comparison *c);
    int Run(Record *left, Record *right, Record *literal, Comparison *c);

   public:
    // this version of Compare is for sorting.  The OrderMaker struct
    // encapsulates the specification for a sort order.  For example,
    // say you are joining two tables on R.att1 = S.att2, and so
    // you want to sort R using att1.  The OrderMaker struct specifies
    // this sort ordering on att1.  Compare returns a negative number,
    // a 0, or a positive number if left is less than, equal to, or
    // greater than right.   This particular version of Compare is used
    // when both of the records come from the SAME RELATION
    int Compare(Record *left, Record *right, OrderMaker *orderUs);

    // similar to the last function, except that this one works in the
    // case where the two records come from different input relations
    // it is used to do sorts for a sort-merge join
    int Compare(Record *left, OrderMaker *order_left, Record *right, OrderMaker *order_right);

    // this applies the given CNF to the three records and either
    // accepts the records or rejects them.
    // It is is for binary operations such as join.  Returns
    // a 0 if the given CNF evaluates to false over the record pair
    int Compare(Record *left, Record *right, Record *literal, CNF *myComparison);

    // like the last one, but for unary operations
    int Compare(Record *left, Record *literal, CNF *myComparison);

    int CompareLit(Record *left, Record *literal, OrderMaker *orderUs);
};

#endif