include/Predicate.h

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  13  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
  14  *   GNU General Public License for more details.                          *
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  17 #ifndef PREDICATE_H
  18 #define PREDICATE_H
  19 #include<DataType.h>
  20 class PredicateImpl;
  21 class Predicate;
  22 /**
  23 * @class Condition
  24 *
  25 * @brief Represents the condition part of SQL Query.
  26 * Used in SELECT, UPDATE and DELETE statement to retrieve only tuples which satisfy<br/>
  27 * the condition. This represents the root of the logical expression. This logical <br/>
  28 * expression may contain multiple terms(predicates).<br/>
  29 * For example to set this condition f1 == f2 && f1 == 100. <br/>
  30 *    Condition c1;<br/>
  31 *    int val1 = 100;<br/>
  32 *    c1.setTerm("f1", OpEquals, &val1);<br/>
  33 *    Predicate *p1 = c1.getPredicate();<br/>
  34 *    Condition c2;<br/>
  35 *    c2.setTerm("f1", opEquals, "f2");<br/>
  36 *    Predicate *p2 = c2.getPredicate();<br/>
  37 *    Condtion rootCondition;<br/>
  38 *    rootCondition.setTerm(p1, OpAnd, p2);<br/>
  39 *    table->setCondition(rootCondition);<br/>
  40 *
  41 */
  42 class Condition
  43 {
  44     Predicate *pred;
  45     public:
  46     Condition();
  47     ~Condition();
  48     void reset();
  49
  50     /** gets the current predicate. This is used to create logical expressions with terms or predicates.
  51     *   @return Predicate* predicate
  52     */
  53     Predicate* getPredicate() { return pred; }
  54
  55     /** sets the current predicate. This is set after creating the logical expression and used in the table interface for setting the condition.
  56     *   @param Predicate* predicate
  57     */
  58     void setPredicate(Predicate * predicate) {  pred = predicate; }
  59
  60
  61     /** sets the predicate term of form f1 = f2.
  62     *   @param fName1* field name
  63     *   @param op comparision operator
  64     *   @param fName2* field name
  65     */
  66     void setTerm(const char* fName1, ComparisionOp op, const char *fName2);
  67
  68     /** sets the predicate term of form f1 = 10
  69     *   @param fName1* field name
  70     *   @param op comparision operator(=,!=, >,<,>=,<=)
  71     *   @param opnd* pointer to the  value
  72     */
  73     void setTerm(const char* fName1, ComparisionOp op, void *opnd);
  74
  75     /** sets the predicate term of form f1 =10, using pointer semantics
  76     *   @param fName1* field name
  77     *   @param op comparision operator(=,!=, >,<,>=,<=)
  78     *   @param opnd** pointer to pointer to the  value
  79     */
  80     void setTerm(const char* fName1, ComparisionOp op, void **opnd);
  81
  82
  83     /** sets the predicate term of form f1 = f2 && f1 = 100.
  84     *   @param p1* predicate
  85     *   @param op logical operator (&&, ||, !)
  86     *   @param p2* predicate
  87     */
  88     void setTerm(Predicate *p1, LogicalOp op, Predicate *p2 = NULL);
  89
  90 };
  91
  92 /**
  93 * @class Predicate
  94 *
  95 * @brief Represents a single term in the condition.
  96 * Condition is logical expression composed of terms and logical operators. This
  97 * represents the leaf of the logical expression tree. This is designed using composite
  98 * design pattern
  99 *
 100 *
 101 */
 102 class Predicate
 103 {
 104     public:
 105     virtual void setTerm(const char* fName1, ComparisionOp op, const char *fName2)=0;
 106
 107     //Operand should be of the same type of the field. This is must
 108     virtual void setTerm(const char* fName1, ComparisionOp op, void *opnd)=0;
 109
 110     //Operand should be of the same type of the field. This is must
 111     virtual void setTerm(const char* fName1, ComparisionOp op, void **opnd)=0;
 112
 113     virtual void setTerm(Predicate *p1, LogicalOp op, Predicate *p2 = NULL)=0;
 114
 115     virtual void print()=0;
 116     virtual ~Predicate(){}
 117 };
 118
 119
 120 #endif