include/Predicate.h

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   2  *   Copyright (C) 2007 by www.databasecache.com                           *
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  11  *   This program is distributed in the hope that it will be useful,       *
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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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  16   ***************************************************************************/
  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 * @author Prabakaran Thirumalai
  41 */
  42 class Condition
  43 {
  44     Predicate *pred;
  45     public:
  46     Condition();
  47     ~Condition();
  48
  49     /** gets the current predicate. This is used to create logical expressions with terms or predicates.
  50     *   @return Predicate* predicate
  51     */
  52     Predicate* getPredicate() { return pred; }
  53     /** sets the predicate term of form f1 = f2.
  54     *   @param fName1* field name
  55     *   @param op comparision operator
  56     *   @param fName2* field name
  57     */
  58     void setTerm(const char* fName1, ComparisionOp op, const char *fName2);
  59
  60     /** sets the predicate term of form f1 = 10
  61     *   @param fName1* field name
  62     *   @param op comparision operator(=,!=, >,<,>=,<=)
  63     *   @param opnd* pointer to the  value
  64     */
  65     void setTerm(const char* fName1, ComparisionOp op, void *opnd);
  66
  67     /** sets the predicate term of form f1 = f2 && f1 = 100.
  68     *   @param p1* predicate
  69     *   @param op logical operator (&&, ||, !)
  70     *   @param p2* predicate
  71     */
  72     void setTerm(Predicate *p1, LogicalOp op, Predicate *p2 = NULL);
  73
  74 };
  75
  76 /**
  77 * @class Predicate
  78 *
  79 * @brief Represents a single term in the condition.
  80 * Condition is logical expression composed of terms and logical operators. This
  81 * represents the leaf of the logical expression tree. This is designed using composite
  82 * design pattern
  83 *
  84 * @author Prabakaran Thirumalai
  85 */
  86 class Predicate
  87 {
  88     public:
  89     virtual void setTerm(const char* fName1, ComparisionOp op, const char *fName2)=0;
  90
  91     //Operand should be of the same type of the field. This is must
  92     virtual void setTerm(const char* fName1, ComparisionOp op, void *opnd)=0;
  93
  94     virtual void setTerm(Predicate *p1, LogicalOp op, Predicate *p2 = NULL)=0;
  95     virtual ~Predicate(){}
  96 };
  97
  98
  99 #endif