StarPredicate


1   /*
2   // $Id: //open/mondrian/src/main/mondrian/rolap/StarPredicate.java#1 $
3   // This software is subject to the terms of the Common Public License
4   // Agreement, available at the following URL:
5   // http://www.opensource.org/licenses/cpl.html.
6   // Copyright (C) 2007-2007 Julian Hyde
7   // All Rights Reserved.
8   // You must accept the terms of that agreement to use this software.
9   */
10  package mondrian.rolap;
11  
12  import java.util.List  ;
13  
14  /**
15   * Condition which constrains a set of values of a single
16   * {@link mondrian.rolap.RolapStar.Column} or a set of columns.
17   *
18   * <p>For example, the predicate
19   * <code>Range([Time].[1997].[Q3], [Time].[1998].[Q2])</code>
20   * constrains the <code>year</code> and <code>quarter</code> columns:
21   *
22   * <blockquote><code>
23   * &nbsp;&nbsp;((year = 1997 and quarter >= 'Q3')<br/>
24   * &nbsp;&nbsp;&nbsp;&nbsp;or (year > 1997))<br/>
25   * and ((year = 1998 and quarter <= 'Q2')<br/>
26   * &nbsp;&nbsp;&nbsp;&nbsp;or (year < 1998))</code></blockquote>
27   *
28   * @author jhyde
29   * @version $Id: //open/mondrian/src/main/mondrian/rolap/StarPredicate.java#1 $
30   * @since Jan 15, 2007
31   */
32  public interface StarPredicate {
33      /**
34       * Returns a list of constrained columns.
35       *
36       * @return List of constrained columns
37       */
38      public List  <RolapStar.Column> getConstrainedColumnList();
39  
40      /**
41       * Appends a description of this predicate to a <code>StringBuilder</code>.
42       * For example:<ul>
43       * <li>=any</li>
44       * <li>=5</li>
45       * <li>in (2, 4, 6)</li>
46       * </ul>
47       *
48       * @param buf Builder to append to
49       */
50      public abstract void describe(StringBuilder   buf);
51  
52      /**
53       * Evaluates a constraint against a list of values.
54       *
55       * <p>If one of the values is {@link #WILDCARD}, returns true if constraint is
56       * true for all possible values of that column.
57       *
58       * @param valueList List of values, one for each constrained column
59       * @return Whether constraint holds for given set of values
60       */
61      public boolean evaluate(List  <Object  > valueList);
62  
63      /**
64       * Returns whether this Predicate has the same constraining effect as the
65       * other constraint. This is weaker than {@link #equals(Object)} -- it is
66       * possible for two different members to constrain the same column in the
67       * same way.
68       */
69      boolean equalConstraint(StarPredicate that);
70  
71      /**
72       * Returns the logical inverse of this Predicate. The result is a Predicate
73       * which holds whenever this predicate holds but the other does not.
74       *
75       * @pre predicate != null
76       */
77      StarPredicate minus(StarPredicate predicate);
78  
79      /**
80       * Wildcard value for {@link #evaluate(java.util.List)}.
81       */
82      Object   WILDCARD = new Object  ();
83  }
84  
85  // End StarPredicate.java
86
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