Evaluator


1   /*
2   // $Id: //open/mondrian/src/main/mondrian/olap/Evaluator.java#24 $
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) 2001-2002 Kana Software, Inc.
7   // Copyright (C) 2001-2007 Julian Hyde and others
8   // All Rights Reserved.
9   // You must accept the terms of that agreement to use this software.
10  //
11  // jhyde, 27 July, 2001
12  */
13  
14  package mondrian.olap;
15  
16  import mondrian.calc.ParameterSlot;
17  import java.util.List  ;
18  import java.util.Locale  ;
19  
20  /**
21   * An <code>Evaluator</code> holds the context necessary to evaluate an
22   * expression.
23   *
24   * @author jhyde
25   * @since 27 July, 2001
26   * @version $Id: //open/mondrian/src/main/mondrian/olap/Evaluator.java#24 $
27   */
28  public interface Evaluator {
29  
30      /**
31       * Returns the current cube.
32       */
33      Cube getCube();
34  
35      /**
36       * Returns the current query.
37       */
38      Query getQuery();
39  
40      /**
41       * Creates a new evaluator with each given member overriding the state of
42       * the current validator for its dimension. Other dimensions retain the
43       * same state as this validator.
44       */
45      Evaluator push(Member[] members);
46  
47      /**
48       * Creates a new evaluator with the same state.
49       * Equivalent to {@link #push(Member[]) push(new Member[0])}.
50       */
51      Evaluator push();
52  
53      /**
54       * Creates a new evaluator with the same state except for one member.
55       * Equivalent to
56       * {@link #push(Member[]) push(new Member[] &#124;member&#125;)}.
57       */
58      Evaluator push(Member member);
59  
60      /**
61       * Restores previous evaluator.
62       */
63      Evaluator pop();
64  
65      /**
66       * Makes <code>member</code> the current member of its dimension. Returns
67       * the previous context.
68       *
69       * @pre member != null
70       * @post return != null
71       */
72      Member setContext(Member member);
73  
74      void setContext(List  <Member> memberList);
75  
76      void setContext(Member[] members);
77  
78      Member getContext(Dimension dimension);
79  
80      /**
81       * Calculates and returns the value of the cell at the current context.
82       */
83      Object   evaluateCurrent();
84  
85      /**
86       * Returns the format string for this cell. This is computed by evaluating
87       * the format expression in the current context, and therefore different
88       * cells may have different format strings.
89       */
90      public String   getFormatString();
91  
92      /**
93       * Formats a value as a string according to the current context's
94       * format.
95       */
96      String   format(Object   o);
97  
98      /**
99       * Formats a value as a string according to the current context's
100      * format, using a given format string.
101      */
102     String   format(Object   o, String   formatString);
103 
104     /**
105      * Returns number of ancestor evaluators. Used to check for infinite
106      * loops.
107      *
108      * @post return getParent() == null ? 0 : getParent().getDepth() + 1
109      */
110     int getDepth();
111 
112     /**
113      * Returns parent evaluator.
114      */
115     Evaluator getParent();
116 
117     /**
118      * Returns the connection's locale.
119      */
120     Locale   getConnectionLocale();
121 
122     /**
123      * Retrieves the value of property <code>name</code>. If more than one
124      * member in the current context defines that property, the one with the
125      * highest solve order has precedence.
126      *
127      * <p>If the property is not defined, default value is returned.
128      */
129     Object   getProperty(String   name, Object   defaultValue);
130 
131     /**
132      * Returns a {@link SchemaReader} appropriate for the current
133      * access-control context.
134      */
135     SchemaReader getSchemaReader();
136 
137     /**
138      * Simple caching of the result of an <code>Exp</code>. The
139      * key for the cache consists of all members of the current
140      * context that <code>exp</code> depends on. Members of
141      * independent dimensions are not part of the key.
142      *
143      * @see mondrian.calc.Calc#dependsOn
144      */
145     Object   getCachedResult(ExpCacheDescriptor key);
146 
147     /**
148      * Returns true for an axis that is NON EMPTY.
149      *
150      * <p>May be used by expression
151      * evaluators to optimize their result. For example, a top-level crossjoin
152      * may be optimized by removing all non-empty set elements before
153      * performing the crossjoin. This is possible because of the identity
154      *
155      * <blockquote><code>nonempty(crossjoin(a, b)) ==
156      * nonempty(crossjoin(nonempty(a), nonempty(b));</code></blockquote>
157      */
158     boolean isNonEmpty();
159 
160     /**
161      * Sets whether an expression evaluation should filter out empty cells.
162      * Allows expressions to modify non empty flag to evaluate their children.
163      */
164     void setNonEmpty(boolean nonEmpty);
165 
166     /**
167      * Creates an exception which indicates that an error has occurred during
168      * the runtime evaluation of a function. The caller should then throw that
169      * exception.
170      */
171     RuntimeException   newEvalException(Object   context, String   s);
172 
173     /**
174      * Evaluates a named set.
175      */
176     Object   evaluateNamedSet(String   name, Exp exp);
177 
178     /**
179      * Returns an array of the members which make up the current context.
180      */
181     Member[] getMembers();
182 
183     /**
184      * Returns the number of times that this evaluator has told a lie when
185      * retrieving cell values.
186      */
187     int getMissCount();
188 
189     /**
190      * Returns the value of a parameter, evaluating its default value if it is
191      * not set.
192      */
193     Object   getParameterValue(ParameterSlot slot);
194 
195     /**
196      * @return the iteration length of the current context
197      */
198     int getIterationLength();
199 
200     /**
201      * Sets the iteration length for the current evaluator context
202      *
203      * @param length length to be set
204      */
205     void setIterationLength(int length);
206 
207     /**
208      * @return true if evaluating axes
209      */
210     boolean isEvalAxes();
211 
212     /**
213      * Indicate whether the evaluator is evaluating the axes
214      *
215      * @param evalAxes true if evaluating axes
216      */
217     void setEvalAxes(boolean evalAxes);
218 }
219 
220 // End Evaluator.java
221
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