ReverseIterator


1   package com.daffodilwoods.daffodildb.server.sql99.dql.iterator.table;
2   
3   import com.daffodilwoods.daffodildb.client.*;
4   import com.daffodilwoods.daffodildb.server.datasystem.utility._Record;
5   import com.daffodilwoods.daffodildb.server.sql99.common.*;
6   import com.daffodilwoods.daffodildb.server.sql99.dql.execution.*;
7   import com.daffodilwoods.daffodildb.server.sql99.dql.iterator.*;
8   import com.daffodilwoods.daffodildb.server.sql99.utils.*;
9   import com.daffodilwoods.daffodildb.utils.field.*;
10  import com.daffodilwoods.database.resource.*;
11  import com.daffodilwoods.database.sqlinitiator.*;
12  import com.daffodilwoods.database.utility.P;
13  
14  /**
15   *
16   * <p>Title: ReverseIterator </p>
17   * <p>Description: This Class is used to reverse the underlying iterator.
18   * This Class is responsible to return the records in the specified order.
19   * If a particular table has an index on a table on a particular column and the
20   * user wants to retrieve the records in descending order for that particular
21   * column, records are retrived from the table and records are returned in the
22   * reverse order to maintain the descending order requirement and optimised use
23   * of the index of that table.
24   *
25   * The navigation methods are implemented to reverse the effect of the call to
26   * the iterator and all the remaining methods transfer the call to the
27   * underlying iterator.
28   * </p>
29   * <p>Copyright: Copyright (c) 2004</p>
30   * <p>Company: </p>
31   * @author not attributable
32   * @version 1.0
33   */
34  public class ReverseIterator extends AbstractVariableValues implements _Iterator {
35  
36    /**
37     * Underlying iterator from which records to be retrived and to be returned
38     * in the reverse order.
39     */
40    _Iterator iterator;
41  
42    private _Reference[] underlyingRef;
43  
44    public ReverseIterator(_Iterator iterator) {
45      this.iterator = iterator;
46    }
47  
48    /**
49     * This method is used to get the first record of the iterator.
50     * This method returns the last record of the underling iterator to fulfill
51     * the order requirements of reverse iterator.
52     * @return true if record found, false otherwise.
53     * @throws com.daffodilwoods.database.resource.DException
54     */
55    public boolean first() throws com.daffodilwoods.database.resource.DException {
56      return iterator.last();
57    }
58  
59    /**
60     * This method is used to get the last record of the iterator.
61     * This method returns the first record of the underling iterator to fulfill
62     * the order requirements of reverse iterator.
63     * @return true if record found, false otherwise.
64     * @throws com.daffodilwoods.database.resource.DException
65     */
66    public boolean last() throws com.daffodilwoods.database.resource.DException {
67      return iterator.first();
68    }
69  
70    /**
71     * This method is used to get the next record of the iterator.
72     * This method returns the previos record of the underling iterator to fulfill
73     * the order requirements of reverse iterator.
74     * @return true if record found, false otherwise.
75     * @throws com.daffodilwoods.database.resource.DException
76     */
77    public boolean next() throws com.daffodilwoods.database.resource.DException {
78      return iterator.previous();
79    }
80  
81    /**
82     * This method is used to get the previous record of the iterator.
83     * This method returns the next record of the underling iterator to fulfill
84     * the order requirements of reverse iterator.
85     * @return true if record found, false otherwise.
86     * @throws com.daffodilwoods.database.resource.DException
87     */
88    public boolean previous() throws com.daffodilwoods.database.resource.DException {
89      return iterator.next();
90    }
91  
92    /**
93     * The following methods just transfer the call to the underlying iterator.
94     * There is no need to change the following methods for reverse order
95     * requirement, thus, these method just transfer call to underlying iterator.
96     */
97  
98    public _OrderCount getOrderCounts() throws com.daffodilwoods.database.resource.DException {
99      return iterator.getOrderCounts();
100   }
101 
102   public TableDetails[] getTableDetails() throws com.daffodilwoods.database.resource.DException {
103     return iterator.getTableDetails();
104   }
105 
106   public _Iterator getBaseIterator(ColumnDetails column) throws com.daffodilwoods.database.resource.DException {
107     return iterator.getBaseIterator(column);
108   }
109 
110   public void setKeyCount(Object  [][] parm1) throws com.daffodilwoods.database.resource.DException {
111      iterator.setKeyCount(parm1);
112   }
113 
114   public void setConditionVariableValue(_Reference[] parm1, Object  [] parm2, int parm3) throws com.daffodilwoods.database.resource.DException {
115     if(underlyingRef!=null){
116      parm1 = GeneralPurposeStaticClass.getJointReferences(parm1,underlyingRef);
117      parm2 = GeneralPurposeStaticClass.getJointValues(this, parm2,underlyingRef.length);
118    }
119     iterator.setConditionVariableValue(parm1, parm2 , parm3);
120   }
121 
122   public Object   getColumnValues() throws com.daffodilwoods.database.resource.DException {
123     return iterator.getColumnValues() ;
124   }
125 
126   public _KeyColumnInformation[] getKeyColumnInformations() throws com.daffodilwoods.database.resource.DException {
127     return iterator.getKeyColumnInformations();
128   }
129 
130   public Object  [] getUniqueColumnReference() throws com.daffodilwoods.database.resource.DException {
131     return iterator.getUniqueColumnReference();
132   }
133 
134   public boolean seek(Object   parm1) throws com.daffodilwoods.database.resource.DException {
135     return iterator.seek(parm1);
136   }
137 
138   public _Order getDefaultOrder() throws com.daffodilwoods.database.resource.DException {
139     return iterator.getDefaultOrder();
140   }
141 
142   public _ExecutionPlan getExecutionPlan() throws com.daffodilwoods.database.resource.DException {
143     return iterator.getExecutionPlan();
144   }
145 
146   public ExecutionPlanForBrowser getExecutionPlanForBrowser() throws com.daffodilwoods.database.resource.DException {
147     return iterator.getExecutionPlanForBrowser();
148   }
149 
150   public boolean seekFromTop(_IndexPredicate[] parm1) throws com.daffodilwoods.database.resource.DException {
151      return iterator.seekFromTop(parm1);
152   }
153 
154   public boolean seekFromTopRelative(Object   parm1) throws com.daffodilwoods.database.resource.DException {
155      return iterator.seekFromTopRelative(parm1);
156   }
157 
158   public boolean seekFromBottom(_IndexPredicate[] parm1) throws com.daffodilwoods.database.resource.DException {
159      return iterator.seekFromBottom(parm1);
160   }
161 
162   public boolean seekFromBottomRelative(Object   parm1) throws com.daffodilwoods.database.resource.DException {
163      return iterator.seekFromBottomRelative(parm1);
164   }
165 
166   public Object   getKey() throws com.daffodilwoods.database.resource.DException {
167     return iterator.getKey();
168   }
169 
170   public void move(Object   parm1) throws com.daffodilwoods.database.resource.DException {
171     iterator.move(parm1);
172   }
173 
174   public byte[] getByteKey() throws DException {
175    return iterator.getByteKey();
176  }
177 
178  public void moveByteKey(byte[] key) throws DException {
179    iterator.moveByteKey(key);
180  }
181 
182 
183   public Object   getColumnValues(int[] parm1) throws com.daffodilwoods.database.resource.DException {
184      return iterator.getColumnValues(parm1);
185   }
186 
187   public _Record getRecord() throws com.daffodilwoods.database.resource.DException {
188      return iterator.getRecord();
189   }
190 
191   public Object   getColumnValues(_Reference[] parm1) throws com.daffodilwoods.database.resource.DException {
192     return iterator.getColumnValues(parm1);
193   }
194 
195   public Object   getColumnValues(_Reference parm1) throws com.daffodilwoods.database.resource.DException {
196     return iterator.getColumnValues(parm1);
197   }
198 
199   public _Iterator getBaseIteratorHasRecord(ColumnDetails parm1) throws com.daffodilwoods.database.resource.DException {
200      return iterator.getBaseIteratorHasRecord(parm1);
201   }
202 
203   public Object  [][] getFunctionalColumnMapping() throws DException {
204      return iterator.getFunctionalColumnMapping();
205   }
206 
207   public FieldBase field(_Reference reference) throws com.daffodilwoods.database.resource.DException  {
208      return iterator.field(reference);
209   }
210 
211   public FieldBase[] fields(_Reference[] references) throws com.daffodilwoods.database.resource.DException  {
212      return iterator.fields(references);
213   }
214 
215   public FieldBase[] fields(int[] columns) throws com.daffodilwoods.database.resource.DException  {
216      throw new java.lang.UnsupportedOperationException  ("Method fields() not yet implemented.");
217   }
218 
219   public void releaseResource() throws DException  {
220     iterator.releaseResource();
221   }
222 
223   public String   toString(){
224      return "ReverseIterator["+iterator+"]";
225   }
226 
227   public void setSpecificUnderlyingReferences(_Reference[] specificUnderlyingReferences) throws DException{
228     underlyingRef=specificUnderlyingReferences;
229     }
230 
231 }
232
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