BinaryOrderable


1   /*
2   
3      Derby - Class org.apache.derby.iapi.store.access.BinaryOrderable
4   
5      Licensed to the Apache Software Foundation (ASF) under one or more
6      contributor license agreements.  See the NOTICE file distributed with
7      this work for additional information regarding copyright ownership.
8      The ASF licenses this file to you under the Apache License, Version 2.0
9      (the "License"); you may not use this file except in compliance with
10     the License.  You may obtain a copy of the License at
11  
12        http://www.apache.org/licenses/LICENSE-2.0
13  
14     Unless required by applicable law or agreed to in writing, software
15     distributed under the License is distributed on an "AS IS" BASIS,
16     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17     See the License for the specific language governing permissions and
18     limitations under the License.
19  
20   */
21  
22  package org.apache.derby.iapi.store.access;
23  
24  import org.apache.derby.iapi.types.Orderable;
25  
26  import org.apache.derby.iapi.error.StandardException;
27  
28  import java.io.ObjectInput  ;
29  import java.io.IOException  ;
30  
31  /** 
32  
33    The Orderable interface represents a value that can
34    be linearly ordered.
35    <P>
36    Currently only supports linear (<, =, <=) operations.
37    Eventually we may want to do other types of orderings,
38    in which case there would probably be a number of interfaces
39    for each "class" of ordering.
40    <P>
41    The implementation must handle the comparison of null
42    values.  This may require some changes to the interface,
43    since (at least in some contexts) comparing a value with
44    null should return unknown instead of true or false.
45  
46  **/
47  
48  public interface BinaryOrderable extends Orderable
49  {
50      /**
51       * Compare this Orderable with a given Orderable for the purpose of
52       * index positioning.  This method treats nulls as ordered values -
53       * that is, it treats SQL null as equal to null and less than all
54       * other values.
55       *
56       * @param other     The Orderable to compare this one to.
57       *
58       * @return  <0 - this Orderable is less than other.
59       *           0 - this Orderable equals other.
60       *          >0 - this Orderable is greater than other.
61       *
62       *          The code should not explicitly look for -1, or 1.
63       *
64       * @exception IOException       Thrown on error
65       */
66      int binarycompare(
67      ObjectInput    in, 
68      Orderable    other) 
69          throws IOException  ;
70  
71      /**
72       * Compare this Orderable with a given Orderable for the purpose of
73       * qualification and sorting.  The caller gets to determine how nulls
74       * should be treated - they can either be ordered values or unknown
75       * values.
76       *
77       * @param op    Orderable.ORDER_OP_EQUALS means do an = comparison.
78       *              Orderable.ORDER_OP_LESSTHAN means compare this < other.
79       *              Orderable.ORDER_OP_LESSOREQUALS means compare this <= other.
80       * @param other The Orderable to compare this one to.
81       * @param orderedNulls  True means to treat nulls as ordered values,
82       *                      that is, treat SQL null as equal to null, and less
83       *                      than all other values.
84       *                      False means to treat nulls as unknown values,
85       *                      that is, the result of any comparison with a null
86       *                      is the UNKNOWN truth value.
87       * @param unknownRV     The return value to use if the result of the
88       *                      comparison is the UNKNOWN truth value.  In other
89       *                      words, if orderedNulls is false, and a null is
90       *                      involved in the comparison, return unknownRV.
91       *                      This parameter is not used orderedNulls is true.
92       *
93       * @return  true if the comparison is true.
94       *
95       * @exception IOException       Thrown on error
96       */
97      boolean binarycompare(
98      ObjectInput   in,
99      int         op, 
100     Orderable   other,
101     boolean     orderedNulls, 
102     boolean     unknownRV)
103                 throws IOException  ;
104 }
105
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