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Java > Open Source Codes > org > apache > derby > iapi > store > access > ScanInfo


1 /*
2
3    Derby - Class org.apache.derby.iapi.store.access.ScanInfo
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.error.StandardException;
25
26 import java.util.Properties JavaDoc;
27
28 /**
29
30   This object provides performance information related to an open scan.
31   The information is accumulated during operations on a ScanController() and
32   then copied into this object and returned by a call to
33   ScanController.getStatistic().
34
35   @see GenericScanController#getScanInfo()
36
37 **/
38
39 public interface ScanInfo
40 {
41     /**
42      * Return all information gathered about the scan.
43      * <p>
44      * This routine returns a list of properties which contains all information
45      * gathered about the scan. If a Property is passed in, then that property
46      * list is appeneded to, otherwise a new property object is created and
47      * returned.
48      * <p>
49      * Not all scans may support all properties, if the property is not
50      * supported then it will not be returned. The following is a list of
51      * properties that may be returned. These names have been internationalized,
52      * the names shown here are the old, non-internationalized names:
53      *
54      * scanType
55      * - type of the scan being performed:
56      * btree
57      * heap
58      * sort
59      * numPagesVisited
60      * - the number of pages visited during the scan. For btree scans
61      * this number only includes the leaf pages visited.
62      * numDeletedRowsVisited
63      * - the number of deleted rows visited during the scan. This
64      * number includes only those rows marked deleted.
65      * numRowsVisited
66      * - the number of rows visited during the scan. This number
67      * includes all rows, including: those marked deleted, those
68      * that don't meet qualification, ...
69      * numRowsQualified
70      * - the number of rows which met the qualification.
71      * treeHeight (btree's only)
72      * - for btree's the height of the tree. A tree with one page
73      * has a height of 1. Total number of pages visited in a btree
74      * scan is (treeHeight - 1 + numPagesVisited).
75      * numColumnsFetched
76      * - the number of columns Fetched - partial scans will result
77      * in fetching less columns than the total number in the scan.
78      * columnsFetchedBitSet
79      * - The BitSet.toString() method called on the validColumns arg.
80      * to the scan, unless validColumns was set to null, and in that
81      * case we will return "all".
82      * NOTE - this list will be expanded as more information about the scan
83      * is gathered and returned.
84      *
85      * @param prop Property list to fill in.
86      *
87      * @exception StandardException Standard exception policy.
88      **/
89     Properties JavaDoc getAllScanInfo(Properties JavaDoc prop)
90         throws StandardException;
91 }
92
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