com.sleepycat.je.JoinConfig Maven / Gradle / Ivy
/*-
* Copyright (C) 2002, 2018, Oracle and/or its affiliates. All rights reserved.
*
* This file was distributed by Oracle as part of a version of Oracle Berkeley
* DB Java Edition made available at:
*
* http://www.oracle.com/technetwork/database/database-technologies/berkeleydb/downloads/index.html
*
* Please see the LICENSE file included in the top-level directory of the
* appropriate version of Oracle Berkeley DB Java Edition for a copy of the
* license and additional information.
*/
package com.sleepycat.je;
/**
* The configuration properties of a JoinCursor. The join cursor
* configuration is specified when calling {@link Database#join Database.join}.
*
* To create a configuration object with default attributes:
*
*
* JoinConfig config = new JoinConfig();
*
*
* To set custom attributes:
*
*
* JoinConfig config = new JoinConfig();
* config.setNoSort(true);
*
*
* @see Database#join Database.join
* @see JoinCursor
*/
public class JoinConfig implements Cloneable {
/**
* Default configuration used if null is passed to {@link
* com.sleepycat.je.Database#join Database.join}.
*/
public static final JoinConfig DEFAULT = new JoinConfig();
private boolean noSort;
/**
* Creates an instance with the system's default settings.
*/
public JoinConfig() {
}
/**
* Specifies whether automatic sorting of the input cursors is disabled.
*
* Joined values are retrieved by doing a sequential iteration over the
* first cursor in the cursor array, and a nested iteration over each
* following cursor in the order they are specified in the array. This
* requires database traversals to search for the current datum in all the
* cursors after the first. For this reason, the best join performance
* normally results from sorting the cursors from the one that refers to
* the least number of data items to the one that refers to the
* most. Unless this method is called with true, Database.join
* does this sort on behalf of its caller using the {@link
* Cursor#countEstimate} method.
*
* If the data are structured so that cursors with many data items also
* share many common elements, higher performance will result from listing
* those cursors before cursors with fewer data items; that is, a sort
* order other than the default. Calling this method permits applications
* to perform join optimization prior to calling
* Database.join.
*
* @param noSort whether automatic sorting of the input cursors is
* disabled.
*
* @see Database#join Database.join
*
* @return this
*/
public JoinConfig setNoSort(boolean noSort) {
setNoSortVoid(noSort);
return this;
}
/**
* @hidden
* The void return setter for use by Bean editors.
*/
public void setNoSortVoid(boolean noSort) {
this.noSort = noSort;
}
/**
* Returns whether automatic sorting of the input cursors is disabled.
*
* @return whether automatic sorting of the input cursors is disabled.
*
* @see #setNoSort
*/
public boolean getNoSort() {
return noSort;
}
/**
* Returns a copy of this configuration object.
*/
@Override
public JoinConfig clone() {
try {
return (JoinConfig) super.clone();
} catch (CloneNotSupportedException willNeverOccur) {
return null;
}
}
/**
* Returns the values for each configuration attribute.
*
* @return the values for each configuration attribute.
*/
@Override
public String toString() {
return "noSort=" + noSort +
"\n";
}
}