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Berkeley DB version 4.4.20 |
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java.lang.Object com.sleepycat.db.JoinConfig
The configuration properties of a JoinCursor
.
The join cursor configuration is specified when calling 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);
Database.join
,
JoinCursor
Field Summary | |
static JoinConfig |
DEFAULT
Default configuration used if null is passed to Database.join |
Constructor Summary | |
JoinConfig()
Creates an instance with the system's default settings. |
Method Summary | |
boolean |
getNoSort()
Returns whether automatic sorting of the input cursors is disabled. |
void |
setNoSort(boolean noSort)
Specifies whether automatic sorting of the input cursors is disabled. |
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Field Detail |
public static final JoinConfig DEFAULT
Database.join
Constructor Detail |
public JoinConfig()
Method Detail |
public void setNoSort(boolean noSort)
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.
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
.
noSort
- whether automatic sorting of the input cursors is disabled.
Database.join
public boolean getNoSort()
setNoSort(boolean)
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Berkeley DB version 4.4.20 |
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