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Using Secondary Cursors
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Using Secondary Cursors
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<span>Using Secondary Cursors</span>
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<p>
Just like cursors on a primary database, you can use
<span>secondary cursors</span>
to iterate over the records in a secondary database. Like
<span>normal cursors,</span>
you can also use
<span>secondary cursors</span>
to search for specific records in a database, to seek to the first
or last record in the database, to get the next duplicate record,
and so forth. For a complete description on cursors and their capabilities, see
<a href="Cursors.html">Using Cursors</a>.
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However, when you use
<span>secondary cursors:</span>
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Any data returned is the data contained on the primary database
record referenced by the secondary record.
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<p>
<tt class="methodname">SecondaryCursor.getSearchBoth()</tt> and
related methods do not search based on a key/data pair. Instead, you
search based on a secondary key and a primary key. The data returned
is the primary data that most closely matches the two keys provided
for the search.
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For example, suppose you are using the databases, classes, and key
<span>creators</span>
described in <a href="keyCreator.html">Implementing Key
<span>Creators</span>
</a>.
Then the following searches for a person's
name in the secondary database, and deletes all secondary and primary
records that use that name.
</p>
<a id="java_index8"></a>
<pre class="programlisting">package db.GettingStarted;
import com.sleepycat.db.DatabaseEntry;
import com.sleepycat.db.LockMode;
import com.sleepycat.db.OperationStatus;
import com.sleepycat.db.SecondaryDatabase;
import com.sleepycat.db.SecondaryCursor;
...
try {
SecondaryDatabase mySecondaryDatabase = null;
// Database opens omitted for brevity
...
String secondaryName = "John Doe";
DatabaseEntry secondaryKey =
new DatabaseEntry(secondaryName.getBytes("UTF-8"));
DatabaseEntry foundData = new DatabaseEntry();
SecondaryCursor mySecCursor =
mySecondaryDatabase.openSecondaryCursor(null, null);
OperationStatus retVal = mySecCursor.getSearchKey(secondaryKey,
foundData,
LockMode.DEFAULT);
while (retVal == OperationStatus.SUCCESS) {
mySecCursor.delete();
retVal = mySecCursor.getNextDup(secondaryKey,
foundData,
LockMode.DEFAULT);
}
} catch (Exception e) {
// Exception handling goes here
}</pre>
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