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<p>
You replace the data for a database record by using
<span>
<tt class="methodname">Dbc::put()</tt>
with the <tt class="literal">DB_CURRENT</tt> flag.
</span>
</p>
<a id="cxx_cursor9"></a>
<pre class="programlisting">#include <db_cxx.h>
#include <string.h>
...
Db my_database(NULL, 0);
Dbc *cursorp;
int ret;
char *key1str = "My first string";
char *replacement_data = "replace me";
try {
// Database open omitted
// Get the cursor
my_database.cursor(NULL, &cursorp, 0);
// Set up our DBTs
Dbt key(key1str, strlen(key1str) + 1);
Dbt data;
// Position the cursor */
ret = cursorp->get(&key, &data, DB_SET);
if (ret == 0) {
data.set_data(replacement_data);
data.set_size(strlen(replacement_data) + 1);
cursorp->put(&key, &data, DB_CURRENT);
}
} catch(DbException &e) {
my_database.err(e.get_errno(), "Error!");
} catch(std::exception &e) {
my_database.errx("Error! %s", e.what());
}
// Cursors must be closed
if (cursorp != NULL)
cursorp->close();
my_database.close(0);</pre>
<p>
Note that you cannot change a record's key using this method; the key
parameter is always ignored when you replace a record.
</p>
<p>
When replacing the data portion of a record, if you are replacing a
record that is a member of a sorted duplicates set, then the replacement
will be successful only if the new record sorts identically to the old
record. This means that if you are replacing a record that is a member
of a sorted duplicates set, and if you are using the default
lexicographic sort, then the replacement will fail due to violating the
sort order. However, if you
provide a custom sort routine that, for example, sorts based on just a
few bytes out of the data item, then potentially you can perform
a direct replacement and still not violate the restrictions described
here.
</p>
<p>
<span>Under these circumstances, if</span>
you want to replace the data contained by a duplicate record,
<span>
and you are not using a custom sort routine, then
</span>
delete the record and create a new record with the desired key and data.
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