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<p>
<span>
You
</span>
can use transactions with your secondary indices so long as you
<span>
open the secondary index so that it supports transactions (that is,
you wrap the database open in a transaction, or use auto commit,
in the same way as when you open a primary transactional database).
</span>
<span>
In addition, you must make sure that when you associate the
secondary index with the primary database, the association is
performed using a transaction. The easiest thing to do here is
to simply specify <tt class="literal">DB_AUTO_COMMIT</tt> when you
perform the association.
</span>
</p>
<p>
All other aspects of using secondary indices with transactions are
identical to using secondary indices without transactions. In
addition, transaction-protecting
<span>
cursors opened against secondary indices is performed in
exactly the same way as when you use transactional cursors
against a primary database.
</span>
See <a href="txncursor.html">Transactional Cursors</a> for details.
</p>
<p>
Note that when you use transactions to protect your database writes, your secondary indices are protected from
corruption because updates to the primary and the secondaries are performed in a single atomic transaction.
</p>
<p>
For example:
</p>
<pre class="programlisting">#include <db.h>
...
DB_ENV *envp; /* Environment pointer */
DB *dbp, *sdbp; /* Primary and secondary DB handles */
u_int32_t flags; /* Primary database open flags */
int ret; /* Function return value */
/* Environment and primary database opens omitted */
/* Secondary */
ret = db_create(&sdbp, envp, 0);
if (ret != 0) {
/* Error handling goes here */
}
/* open the secondary database */
ret = sdbp->open(sdbp, /* DB structure pointer */
NULL, /* Transaction pointer */
"my_secdb.db", /* On-disk file that holds the database. */
NULL, /* Optional logical database name */
DB_BTREE, /* Database access method */
DB_AUTO_COMMIT, /* Open flags */
0); /* File mode (using defaults) */
if (ret != 0) {
/* Error handling goes here */
}
/* Now associate the secondary to the primary */
dbp->associate(dbp, /* Primary database */
NULL, /* TXN id */
sdbp, /* Secondary database */
get_sales_rep, /* Callback used for key creation. This
* is described in the Getting Started
* guide. */
DB_AUTO_COMMIT);/* Flags */</pre>
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