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The Db Handle
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<div class="sect1" lang="en" xml:lang="en">
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<div>
<h2 class="title" style="clear: both"><a id="dbtruncate"></a>Db::truncate()</h2>
</div>
</div>
</div>
<pre class="programlisting">#include <db_cxx.h>
int
Db::truncate(DbTxn *txnid, u_int32_t *countp, u_int32_t flags);</pre>
<p>
The <code class="methodname">Db::truncate()</code> method empties the database, discarding all
records it contains. The number of records discarded from the
database is returned in <span class="bold"><strong>countp</strong></span>.
</p>
<p>
When called on a database configured with secondary indices using the
<a class="xref" href="dbassociate.html" title="Db::associate()">Db::associate()</a>
method, the <code class="methodname">Db::truncate()</code> method truncates the primary database and
all secondary indices. A count of the records discarded from the
primary database is returned.
</p>
<p>
It is an error to call the <code class="methodname">Db::truncate()</code> method on a database with
open cursors.
</p>
<p>
The <code class="methodname">Db::truncate()</code> <span>
<span>
method either returns a non-zero error value or throws an
exception that encapsulates a non-zero error value on
failure, and returns 0 on success.
</span>
</span>
</p>
<div class="sect2" lang="en" xml:lang="en">
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<div>
<h3 class="title"><a id="idp5975160"></a>Parameters</h3>
</div>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp5951776"></a>txnid</h4>
</div>
</div>
</div>
<p>
If the operation is part of an application-specified transaction, the
<span class="bold"><strong>txnid</strong></span> parameter is a transaction
handle returned from <a class="xref" href="txnbegin.html" title="DbEnv::txn_begin()">DbEnv::txn_begin()</a>; if the
operation is part of a Berkeley DB Concurrent Data Store group, the
<span class="bold"><strong>txnid</strong></span> parameter is a handle returned
from <a class="xref" href="envcdsgroup_begin.html" title="DbEnv::cdsgroup_begin()">DbEnv::cdsgroup_begin()</a>;
otherwise NULL. If no transaction handle is specified, but the
operation occurs in a transactional database, the operation will be
implicitly transaction protected.
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<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp5990384"></a>countp</h4>
</div>
</div>
</div>
<p>
The <span class="bold"><strong>countp</strong></span> parameter references
memory into which the number of records discarded from the database
is copied.
</p>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp5995384"></a>flags</h4>
</div>
</div>
</div>
<p>
The <span class="bold"><strong>flags</strong></span> parameter is currently
unused, and must be set to 0.
</p>
</div>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp5982536"></a>Errors</h3>
</div>
</div>
</div>
<p>
The <code class="methodname">Db::truncate()</code> <span>
<span>
method may fail and throw a <a class="link" href="dbexception.html" title="Chapter 6. The DbException Class">DbException</a>
exception, encapsulating one of the following non-zero errors, or return one
of the following non-zero errors:
</span>
</span>
</p>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp5979640"></a><span>DbDeadlockException or </span>DB_LOCK_DEADLOCK</h4>
</div>
</div>
</div>
<p>
A transactional database environment operation was selected to resolve
a deadlock.
</p>
<p>
<a class="xref" href="dbdeadlock.html" title="DbDeadlockException">DbDeadlockException</a> is thrown if
your Berkeley DB API is configured to throw exceptions.
Otherwise, <code class="literal">DB_LOCK_DEADLOCK</code> is returned.
</p>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp5992408"></a><span>DbLockNotGrantedException or </span>DB_LOCK_NOTGRANTED</h4>
</div>
</div>
</div>
<p>
A Berkeley DB Concurrent Data Store database environment configured
for lock timeouts was unable to grant a lock in the allowed time.
</p>
<p>
You attempted to open a database handle that is configured
for no waiting exclusive locking, but the exclusive lock could not be
immediately obtained. See
<a class="xref" href="dbset_lk_exclusive.html" title="Db::set_lk_exclusive()">Db::set_lk_exclusive()</a>
for more information.
</p>
<p>
<a class="xref" href="dblocknotgranted.html" title="DbLockNotGrantedException">DbLockNotGrantedException</a> is thrown if
your Berkeley DB API is configured to throw exceptions.
Otherwise, <code class="literal">DB_LOCK_NOTGRANTED</code> is returned.
</p>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp5901200"></a>EINVAL</h4>
</div>
</div>
</div>
<p>
If there are open cursors in the database; or if an invalid flag value or parameter was specified.
</p>
</div>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp5998016"></a>Class</h3>
</div>
</div>
</div>
<p>
<a class="link" href="db.html" title="Chapter 2. The Db Handle">Db</a>
</p>
</div>
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<div class="titlepage">
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<h3 class="title"><a id="idp5970480"></a>See Also</h3>
</div>
</div>
</div>
<p>
<a class="xref" href="db.html#dblist" title="Database and Related Methods">Database and Related Methods</a>
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