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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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<th colspan="3" align="center">Db::del()</th>
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<td width="20%" align="left"><a accesskey="p" href="dbcreate.html">Prev</a> </td>
<th width="60%" align="center">Chapter 2.
The Db Handle
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<div class="sect1" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h2 class="title" style="clear: both"><a id="dbdel"></a>Db::del()</h2>
</div>
</div>
</div>
<pre class="programlisting">#include <db_cxx.h>
int
Db::del(DbTxn *txnid, Dbt *key, u_int32_t flags);</pre>
<p>
The <code class="methodname">Db::del()</code> method removes key/data pairs from the database. The
key/data pair associated with the specified <span class="bold"><strong>key</strong></span> is discarded from the database. In the
presence of duplicate key values, all records associated with the
designated key will be discarded.
</p>
<p>
When called on a database that has been made into a secondary index
using the <a class="xref" href="dbassociate.html" title="Db::associate()">Db::associate()</a> method, the
<code class="methodname">Db::del()</code> method deletes the key/data pair from the primary database
and all secondary indices.
</p>
<p>
The <code class="methodname">Db::del()</code> method will return <a href="../../programmer_reference/program_errorret.html#program_errorret.DB_NOTFOUND" class="olink">DB_NOTFOUND</a> if the specified key
is not in the database. The <code class="methodname">Db::del()</code> method will return <a href="../../programmer_reference/program_errorret.html#program_errorret.DB_KEYEMPTY" class="olink">DB_KEYEMPTY</a> if the database is a
Queue or Recno database and the specified key exists, but was never explicitly created by
the application or was later deleted. Unless otherwise specified, the
<code class="methodname">Db::del()</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">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idm1381400"></a>Parameters</h3>
</div>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp4332848"></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.
</p>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idm2188096"></a>key</h4>
</div>
</div>
</div>
<p>
The key <a class="link" href="dbt.html" title="Chapter 4. The Dbt Handle">Dbt</a> operated on.
</p>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp3450752"></a>flags</h4>
</div>
</div>
</div>
<p>
The <span class="bold"><strong>flags</strong></span> parameter must be set to 0
or one of the following values:
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p><a id="dbput_DB_CONSUME"></a>
<code class="literal">DB_CONSUME</code>
</p>
<p>
If the database is of type DB_QUEUE then this flag may be set to force the head of the queue
to move to the first non-deleted item in the queue. Normally this is only done if the
deleted item is exactly at the head when deleted.
</p>
</li>
<li>
<p><a id="del_DB_MULTIPLE"></a>
<code class="literal">DB_MULTIPLE</code>
</p>
<p>
Delete multiple data items using keys from the buffer to which the
<span class="bold"><strong>key</strong></span> parameter refers.
</p>
<p>
To delete records in bulk by key with the btree or hash access methods, construct a
bulk buffer in the <span class="bold"><strong>key</strong></span>
<a class="link" href="dbt.html" title="Chapter 4. The Dbt Handle">Dbt</a> using
<a class="xref" href="dbmultipledatabuilder.html" title="DbMultipleDataBuilder">DbMultipleDataBuilder</a>.
To delete records in bulk by record number, construct a bulk buffer in the
<span class="bold"><strong>key</strong></span>
<a class="link" href="dbt.html" title="Chapter 4. The Dbt Handle">Dbt</a> using
<a class="xref" href="dbmultiplerecnodatabuilder.html" title="DbMultipleRecnoDataBuilder">DbMultipleRecnoDataBuilder</a>
with a data size of zero.
</p>
<p>
A successful bulk delete operation is logically equivalent to a loop through each
key/data pair, performing a <a class="xref" href="dbdel.html" title="Db::del()">Db::del()</a> for each one.
</p>
<p>
See the <a class="xref" href="dbt.html#dbtlist" title="DBT and Bulk Operations">DBT and Bulk Operations</a> for more information on
working with bulk updates.
</p>
<p>
The <code class="literal">DB_MULTIPLE</code> flag may only be used alone.
</p>
</li>
<li>
<p><a id="del_DB_MULTIPLE_KEY"></a>
<code class="literal">DB_MULTIPLE_KEY</code>
</p>
<p>
Delete multiple data items using keys and data from the buffer to which the
<span class="bold"><strong>key</strong></span> parameter refers.
</p>
<p>
To delete records in bulk with the btree or hash access methods, construct a bulk
buffer in the <span class="bold"><strong>key</strong></span>
<a class="link" href="dbt.html" title="Chapter 4. The Dbt Handle">Dbt</a> using
<a class="xref" href="dbmultiplekeydatabuilder.html" title="DbMultipleKeyDataBuilder">DbMultipleKeyDataBuilder</a>.
To delete records in bulk with the recno or hash access methods, construct a bulk
buffer in the <span class="bold"><strong>key</strong></span>
<a class="link" href="dbt.html" title="Chapter 4. The Dbt Handle">Dbt</a> using
<a class="xref" href="dbmultiplerecnodatabuilder.html" title="DbMultipleRecnoDataBuilder">DbMultipleRecnoDataBuilder</a>.
</p>
<p>
See the <a class="xref" href="dbt.html#dbtlist" title="DBT and Bulk Operations">DBT and Bulk Operations</a> for more information on
working with bulk updates.
</p>
<p>
The <code class="literal">DB_MULTIPLE_KEY</code> flag may only be used alone.
</p>
</li>
</ul>
</div>
</div>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp465120"></a>Errors</h3>
</div>
</div>
</div>
<p>
The <code class="methodname">Db::del()</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="idp2592168"></a>DB_FOREIGN_CONFLICT</h4>
</div>
</div>
</div>
<p>
A <a class="link" href="dbassociate_foreign.html" title="Db::associate_foreign()">foreign key constraint violation</a>
has occurred. This can be caused by one of two things:
</p>
<div class="orderedlist">
<ol type="1">
<li>
<p>
An attempt was made to add a record to a
constrained database, and the key used for that
record does not exist in the foreign key
database.
</p>
</li>
<li>
<p>
<a class="link" href="dbassociate_foreign.html#associate_foreign_DB_FOREIGN_ABORT">DB_FOREIGN_ABORT</a>
was declared for a foreign key database, and then
subsequently a record was deleted from the
foreign key database without first removing it
from the constrained secondary database.
</p>
</li>
</ol>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp2478240"></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="idp1954888"></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="idp1807704"></a> <span>DbRepHandleDeadException or</span> DB_REP_HANDLE_DEAD</h4>
</div>
</div>
</div>
<p>
When a client synchronizes with the master, it is possible for committed
transactions to be rolled back. This invalidates all the database and cursor
handles opened in the replication environment. Once this occurs, an attempt to use
such a handle will
<span>
throw a <a class="xref" href="dbrephandledead.html" title="DbRepHandleDeadException">DbRepHandleDeadException</a> (if
your application is configured to throw exceptions), or
</span>
return <code class="literal">DB_REP_HANDLE_DEAD</code>.
The application will need to discard the handle and open a new one in order to
continue processing.
</p>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp1781496"></a><span>DbDeadlockException or </span>DB_REP_LOCKOUT</h4>
</div>
</div>
</div>
<p>
The operation was blocked by client/master synchronization.
</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_REP_LOCKOUT</code> is returned.
</p>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idm545304"></a>DB_SECONDARY_BAD</h4>
</div>
</div>
</div>
<p>
A secondary index references a nonexistent primary key.
</p>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp1092920"></a>EACCES</h4>
</div>
</div>
</div>
<p>
An attempt was made to modify a read-only database.
</p>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp307416"></a>EINVAL</h4>
</div>
</div>
</div>
<p>
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="idp903376"></a>Class</h3>
</div>
</div>
</div>
<p>
<a class="link" href="db.html" title="Chapter 2. The Db Handle">Db</a>
</p>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp591520"></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>
</p>
</div>
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