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18 KiB
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<title>Db::del()</title>
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<link rel="start" href="index.html" title="Berkeley DB C++ API Reference" />
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<link rel="up" href="db.html" title="Chapter 2. The Db Handle" />
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<link rel="prev" href="dbcreate.html" title="Db" />
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<p>Library Version 11.2.5.2</p>
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<table width="100%" summary="Navigation header">
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<tr>
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<th colspan="3" align="center">Db::del()</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="dbcreate.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 2.
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The Db Handle
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</th>
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<td width="20%" align="right"> <a accesskey="n" href="dberr.html">Next</a></td>
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<div class="sect1" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h2 class="title" style="clear: both"><a id="dbdel"></a>Db::del()</h2>
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</div>
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</div>
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</div>
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<pre class="programlisting">#include <db_cxx.h>
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int
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Db::del(DbTxn *txnid, Dbt *key, u_int32_t flags);</pre>
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<p>
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The <code class="methodname">Db::del()</code> method removes key/data pairs from the database. The
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key/data pair associated with the specified <span class="bold"><strong>key</strong></span> is discarded from the database. In the
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presence of duplicate key values, all records associated with the
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designated key will be discarded.
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</p>
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<p>
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When called on a database that has been made into a secondary index
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using the <a class="xref" href="dbassociate.html" title="Db::associate()">Db::associate()</a> method, the
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<code class="methodname">Db::del()</code> method deletes the key/data pair from the primary database
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and all secondary indices.
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</p>
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<p>
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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
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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
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Queue or Recno database and the specified key exists, but was never explicitly created by
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the application or was later deleted. Unless otherwise specified, the
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<code class="methodname">Db::del()</code> <span>
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<span>
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method either returns a non-zero error value or throws an
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exception that encapsulates a non-zero error value on
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failure, and returns 0 on success.
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</span>
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</span>
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</p>
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<div class="sect2" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h3 class="title"><a id="id3559943"></a>Parameters</h3>
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</div>
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</div>
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</div>
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<div class="sect3" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h4 class="title"><a id="id3561244"></a>txnid</h4>
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</div>
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</div>
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</div>
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<p>
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If the operation is part of an application-specified transaction, the
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<span class="bold"><strong>txnid</strong></span> parameter is a transaction
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handle returned from <a class="xref" href="txnbegin.html" title="DbEnv::txn_begin()">DbEnv::txn_begin()</a>;
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if the operation is part of a Berkeley DB Concurrent Data Store group, the
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<span class="bold"><strong>txnid</strong></span> parameter is a handle returned
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from <a class="xref" href="envcdsgroup_begin.html" title="DbEnv::cdsgroup_begin()">DbEnv::cdsgroup_begin()</a>;
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otherwise NULL. If no transaction handle is specified, but the
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operation occurs in a transactional database, the operation will be
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implicitly transaction protected.
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</p>
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</div>
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<div class="sect3" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h4 class="title"><a id="id3560988"></a>key</h4>
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</div>
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</div>
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</div>
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<p>
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The key <a class="link" href="dbt.html" title="Chapter 4. The Dbt Handle">Dbt</a> operated on.
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</p>
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</div>
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<div class="sect3" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h4 class="title"><a id="id3559967"></a>flags</h4>
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</div>
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</div>
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</div>
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<p>
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The <span class="bold"><strong>flags</strong></span> parameter must be set to 0
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or one of the following values:
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</p>
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<div class="itemizedlist">
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<ul type="disc">
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<li>
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<p><a id="dbput_DB_CONSUME"></a>
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<code class="literal">DB_CONSUME</code>
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</p>
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<p>
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If the database is of type DB_QUEUE then this flag may be set to force the head of the queue
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to move to the first non-deleted item in the queue. Normally this is only done if the
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deleted item is exactly at the head when deleted.
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</p>
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</li>
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<li>
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<p><a id="del_DB_MULTIPLE"></a>
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<code class="literal">DB_MULTIPLE</code>
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</p>
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<p>
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Delete multiple data items using keys from the buffer to which the
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<span class="bold"><strong>key</strong></span> parameter refers.
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</p>
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<p>
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To delete records in bulk by key with the btree or hash access methods, construct a
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bulk buffer in the <span class="bold"><strong>key</strong></span>
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<a class="link" href="dbt.html" title="Chapter 4. The Dbt Handle">Dbt</a> using
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<a class="xref" href="dbmultipledatabuilder.html" title="DbMultipleDataBuilder">DbMultipleDataBuilder</a>.
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To delete records in bulk by record number, construct a bulk buffer in the
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<span class="bold"><strong>key</strong></span>
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<a class="link" href="dbt.html" title="Chapter 4. The Dbt Handle">Dbt</a> using
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<a class="xref" href="dbmultiplerecnodatabuilder.html" title="DbMultipleRecnoDataBuilder">DbMultipleRecnoDataBuilder</a>
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with a data size of zero.
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</p>
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<p>
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A successful bulk delete operation is logically equivalent to a loop through each
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key/data pair, performing a <a class="xref" href="dbdel.html" title="Db::del()">Db::del()</a> for each one.
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</p>
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<p>
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See the <a class="xref" href="dbt.html#dbtlist" title="DBT and Bulk Operations">DBT and Bulk Operations</a> for more information on
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working with bulk updates.
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</p>
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<p>
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The <code class="literal">DB_MULTIPLE</code> flag may only be used alone.
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</p>
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</li>
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<li>
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<p><a id="del_DB_MULTIPLE_KEY"></a>
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<code class="literal">DB_MULTIPLE_KEY</code>
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</p>
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<p>
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Delete multiple data items using keys and data from the buffer to which the
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<span class="bold"><strong>key</strong></span> parameter refers.
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</p>
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<p>
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To delete records in bulk with the btree or hash access methods, construct a bulk
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buffer in the <span class="bold"><strong>key</strong></span>
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<a class="link" href="dbt.html" title="Chapter 4. The Dbt Handle">Dbt</a> using
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<a class="xref" href="dbmultiplekeydatabuilder.html" title="DbMultipleKeyDataBuilder">DbMultipleKeyDataBuilder</a>.
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To delete records in bulk with the recno or hash access methods, construct a bulk
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buffer in the <span class="bold"><strong>key</strong></span>
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<a class="link" href="dbt.html" title="Chapter 4. The Dbt Handle">Dbt</a> using
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<a class="xref" href="dbmultiplerecnodatabuilder.html" title="DbMultipleRecnoDataBuilder">DbMultipleRecnoDataBuilder</a>.
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</p>
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<p>
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See the <a class="xref" href="dbt.html#dbtlist" title="DBT and Bulk Operations">DBT and Bulk Operations</a> for more information on
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working with bulk updates.
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</p>
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<p>
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The <code class="literal">DB_MULTIPLE_KEY</code> flag may only be used alone.
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</p>
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</li>
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</ul>
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</div>
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</div>
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</div>
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<div class="sect2" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h3 class="title"><a id="id3561383"></a>Errors</h3>
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</div>
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</div>
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</div>
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<p>
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The <code class="methodname">Db::del()</code> <span>
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<span>
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method may fail and throw a <a class="link" href="dbexception.html" title="Chapter 6. The DbException Class">DbException</a>
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exception, encapsulating one of the following non-zero errors, or return one
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of the following non-zero errors:
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</span>
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</span>
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</p>
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<div class="sect3" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h4 class="title"><a id="id3561555"></a>DB_FOREIGN_CONFLICT</h4>
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</div>
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</div>
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</div>
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<p>
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A <a class="link" href="dbassociate_foreign.html" title="Db::associate_foreign()">foreign key constraint violation</a>
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has occurred. This can be caused by one of two things:
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</p>
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<div class="orderedlist">
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<ol type="1">
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<li>
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<p>
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An attempt was made to add a record to a
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constrained database, and the key used for that
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record does not exist in the foreign key
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database.
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</p>
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</li>
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<li>
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<p>
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<a class="link" href="dbassociate_foreign.html#associate_foreign_DB_FOREIGN_ABORT">DB_FOREIGN_ABORT</a>
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was declared for a foreign key database, and then
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subsequently a record was deleted from the
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foreign key database without first removing it
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from the constrained secondary database.
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</p>
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</li>
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</ol>
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</div>
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</div>
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<div class="sect3" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h4 class="title"><a id="id3561515"></a><span>DbDeadlockException or </span>DB_LOCK_DEADLOCK</h4>
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</div>
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</div>
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</div>
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<p>
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A transactional database environment operation was selected to resolve
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a deadlock.
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</p>
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<p>
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<a class="xref" href="dbdeadlock.html" title="DbDeadlockException">DbDeadlockException</a> is thrown if
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your Berkeley DB API is configured to throw exceptions.
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Otherwise, <code class="literal">DB_LOCK_DEADLOCK</code> is returned.
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</p>
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</div>
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<div class="sect3" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h4 class="title"><a id="id3561162"></a><span>DbLockNotGrantedException or </span>DB_LOCK_NOTGRANTED</h4>
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</div>
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</div>
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</div>
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<p>
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A Berkeley DB Concurrent Data Store database environment configured
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for lock timeouts was unable to grant a lock in the allowed time.
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</p>
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<p>
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<a class="xref" href="dblocknotgranted.html" title="DbLockNotGrantedException">DbLockNotGrantedException</a> is thrown if
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your Berkeley DB API is configured to throw exceptions.
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Otherwise, <code class="literal">DB_LOCK_NOTGRANTED</code> is returned.
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</p>
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</div>
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<div class="sect3" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h4 class="title"><a id="id3560959"></a> <span>DbRepHandleDeadException or</span> DB_REP_HANDLE_DEAD</h4>
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</div>
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</div>
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</div>
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<p>
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When a client synchronizes with the master, it is possible for committed
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transactions to be rolled back. This invalidates all the database and cursor
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handles opened in the replication environment. Once this occurs, an attempt to use
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such a handle will
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<span>
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throw a <a class="xref" href="dbrephandledead.html" title="DbRepHandleDeadException">DbRepHandleDeadException</a> (if
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your application is configured to throw exceptions), or
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</span>
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return <code class="literal">DB_REP_HANDLE_DEAD</code>.
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The application will need to discard the handle and open a new one in order to
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continue processing.
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</p>
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</div>
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<div class="sect3" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h4 class="title"><a id="id3561497"></a><span>DbDeadlockException or </span>DB_REP_LOCKOUT</h4>
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</div>
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</div>
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</div>
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<p>
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The operation was blocked by client/master synchronization.
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</p>
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<p>
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<a class="xref" href="dbdeadlock.html" title="DbDeadlockException">DbDeadlockException</a> is thrown if
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your Berkeley DB API is configured to throw exceptions.
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Otherwise, <code class="literal">DB_REP_LOCKOUT</code> is returned.
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</p>
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</div>
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<div class="sect3" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h4 class="title"><a id="id3561822"></a>DB_SECONDARY_BAD</h4>
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</div>
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</div>
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</div>
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<p>
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A secondary index references a nonexistent primary key.
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</p>
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</div>
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<div class="sect3" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h4 class="title"><a id="id3561561"></a>EACCES</h4>
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</div>
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</div>
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</div>
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<p>
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An attempt was made to modify a read-only database.
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</p>
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</div>
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<div class="sect3" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h4 class="title"><a id="id3561823"></a>EINVAL</h4>
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</div>
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</div>
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</div>
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<p>
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An invalid flag value or parameter was specified.
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</p>
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</div>
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</div>
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<div class="sect2" lang="en" xml:lang="en">
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<div class="titlepage">
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||
<div>
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<div>
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<h3 class="title"><a id="id3561465"></a>Class</h3>
|
||
</div>
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||
</div>
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||
</div>
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<p>
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||
<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="id3561798"></a>See Also</h3>
|
||
</div>
|
||
</div>
|
||
</div>
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||
<p>
|
||
<a class="xref" href="db.html#dblist" title="Database and Related Methods">Database and Related Methods</a>
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||
</p>
|
||
</div>
|
||
</div>
|
||
<div class="navfooter">
|
||
<hr />
|
||
<table width="100%" summary="Navigation footer">
|
||
<tr>
|
||
<td width="40%" align="left"><a accesskey="p" href="dbcreate.html">Prev</a> </td>
|
||
<td width="20%" align="center">
|
||
<a accesskey="u" href="db.html">Up</a>
|
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</td>
|
||
<td width="40%" align="right"> <a accesskey="n" href="dberr.html">Next</a></td>
|
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</tr>
|
||
<tr>
|
||
<td width="40%" align="left" valign="top">Db </td>
|
||
<td width="20%" align="center">
|
||
<a accesskey="h" href="index.html">Home</a>
|
||
</td>
|
||
<td width="40%" align="right" valign="top"> Db::err()</td>
|
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</tr>
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</table>
|
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</div>
|
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</body>
|
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</html>
|