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HTML
387 lines
16 KiB
HTML
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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
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<title>DB->del()</title>
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<link rel="stylesheet" href="apiReference.css" type="text/css" />
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<meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
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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_create" />
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<link rel="next" href="dberr.html" title="DB->err()" />
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</head>
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<body>
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<div xmlns="" class="navheader">
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<div class="libver">
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<p>Library Version 11.2.5.2</p>
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</div>
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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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</tr>
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</table>
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<hr />
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</div>
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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.h>
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int
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DB->del(DB *db, DB_TXN *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 returns a non-zero error value on failure and 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="id3855029"></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="id3855040"></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="DB_ENV->txn_begin()">DB_ENV->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="DB_ENV->cdsgroup_begin()">DB_ENV->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="id3854926"></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="id3851145"></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="DB_MULTIPLE_WRITE_INIT.html" title="DB_MULTIPLE_WRITE_INIT">DB_MULTIPLE_WRITE_INIT</a> and
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<a class="xref" href="DB_MULTIPLE_WRITE_NEXT.html" title="DB_MULTIPLE_WRITE_NEXT">DB_MULTIPLE_WRITE_NEXT</a>. To
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delete records in bulk by record number, construct the
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<span class="bold"><strong>key</strong></span> <a class="link" href="dbt.html" title="Chapter 4. The DBT Handle">DBT</a> using
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<a class="xref" href="DB_MULTIPLE_RECNO_WRITE_INIT.html" title="DB_MULTIPLE_RECNO_WRITE_INIT">DB_MULTIPLE_RECNO_WRITE_INIT</a> and
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<a class="xref" href="DB_MULTIPLE_RECNO_WRITE_NEXT.html" title="DB_MULTIPLE_RECNO_WRITE_NEXT">DB_MULTIPLE_RECNO_WRITE_NEXT</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="DB_MULTIPLE_WRITE_INIT.html" title="DB_MULTIPLE_WRITE_INIT">DB_MULTIPLE_WRITE_INIT</a> and
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<a class="xref" href="DB_MULTIPLE_KEY_WRITE_NEXT.html" title="DB_MULTIPLE_KEY_WRITE_NEXT">DB_MULTIPLE_KEY_WRITE_NEXT</a>.
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To delete records in bulk with the recno or hash access methods, construct
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a 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="DB_MULTIPLE_RECNO_WRITE_INIT.html" title="DB_MULTIPLE_RECNO_WRITE_INIT">DB_MULTIPLE_RECNO_WRITE_INIT</a>
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and <a class="xref" href="DB_MULTIPLE_RECNO_WRITE_NEXT.html" title="DB_MULTIPLE_RECNO_WRITE_NEXT">DB_MULTIPLE_RECNO_WRITE_NEXT</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="id3855312"></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 return one 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="id3855227"></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="id3854521"></a>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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</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="id3854407"></a>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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</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="id3854807"></a> 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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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="id3855050"></a>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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</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="id3855473"></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>
|
|||
|
|
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="id3855635"></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="id3855642"></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="id3855230"></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="id3855162"></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>
|
|||
|
|
</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>
|
|||
|
|
</td>
|
|||
|
|
<td width="40%" align="right"> <a accesskey="n" href="dberr.html">Next</a></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr>
|
|||
|
|
<td width="40%" align="left" valign="top">db_create </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>
|
|||
|
|
</tr>
|
|||
|
|
</table>
|
|||
|
|
</div>
|
|||
|
|
</body>
|
|||
|
|
</html>
|