mirror of
https://github.com/yasuhirokimura/db18
synced 2026-06-08 18:29:23 +00:00
Yasuhiro KIMURA
138 lines
5.1 KiB
HTML
138 lines
5.1 KiB
HTML
<?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>Opening databases within the environment</title>
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<link rel="stylesheet" href="gettingStarted.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 Programmer's Reference Guide" />
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<link rel="up" href="env.html" title="Chapter 9. The Berkeley DB Environment" />
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<link rel="prev" href="env_size.html" title="Sizing a database environment" />
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<link rel="next" href="env_error.html" title="Error support" />
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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 18.1.40</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">Opening databases within the
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environment</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="env_size.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 9. The Berkeley DB Environment </th>
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<td width="20%" align="right"> <a accesskey="n" href="env_error.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="env_open"></a>Opening databases within the
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environment</h2>
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</div>
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</div>
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</div>
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<p>
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Once the environment has been created, database handles may
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be created and then opened within the environment. This is
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done by calling the <a href="../api_reference/C/dbcreate.html" class="olink">db_create()</a> function and specifying the
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appropriate environment as an argument.
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</p>
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<p>
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File naming, database operations, and error handling will
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all be done as specified for the environment. For example, if
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the <a href="../api_reference/C/envopen.html#envopen_DB_INIT_LOCK" class="olink">DB_INIT_LOCK</a> or <a href="../api_reference/C/envopen.html#envopen_DB_INIT_CDB" class="olink">DB_INIT_CDB</a> flags were specified when
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the environment was created or joined, database operations
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will automatically perform all necessary locking operations
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for the application.
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</p>
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<p>
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The following is a simple example of opening two databases
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within a database environment:
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</p>
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<a id="prog_env28"></a>
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<pre class="programlisting">DB_ENV *dbenv;
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DB *dbp1, *dbp2;
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int ret;
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dbenv = NULL;
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dbp1 = dbp2 = NULL;
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/*
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* Create an environment and initialize it for additional error
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* reporting.
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*/
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if ((ret = db_env_create(&dbenv, 0)) != 0) {
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fprintf(errfp, "%s: %s\n", progname, db_strerror(ret));
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return (ret);
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}
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dbenv->set_errfile(dbenv, errfp);
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dbenv->set_errpfx(dbenv, progname);
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/* Open an environment with just a memory pool. */
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if ((ret =
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dbenv->open(dbenv, home, DB_CREATE | DB_INIT_MPOOL, 0)) != 0) {
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dbenv->err(dbenv, ret, "environment open: %s", home);
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goto err;
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}
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/* Open database #1. */
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if ((ret = db_create(&dbp1, dbenv, 0)) != 0) {
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dbenv->err(dbenv, ret, "database create");
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goto err;
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}
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if ((ret = dbp1->open(dbp1,
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NULL, DATABASE1, NULL, DB_BTREE, DB_CREATE, 0664)) != 0) {
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dbenv->err(dbenv, ret, "DB->open: %s", DATABASE1);
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goto err;
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}
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/* Open database #2. */
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if ((ret = db_create(&dbp2, dbenv, 0)) != 0) {
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dbenv->err(dbenv, ret, "database create");
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goto err;
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}
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if ((ret = dbp2->open(dbp2,
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NULL, DATABASE2, NULL, DB_HASH, DB_CREATE, 0664)) != 0) {
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dbenv->err(dbenv, ret, "DB->open: %s", DATABASE2);
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goto err;
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}
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return (0);
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err: if (dbp2 != NULL)
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(void)dbp2->close(dbp2, 0);
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if (dbp1 != NULL)
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(void)dbp1->close(dbp1, 0);
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(void)dbenv->close(dbenv, 0);
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return (1);
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}</pre>
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</div>
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<div class="navfooter">
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<hr />
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<table width="100%" summary="Navigation footer">
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<tr>
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<td width="40%" align="left"><a accesskey="p" href="env_size.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="env.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="env_error.html">Next</a></td>
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</tr>
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<tr>
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<td width="40%" align="left" valign="top">Sizing a database environment </td>
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<td width="20%" align="center">
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<a accesskey="h" href="index.html">Home</a>
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</td>
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<td width="40%" align="right" valign="top"> Error support</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>
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