107 lines
5.7 KiB
HTML
107 lines
5.7 KiB
HTML
<!--$Id: logc_get.html 63573 2008-05-23 21:43:21Z trent.nelson $-->
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<!--Copyright (c) 1997,2008 Oracle. All rights reserved.-->
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<!--See the file LICENSE for redistribution information.-->
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<html>
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<head>
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<title>Berkeley DB: DB_LOGC->get</title>
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<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit.">
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<meta name="keywords" content="embedded,database,programmatic,toolkit,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,Java,C,C++">
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</head>
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<body bgcolor=white>
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<table width="100%"><tr valign=top>
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<td>
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<b>DB_LOGC->get</b>
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</td>
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<td align=right>
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<a href="../api_c/api_core.html"><img src="../images/api.gif" alt="API"></a>
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<a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a></td>
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</tr></table>
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<hr size=1 noshade>
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<tt>
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<b><pre>
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#include <db.h>
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<p>
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int
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DB_LOGC->get(DB_LOGC *logc, DB_LSN *lsn, DBT *data, u_int32_t flags);
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</pre></b>
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<hr size=1 noshade>
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<b>Description: DB_LOGC->get</b>
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<p>The DB_LOGC->get method returns records from the log.</p>
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<p>Unless otherwise specified, the DB_LOGC->get method
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returns a non-zero error value on failure
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and 0 on success.
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</p>
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<b>Parameters</b> <br>
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<b>data</b><ul compact><li>The data field of the <b>data</b> structure is set to the record
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retrieved, and the size field indicates the number of bytes in the
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record. See <a href="../api_c/dbt_class.html">DBT</a> for a description of other fields in the
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<b>data</b> structure. The <a href="../api_c/dbt_class.html#DB_DBT_MALLOC">DB_DBT_MALLOC</a>,
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<a href="../api_c/dbt_class.html#DB_DBT_REALLOC">DB_DBT_REALLOC</a> and <a href="../api_c/dbt_class.html#DB_DBT_USERMEM">DB_DBT_USERMEM</a> flags may be specified
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for any <a href="../api_c/dbt_class.html">DBT</a> used for data retrieval.</ul>
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<b>flags</b><ul compact><li>The <b>flags</b> parameter must be set to one of the following values:
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<br>
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<b><a name="DB_CURRENT">DB_CURRENT</a></b><ul compact><li>Return the log record to which the log currently refers.</ul>
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<b><a name="DB_FIRST">DB_FIRST</a></b><ul compact><li>The first record from any of the log files found in the log directory
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is returned in the <b>data</b> parameter.
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The <b>lsn</b> parameter is overwritten with the <a href="../api_c/lsn_class.html">DB_LSN</a> of the
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record returned.
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<p>The DB_LOGC->get method will return <a href="../ref/program/errorret.html#DB_NOTFOUND">DB_NOTFOUND</a> if DB_FIRST is set and the log is empty.
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</p></ul>
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<b><a name="DB_LAST">DB_LAST</a></b><ul compact><li>The last record in the log is returned in the <b>data</b> parameter.
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The <b>lsn</b> parameter is overwritten with the <a href="../api_c/lsn_class.html">DB_LSN</a> of the
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record returned.
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<p>The DB_LOGC->get method will return <a href="../ref/program/errorret.html#DB_NOTFOUND">DB_NOTFOUND</a> if DB_LAST is set and the log is empty.
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</p></ul>
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<b><a name="DB_NEXT">DB_NEXT</a></b><ul compact><li>The current log position is advanced to the next record in the log, and
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that record is returned in the <b>data</b> parameter. The <b>lsn</b>
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parameter is overwritten with the <a href="../api_c/lsn_class.html">DB_LSN</a> of the record returned.
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<p>If the cursor has not been initialized via DB_FIRST, DB_LAST, DB_SET,
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DB_NEXT, or DB_PREV, DB_LOGC->get will return the first record in
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the log.</p>
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<p>The DB_LOGC->get method will return <a href="../ref/program/errorret.html#DB_NOTFOUND">DB_NOTFOUND</a> if DB_NEXT is set and the last log record has already been
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returned or the log is empty.
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</p></ul>
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<b><a name="DB_PREV">DB_PREV</a></b><ul compact><li>The current log position is advanced to the previous record in the log,
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and that record is returned in the <b>data</b> parameter. The
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<b>lsn</b> parameter is overwritten with the <a href="../api_c/lsn_class.html">DB_LSN</a> of the record
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returned.
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<p>If the cursor has not been initialized via DB_FIRST, DB_LAST, DB_SET,
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DB_NEXT, or DB_PREV, DB_LOGC->get will return the last record in the
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log.</p>
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<p>The DB_LOGC->get method will return <a href="../ref/program/errorret.html#DB_NOTFOUND">DB_NOTFOUND</a> if DB_PREV is set and the first log record has already been
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returned or the log is empty.
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</p></ul>
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<b><a name="DB_SET">DB_SET</a></b><ul compact><li>Retrieve the record specified by the <b>lsn</b> parameter.</ul>
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<br></ul>
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<b>lsn</b><ul compact><li>When the <b>flag</b> parameter is set to DB_CURRENT,
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DB_FIRST, DB_LAST, DB_NEXT or DB_PREV,
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the <b>lsn</b> parameter is overwritten with the <a href="../api_c/lsn_class.html">DB_LSN</a> value
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of the record retrieved. When <b>flag</b> is set to DB_SET,
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the <b>lsn</b> parameter is the <a href="../api_c/lsn_class.html">DB_LSN</a> value of the record to
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be retrieved.</ul>
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<br>
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<br><b>Errors</b>
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<p>The DB_LOGC->get method
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may fail and return one of the following non-zero errors:</p>
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<br>
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<b>EINVAL</b><ul compact><li>If the DB_CURRENT flag was set and the log cursor has not yet
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been initialized;
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the DB_CURRENT, DB_NEXT, or DB_PREV flags were
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set and the log was opened with the DB_THREAD flag set;
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the DB_SET flag was set and the specified log sequence number
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does not appear in the log; or if an
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invalid flag value or parameter was specified.</ul>
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<br>
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<hr size=1 noshade>
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<br><b>Class</b>
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<a href="../api_c/env_class.html">DB_ENV</a>, <a href="../api_c/logc_class.html">DB_LOGC</a>, <a href="../api_c/lsn_class.html">DB_LSN</a>
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<br><b>See Also</b>
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<a href="../api_c/log_list.html">Logging Subsystem and Related Methods</a>
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</tt>
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<table width="100%"><tr><td><br></td><td align=right>
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<a href="../api_c/api_core.html"><img src="../images/api.gif" alt="API"></a><a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a>
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</td></tr></table>
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<p><font size=1>Copyright (c) 1996,2008 Oracle. All rights reserved.</font>
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</body>
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</html>
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