Import BSDDB 4.7.25 (as of svn r89086)
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Zachary Ware
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docs/api_c/db_cursor.html
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docs/api_c/db_cursor.html
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<!--$Id: db_cursor.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->cursor</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->cursor</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->cursor(DB *db,
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DB_TXN *txnid, DBC **cursorp, 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->cursor</b>
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<p>The DB->cursor method returns a created database cursor.</p>
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<p>Cursors may span threads, but only serially, that is, the application
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must serialize access to the cursor handle.</p>
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<p>The DB->cursor 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>cursorp</b><ul compact><li>The <b>cursorp</b> parameter references memory into which
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a pointer to the allocated cursor is copied.</ul>
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<b>flags</b><ul compact><li>The <b>flags</b> parameter must be set to 0 or by bitwise inclusively <b>OR</b>'ing together one
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or more of the following values:
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<br>
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<b><a name="DB_READ_COMMITTED">DB_READ_COMMITTED</a></b><ul compact><li>Configure a transactional cursor to have degree 2 isolation. This ensures
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the stability of the current data item read by this cursor but permits data
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read by this cursor to be modified or deleted prior to the commit of the
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transaction for this cursor.</ul>
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<b><a name="DB_READ_UNCOMMITTED">DB_READ_UNCOMMITTED</a></b><ul compact><li>Configure a transactional cursor to have degree 1 isolation. Read
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operations performed by the cursor may return modified but not yet
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committed data. Silently ignored if the <a href="../api_c/db_open.html#DB_READ_UNCOMMITTED">DB_READ_UNCOMMITTED</a>
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flag was not specified when the underlying database was opened.</ul>
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<b><a name="DB_WRITECURSOR">DB_WRITECURSOR</a></b><ul compact><li>Specify that the cursor will be used to update the database. The
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underlying database environment must have been opened using the
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<a href="../api_c/env_open.html#DB_INIT_CDB">DB_INIT_CDB</a> flag.</ul>
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<b><a name="DB_TXN_SNAPSHOT">DB_TXN_SNAPSHOT</a></b><ul compact><li>Configure a transactional cursor to operate with read-only
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<a href="../ref/transapp/read.html">snapshot isolation</a>. For databases
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with the <a href="../api_c/db_open.html#DB_MULTIVERSION">DB_MULTIVERSION</a> flag set, data values will be read as
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they are when the cursor is opened, without taking read locks. This
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flag implicitly begins a transaction that is committed when the cursor
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is closed. Silently ignored if <a href="../api_c/db_open.html#DB_MULTIVERSION">DB_MULTIVERSION</a> not set on the
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underlying database or if a transaction is supplied in the <b>txnid</b>
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parameter.</ul>
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<br></ul>
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<b>txnid</b><ul compact><li>Cursor operations are not automatically transaction-protected, even if
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the <a href="../api_c/env_set_flags.html#DB_AUTO_COMMIT">DB_AUTO_COMMIT</a> flag is specified to the
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<a href="../api_c/env_set_flags.html">DB_ENV->set_flags</a> or <a href="../api_c/db_open.html">DB->open</a> methods. If cursor operations are
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to be transaction-protected, the <b>txnid</b> parameter must be a
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transaction handle returned from <a href="../api_c/txn_begin.html">DB_ENV->txn_begin</a>; otherwise, NULL. To
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transaction-protect cursor operations, cursors must be opened and closed
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within the context of a transaction, and the <b>txnid</b> parameter
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specifies the transaction context in which the cursor may be used.</ul>
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<br>
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<br><b>Errors</b>
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<p>The DB->cursor 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>DB_REP_HANDLE_DEAD</b><ul compact><li>The database handle has been invalidated because a replication election
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unrolled a committed transaction.</ul>
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<br>
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<br>
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<b>DB_REP_LOCKOUT</b><ul compact><li>The operation was blocked by client/master synchronization.</ul>
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<br>
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<br>
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<b>EINVAL</b><ul compact><li>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/dbc_class.html">DBC</a>
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<br><b>See Also</b>
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<a href="../api_c/dbc_list.html">Database Cursors 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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