<?xml version="1.0" encoding="UTF-8" standalone="no"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> <title>Transactional Cursors</title> <link rel="stylesheet" href="gettingStarted.css" type="text/css" /> <meta name="generator" content="DocBook XSL Stylesheets V1.62.4" /> <link rel="home" href="index.html" title="Getting Started with Berkeley DB Transaction Processing" /> <link rel="up" href="usingtxns.html" title="Chapter 3. Transaction Basics" /> <link rel="previous" href="nestedtxn.html" title="Nested Transactions" /> <link rel="next" href="txnindices.html" title="Secondary Indices with Transaction Applications" /> </head> <body> <div class="navheader"> <table width="100%" summary="Navigation header"> <tr> <th colspan="3" align="center">Transactional Cursors</th> </tr> <tr> <td width="20%" align="left"><a accesskey="p" href="nestedtxn.html">Prev</a> </td> <th width="60%" align="center">Chapter 3. Transaction Basics</th> <td width="20%" align="right"> <a accesskey="n" href="txnindices.html">Next</a></td> </tr> </table> <hr /> </div> <div class="sect1" lang="en" xml:lang="en"> <div class="titlepage"> <div> <div> <h2 class="title" style="clear: both"><a id="txncursor"></a>Transactional Cursors</h2> </div> </div> <div></div> </div> <p> You can transaction-protect your cursor operations by specifying a transaction handle at the time that you create your cursor. Beyond that, you do not ever provide a transaction handle directly to a cursor method. </p> <p> Note that if you transaction-protect a cursor, then you must make sure that the cursor is closed before you either commit or abort the transaction. For example: </p> <pre class="programlisting">#include "db_cxx.h" ... int main(void) { // Environment and database opens omitted ... DbTxn *txn = NULL; Dbc *cursorp = NULL; try { Dbt key, data; key.set_data(keystr); key.set_size((strlen(keystr) + 1) * sizeof(char)); key.set_data(datastr); key.set_size((strlen(datastr) + 1) * sizeof(char)); DbTxn *txn = NULL; myEnv.txn_begin(NULL, &txn, 0); try { // Get our cursor. Note that we pass the transaction handle here. db.cursor(txn, &cursorp, 0); // Perform our operations. Note that we do not pass a transaction // handle here. char *replacementString = "new string"; while (cursor->get(&key, &data, DB_NEXT) == 0) { data.set_data(void *)replacementString); data.set_size((strlen(replacementString) + 1) * sizeof(char)); cursor->put(&key, &data, DB_CURRENT); } // We're done. Commit the transaction. cursor->close(); txn->commit(0); } catch (DbException &e) { std::cerr << "Error in transaction: " << e.what() << std::endl; cursor->close(); txn->abort(); } } catch(DbException &e) { std::cerr << "Error opening database and environment: " << file_name << ", " << envHome << std::endl; std::cerr << e.what() << std::endl; } return (EXIT_SUCCESS); } </pre> </div> <div class="navfooter"> <hr /> <table width="100%" summary="Navigation footer"> <tr> <td width="40%" align="left"><a accesskey="p" href="nestedtxn.html">Prev</a> </td> <td width="20%" align="center"> <a accesskey="u" href="usingtxns.html">Up</a> </td> <td width="40%" align="right"> <a accesskey="n" href="txnindices.html">Next</a></td> </tr> <tr> <td width="40%" align="left" valign="top">Nested Transactions </td> <td width="20%" align="center"> <a accesskey="h" href="index.html">Home</a> </td> <td width="40%" align="right" valign="top"> Secondary Indices with Transaction Applications</td> </tr> </table> </div> </body> </html>