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BerkeleyDB-Core-Cxx-GSG.pdf
(402.24 KB)
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CoreCursorUsage.html
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CoreDBAdmin.html
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CoreDbCXXUsage.html
(7 KB)
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CoreEnvUsage.html
(6.97 KB)
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Cursors.html
(5.93 KB)
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DBEntry.html
(6.46 KB)
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DBOpenFlags.html
(4.32 KB)
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DbCXXUsage.html
(20.83 KB)
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DeleteEntryWCursor.html
(3.69 KB)
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Positioning.html
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PutEntryWCursor.html
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ReplacingEntryWCursor.html
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accessmethods.html
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btree.html
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cachesize.html
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concepts.html
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coreExceptions.html
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coredbclose.html
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coreindexusage.html
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databaseLimits.html
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databases.html
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dbErrorReporting.html
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dbconfig.html
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environments.html
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gettingStarted.css
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gettingit.html
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index.html
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indexes.html
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introduction.html
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joins.html
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keyCreator.html
(10.23 KB)
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moreinfo.html
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preface.html
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readSecondary.html
(4.95 KB)
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returns.html
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secondaryCursor.html
(5.34 KB)
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secondaryDelete.html
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usingDbt.html
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Editing: secondaryDelete.html
<?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>Deleting Secondary Database Records</title> <link rel="stylesheet" href="gettingStarted.css" type="text/css" /> <meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /> <link rel="start" href="index.html" title="Getting Started with Berkeley DB" /> <link rel="up" href="indexes.html" title="Chapter 5. Secondary Databases" /> <link rel="prev" href="readSecondary.html" title="Reading Secondary Databases" /> <link rel="next" href="secondaryCursor.html" title="Using Cursors with Secondary Databases" /> </head> <body> <div xmlns="" class="navheader"> <div class="libver"> <p>Library Version 11.2.5.3</p> </div> <table width="100%" summary="Navigation header"> <tr> <th colspan="3" align="center">Deleting Secondary Database Records</th> </tr> <tr> <td width="20%" align="left"><a accesskey="p" href="readSecondary.html">Prev</a> </td> <th width="60%" align="center">Chapter 5. Secondary Databases</th> <td width="20%" align="right"> <a accesskey="n" href="secondaryCursor.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="secondaryDelete"></a>Deleting Secondary Database Records</h2> </div> </div> </div> <p> In general, you <span>will</span> not modify a secondary database directly. In order to modify a secondary database, you should modify the primary database and simply allow DB to manage the secondary modifications for you. </p> <p> However, as a convenience, you can delete <span>secondary database</span> records directly. Doing so causes the associated primary key/data pair to be deleted. This in turn causes DB to delete all <span>secondary database</span> records that reference the primary record. </p> <p> You can use the <code class="methodname">Db::del()</code> method to delete a secondary database record. <span>Note that if your <span>secondary database</span> contains duplicate records, then deleting a record from the set of duplicates causes all of the duplicates to be deleted as well. </span> </p> <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"> <h3 class="title">Note</h3> <p> <span> You can delete a secondary database record using the previously described mechanism </span> only if the primary database is opened for write access. </p> </div> <p>For example:</p> <a id="cxx_index7"></a> <pre class="programlisting">#include <db_cxx.h> #include <string.h> ... Db my_database(NULL, 0); // Primary Db my_index(NULL, 0); // Secondary // Open the primary my_database.open(NULL, // Transaction pointer "my_db.db", // On-disk file that holds the database. NULL, // Optional logical database name DB_BTREE, // Database access method DB_CREATE, // Open flags 0); // File mode (using defaults) // Setup the secondary to use sorted duplicates. // This is often desireable for secondary databases. my_index.set_flags(DB_DUPSORT); // Open the secondary my_index.open(NULL, // Transaction pointer "my_secondary.db", // On-disk file that holds the database. NULL, // Optional logical database name DB_BTREE, // Database access method DB_CREATE, // Open flags. 0); // File mode (using defaults) // Now associate the primary and the secondary my_database.associate(NULL, // Txn id &my_index, // Associated secondary database get_sales_rep, // Callback used for key extraction. 0); // Flags // Name to delete char *search_name = "John Doe"; // Get a search key Dbt key(search_name, strlen(search_name) + 1); // Now delete the secondary record. This causes the associated primary // record to be deleted. If any other secondary databases have secondary // records referring to the deleted primary record, then those secondary // records are also deleted. my_index.del(NULL, &key, 0); </pre> </div> <div class="navfooter"> <hr /> <table width="100%" summary="Navigation footer"> <tr> <td width="40%" align="left"><a accesskey="p" href="readSecondary.html">Prev</a> </td> <td width="20%" align="center"> <a accesskey="u" href="indexes.html">Up</a> </td> <td width="40%" align="right"> <a accesskey="n" href="secondaryCursor.html">Next</a></td> </tr> <tr> <td width="40%" align="left" valign="top">Reading Secondary Databases </td> <td width="20%" align="center"> <a accesskey="h" href="index.html">Home</a> </td> <td width="40%" align="right" valign="top"> <span>Using Cursors with Secondary Databases</span> </td> </tr> </table> </div> </body> </html>
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