docs/gsg_txn/C/txnindices.html

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   6     <title>Secondary Indices with Transaction Applications</title>
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  17         <p>Library Version 11.2.5.3</p>
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  21           <th colspan="3" align="center">Secondary Indices with Transaction Applications</th>
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  23         <tr>
  24           <td width="20%" align="left"><a accesskey="p" href="txncursor.html">Prev</a> </td>
  25           <th width="60%" align="center">Chapter 3. Transaction Basics</th>
  26           <td width="20%" align="right"> <a accesskey="n" href="maxtxns.html">Next</a></td>
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  34           <div>
  35             <h2 class="title" style="clear: both"><a id="txnindices"></a>Secondary Indices with Transaction Applications</h2>
  36           </div>
  37         </div>
  38       </div>
  39       <p>
  40             You can use transactions with your secondary indices so long as you
  41
  42             <span>
  43                 open the secondary index so that it supports transactions (that is,
  44                 you wrap the database open in a transaction, or use auto commit,
  45                 in the same way as when you open a primary transactional database).
  46             </span>
  47
  48
  49
  50             <span>
  51                 In addition, you must make sure that when you associate the
  52                 secondary index with the primary database, the association is
  53                 performed using a transaction. The easiest thing to do here is
  54                 to simply specify <code class="literal">DB_AUTO_COMMIT</code> when you
  55                 perform the association.
  56             </span>
  57         </p>
  58       <p>
  59             All other aspects of using secondary indices with transactions are
  60             identical to using secondary indices without transactions. In
  61             addition, transaction-protecting
  62                 <span>
  63                     cursors opened against secondary indices is performed in
  64                     exactly the same way as when you use transactional cursors
  65                     against a primary database.
  66                 </span>
  67
  68                     See <a class="xref" href="txncursor.html" title="Transactional Cursors">Transactional Cursors</a> for details.
  69         </p>
  70       <p>
  71             Note that when you use transactions to protect your database writes, your secondary indices are protected from
  72             corruption because updates to the primary and the secondaries are performed in a single atomic transaction.
  73         </p>
  74       <p>
  75             For example:
  76         </p>
  77       <pre class="programlisting">#include &lt;db.h&gt;
  78
  79 ...
  80
  81 DB_ENV *envp;      /* Environment pointer */
  82 DB *dbp, *sdbp;    /* Primary and secondary DB handles */
  83 u_int32_t flags;   /* Primary database open flags */
  84 int ret;           /* Function return value */
  85
  86 /* Environment and primary database opens omitted */
  87
  88 /* Secondary */
  89 ret = db_create(&amp;sdbp, envp, 0);
  90 if (ret != 0) {
  91   /* Error handling goes here */
  92 }
  93 /* open the secondary database */
  94 ret = sdbp-&gt;open(sdbp,          /* DB structure pointer */
  95                  NULL,            /* Transaction pointer */
  96                  "my_secdb.db",   /* On-disk file that holds the
  97                                    * database. */
  98                  NULL,            /* Optional logical database name */
  99                  DB_BTREE,        /* Database access method */
 100                  DB_AUTO_COMMIT,  /* Open flags */
 101                  0);              /* File mode (using defaults) */
 102 if (ret != 0) {
 103   /* Error handling goes here */
 104 }
 105
 106 /* Now associate the secondary to the primary */
 107 dbp-&gt;associate(dbp,            /* Primary database */
 108                NULL,           /* TXN id */
 109                sdbp,           /* Secondary database */
 110                get_sales_rep,  /* Callback used for key creation. This
 111                                 * is described in the Getting Started
 112                                 * guide. */
 113                DB_AUTO_COMMIT);/* Flags */</pre>
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 121             <a accesskey="u" href="usingtxns.html">Up</a>
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