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| <h1>Transactions</h1> | |
| <p>CodeIgniter's database abstraction allows you to use <dfn>transactions</dfn> with databases that support transaction-safe table types. In MySQL, you'll need | |
| to be running InnoDB or BDB table types rather then the more common MyISAM. Most other database platforms support transactions natively.</p> | |
| <p>If you are not familiar with | |
| transactions we recommend you find a good online resource to learn about them for your particular database. The information below assumes you | |
| have a basic understanding of transactions. | |
| </p> | |
| <h2>CodeIgniter's Approach to Transactions</h2> | |
| <p>CodeIgniter utilizes an approach to transactions that is very similar to the process used by the popular database class ADODB. We've chosen that approach | |
| because it greatly simplifies the process of running transactions. In most cases all that is required are two lines of code.</p> | |
| <p>Traditionally, transactions have required a fair amount of work to implement since they demand that you to keep track of your queries | |
| and determine whether to <dfn>commit</dfn> or <dfn>rollback</dfn> based on the success or failure of your queries. This is particularly cumbersome with | |
| nested queries. In contrast, | |
| we've implemented a smart transaction system that does all this for you automatically (you can also manage your transactions manually if you choose to, | |
| but there's really no benefit).</p> | |
| <h2>Running Transactions</h2> | |
| <p>To run your queries using transactions you will use the <dfn>$this->db->trans_start()</dfn> and <dfn>$this->db->trans_complete()</dfn> functions as follows:</p> | |
| <code> | |
| <kbd>$this->db->trans_start();</kbd><br /> | |
| $this->db->query('AN SQL QUERY...');<br /> | |
| $this->db->query('ANOTHER QUERY...');<br /> | |
| $this->db->query('AND YET ANOTHER QUERY...');<br /> | |
| <kbd>$this->db->trans_complete();</kbd> | |
| </code> | |
| <p>You can run as many queries as you want between the start/complete functions and they will all be committed or rolled back based on success or failure | |
| of any given query.</p> | |
| <h2>Managing Errors</h2> | |
| <p>If you have error reporting enabled in your <dfn>config/database.php</dfn> file you'll see a standard error message if the commit was unsuccessful. If debugging is turned off, you can | |
| manage your own errors like this:</p> | |
| <code> | |
| $this->db->trans_start();<br /> | |
| $this->db->query('AN SQL QUERY...');<br /> | |
| $this->db->query('ANOTHER QUERY...');<br /> | |
| $this->db->trans_complete();<br /> | |
| <br /> | |
| if (<kbd>$this->db->trans_status()</kbd> === FALSE)<br /> | |
| {<br /> | |
| // generate an error... or use the log_message() function to log your error<br /> | |
| } | |
| </code> | |
| <h2>Enabling Transactions</h2> | |
| <p>Transactions are enabled automatically the moment you use <dfn>$this->db->trans_start()</dfn>. If you would like to disable transactions you | |
| can do so using <dfn>$this->db->trans_off()</dfn>:</p> | |
| <code> | |
| <kbd>$this->db->trans_off()</kbd><br /><br /> | |
| $this->db->trans_start();<br /> | |
| $this->db->query('AN SQL QUERY...');<br /> | |
| $this->db->trans_complete(); | |
| </code> | |
| <p class="important">When transactions are disabled, your queries will be auto-commited, just as they are when running queries without transactions.</p> | |
| <h2>Test Mode</h2> | |
| <p>You can optionally put the transaction system into "test mode", which will cause your queries to be rolled back -- even if the queries produce a valid result. | |
| To use test mode simply set the first parameter in the <dfn>$this->db->trans_start()</dfn> function to <samp>TRUE</samp>:</p> | |
| <code> | |
| $this->db->trans_start(<samp>TRUE</samp>); // Query will be rolled back<br /> | |
| $this->db->query('AN SQL QUERY...');<br /> | |
| $this->db->trans_complete(); | |
| </code> | |
| <h2>Running Transactions Manually</h2> | |
| <p>If you would like to run transactions manually you can do so as follows:</p> | |
| <code> | |
| $this->db->trans_begin();<br /><br /> | |
| $this->db->query('AN SQL QUERY...');<br /> | |
| $this->db->query('ANOTHER QUERY...');<br /> | |
| $this->db->query('AND YET ANOTHER QUERY...');<br /> | |
| <br /> | |
| if ($this->db->trans_status() === FALSE)<br /> | |
| {<br /> | |
| $this->db->trans_rollback();<br /> | |
| }<br /> | |
| else<br /> | |
| {<br /> | |
| $this->db->trans_commit();<br /> | |
| }<br /> | |
| </code> | |
| <p class="important"><strong>Note:</strong> Make sure to use <kbd>$this->db->trans_begin()</kbd> when running manual transactions, <strong>NOT</strong> | |
| <dfn>$this->db->trans_start()</dfn>.</p> | |
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