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Derek Allardd2df9bc2007-04-15 17:41:17 +0000[diff] [blame]5<title>CodeIgniter User Guide</title>
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Derek Allard60ca9b72007-07-12 19:53:27 +0000[diff] [blame]36<td><h1>CodeIgniter User Guide Version 1.5.4</h1></td>
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Derek Allardd2df9bc2007-04-15 17:41:17 +0000[diff] [blame]49<a href="http://www.codeigniter.com/">CodeIgniter Home</a> &nbsp;&#8250;&nbsp;
adminfb28bb82006-09-24 17:59:33 +0000[diff] [blame]50<a href="../index.html">User Guide Home</a> &nbsp;&#8250;&nbsp;
51<a href="index.html">Database Library</a> &nbsp;&#8250;&nbsp;
52Transactions
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66
67<h1>Transactions</h1>
68
Derek Allardd2df9bc2007-04-15 17:41:17 +0000[diff] [blame]69<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
admina33ec0a2006-10-10 23:38:05 +0000[diff] [blame]70to be running InnoDB or BDB table types rather then the more common MyISAM. Most other database platforms support transactions natively.</p>
adminfb28bb82006-09-24 17:59:33 +0000[diff] [blame]71
admine334c472006-10-21 19:44:22 +0000[diff] [blame]72<p>If you are not familiar with
73transactions we recommend you find a good online resource to learn about them for your particular database. The information below assumes you
admina33ec0a2006-10-10 23:38:05 +0000[diff] [blame]74have a basic understanding of transactions.
adminfb28bb82006-09-24 17:59:33 +0000[diff] [blame]75</p>
76
Derek Allardd2df9bc2007-04-15 17:41:17 +0000[diff] [blame]77<h2>CodeIgniter's Approach to Transactions</h2>
adminfb28bb82006-09-24 17:59:33 +0000[diff] [blame]78
Derek Allardd2df9bc2007-04-15 17:41:17 +0000[diff] [blame]79<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
adminfb28bb82006-09-24 17:59:33 +0000[diff] [blame]80because it greatly simplifies the process of running transactions. In most cases all that is required are two lines of code.</p>
81
admind125c5c2006-09-25 23:26:12 +0000[diff] [blame]82<p>Traditionally, transactions have required a fair amount of work to implement since they demand that you to keep track of your queries
admine334c472006-10-21 19:44:22 +0000[diff] [blame]83and determine whether to <dfn>commit</dfn> or <dfn>rollback</dfn> based on the success or failure of your queries. This is particularly cumbersome with
admind125c5c2006-09-25 23:26:12 +0000[diff] [blame]84nested queries. In contrast,
85we've implemented a smart transaction system that does all this for you automatically (you can also manage your transactions manually if you choose to,
86but there's really no benefit).</p>
adminfb28bb82006-09-24 17:59:33 +0000[diff] [blame]87
88<h2>Running Transactions</h2>
89
90<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>
91
92<code>
93<kbd>$this->db->trans_start();</kbd><br />
94$this->db->query('AN SQL QUERY...');<br />
95$this->db->query('ANOTHER QUERY...');<br />
96$this->db->query('AND YET ANOTHER QUERY...');<br />
97<kbd>$this->db->trans_complete();</kbd>
98</code>
99
admind125c5c2006-09-25 23:26:12 +0000[diff] [blame]100<p>You can run as many queries as you want between the start/complete functions and they will all be committed or rolled back based on success or failure
101of any given query.</p>
adminfb28bb82006-09-24 17:59:33 +0000[diff] [blame]102
103
104<h2>Managing Errors</h2>
105
106<p>If you have error reporting enabled in your <dfn>config/database.php</dfn> file you'll see a standard error message if the commit was unsuccessful. If debugging is turned off, you can
107manage your own errors like this:</p>
108
109<code>
110$this->db->trans_start();<br />
111$this->db->query('AN SQL QUERY...');<br />
112$this->db->query('ANOTHER QUERY...');<br />
113$this->db->trans_complete();<br />
114<br />
115if (<kbd>$this->db->trans_status()</kbd> === FALSE)<br />
116{<br />
admind125c5c2006-09-25 23:26:12 +0000[diff] [blame]117&nbsp;&nbsp;&nbsp;&nbsp;// generate an error... or use the log_message() function to log your error<br />
adminfb28bb82006-09-24 17:59:33 +0000[diff] [blame]118}
119</code>
120
121
122<h2>Enabling Transactions</h2>
123
124<p>Transactions are enabled automatically the moment you use <dfn>$this->db->trans_start()</dfn>. If you would like to disable transactions you
Derek Allardc6441282007-07-04 23:54:32 +0000[diff] [blame]125can do so using <dfn>$this->db->trans_off()</dfn>:</p>
adminfb28bb82006-09-24 17:59:33 +0000[diff] [blame]126
127<code>
128<kbd>$this->db->trans_off()</kbd><br /><br />
129
130$this->db->trans_start();<br />
131$this->db->query('AN SQL QUERY...');<br />
132$this->db->trans_complete();
133</code>
134
135<p class="important">When transactions are disabled, your queries will be auto-commited, just as they are when running queries without transactions.</p>
136
137
138<h2>Test Mode</h2>
139
140<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.
Derek Allardc6441282007-07-04 23:54:32 +0000[diff] [blame]141To use test mode simply set the first parameter in the <dfn>$this->db->trans_start()</dfn> function to <samp>TRUE</samp>:</p>
adminfb28bb82006-09-24 17:59:33 +0000[diff] [blame]142
143<code>
144$this->db->trans_start(<samp>TRUE</samp>); // Query will be rolled back<br />
145$this->db->query('AN SQL QUERY...');<br />
146$this->db->trans_complete();
147</code>
148
149
150<h2>Running Transactions Manually</h2>
151
152<p>If you would like to run transactions manually you can do so as follows:</p>
153
154<code>
155$this->db->trans_begin();<br /><br />
156
157$this->db->query('AN SQL QUERY...');<br />
158$this->db->query('ANOTHER QUERY...');<br />
159$this->db->query('AND YET ANOTHER QUERY...');<br />
160
161<br />
162
163if ($this->db->trans_status() === FALSE)<br />
164{<br />
165&nbsp;&nbsp;&nbsp;&nbsp;$this->db->trans_rollback();<br />
166}<br />
167else<br />
168{<br />
169&nbsp;&nbsp;&nbsp;&nbsp;$this->db->trans_commit();<br />
170}<br />
171</code>
172
173<p class="important"><strong>Note:</strong> Make sure to use <kbd>$this->db->trans_begin()</kbd> when running manual transactions, <strong>NOT</strong>
174<dfn>$this->db->trans_start()</dfn>.</p>
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