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<div class="section" id="migrations-class">
<h1>Migrations Class<a class="headerlink" href="#migrations-class" title="Permalink to this headline">¶</a></h1>
<p>Migrations are a convenient way for you to alter your database in a
structured and organized manner. You could edit fragments of SQL by hand
but you would then be responsible for telling other developers that they
need to go and run them. You would also have to keep track of which changes
need to be run against the production machines next time you deploy.</p>
<p>The database table <strong>migration</strong> tracks which migrations have already been
run so all you have to do is update your application files and
call <code class="docutils literal"><span class="pre">$this->migration->current()</span></code> to work out which migrations should be run.
The current version is found in <strong>application/config/migration.php</strong>.</p>
<div class="contents local topic" id="contents">
<ul class="simple">
<li><a class="reference internal" href="#migration-file-names" id="id1">Migration file names</a></li>
<li><a class="reference internal" href="#create-a-migration" id="id2">Create a Migration</a></li>
<li><a class="reference internal" href="#usage-example" id="id3">Usage Example</a></li>
<li><a class="reference internal" href="#migration-preferences" id="id4">Migration Preferences</a></li>
<li><a class="reference internal" href="#class-reference" id="id5">Class Reference</a></li>
</ul>
</div>
<div class="custom-index container"></div><div class="section" id="migration-file-names">
<h2><a class="toc-backref" href="#id1">Migration file names</a><a class="headerlink" href="#migration-file-names" title="Permalink to this headline">¶</a></h2>
<p>Each Migration is run in numeric order forward or backwards depending on the
method taken. Two numbering styles are available:</p>
<ul class="simple">
<li><strong>Sequential:</strong> each migration is numbered in sequence, starting with <strong>001</strong>.
Each number must be three digits, and there must not be any gaps in the
sequence. (This was the numbering scheme prior to CodeIgniter 3.0.)</li>
<li><strong>Timestamp:</strong> each migration is numbered using the timestamp when the migration
was created, in <strong>YYYYMMDDHHIISS</strong> format (e.g. <strong>20121031100537</strong>). This
helps prevent numbering conflicts when working in a team environment, and is
the preferred scheme in CodeIgniter 3.0 and later.</li>
</ul>
<p>The desired style may be selected using the <code class="docutils literal"><span class="pre">$config['migration_type']</span></code>
setting in your <em>application/config/migration.php</em> file.</p>
<p>Regardless of which numbering style you choose to use, prefix your migration
files with the migration number followed by an underscore and a descriptive
name for the migration. For example:</p>
<ul class="simple">
<li>001_add_blog.php (sequential numbering)</li>
<li>20121031100537_add_blog.php (timestamp numbering)</li>
</ul>
</div>
<div class="section" id="create-a-migration">
<h2><a class="toc-backref" href="#id2">Create a Migration</a><a class="headerlink" href="#create-a-migration" title="Permalink to this headline">¶</a></h2>
<p>This will be the first migration for a new site which has a blog. All
migrations go in the <strong>application/migrations/</strong> directory and have names such
as <em>20121031100537_add_blog.php</em>.</p>
<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="o"><?</span><span class="nx">php</span>
<span class="nb">defined</span><span class="p">(</span><span class="s1">'BASEPATH'</span><span class="p">)</span> <span class="k">OR</span> <span class="k">exit</span><span class="p">(</span><span class="s1">'No direct script access allowed'</span><span class="p">);</span>
<span class="k">class</span> <span class="nc">Migration_Add_blog</span> <span class="k">extends</span> <span class="nx">CI_Migration</span> <span class="p">{</span>
<span class="k">public</span> <span class="k">function</span> <span class="nf">up</span><span class="p">()</span>
<span class="p">{</span>
<span class="nv">$this</span><span class="o">-></span><span class="na">dbforge</span><span class="o">-></span><span class="na">add_field</span><span class="p">(</span><span class="k">array</span><span class="p">(</span>
<span class="s1">'blog_id'</span> <span class="o">=></span> <span class="k">array</span><span class="p">(</span>
<span class="s1">'type'</span> <span class="o">=></span> <span class="s1">'INT'</span><span class="p">,</span>
<span class="s1">'constraint'</span> <span class="o">=></span> <span class="mi">5</span><span class="p">,</span>
<span class="s1">'unsigned'</span> <span class="o">=></span> <span class="k">TRUE</span><span class="p">,</span>
<span class="s1">'auto_increment'</span> <span class="o">=></span> <span class="k">TRUE</span>
<span class="p">),</span>
<span class="s1">'blog_title'</span> <span class="o">=></span> <span class="k">array</span><span class="p">(</span>
<span class="s1">'type'</span> <span class="o">=></span> <span class="s1">'VARCHAR'</span><span class="p">,</span>
<span class="s1">'constraint'</span> <span class="o">=></span> <span class="s1">'100'</span><span class="p">,</span>
<span class="p">),</span>
<span class="s1">'blog_description'</span> <span class="o">=></span> <span class="k">array</span><span class="p">(</span>
<span class="s1">'type'</span> <span class="o">=></span> <span class="s1">'TEXT'</span><span class="p">,</span>
<span class="s1">'null'</span> <span class="o">=></span> <span class="k">TRUE</span><span class="p">,</span>
<span class="p">),</span>
<span class="p">));</span>
<span class="nv">$this</span><span class="o">-></span><span class="na">dbforge</span><span class="o">-></span><span class="na">add_key</span><span class="p">(</span><span class="s1">'blog_id'</span><span class="p">,</span> <span class="k">TRUE</span><span class="p">);</span>
<span class="nv">$this</span><span class="o">-></span><span class="na">dbforge</span><span class="o">-></span><span class="na">create_table</span><span class="p">(</span><span class="s1">'blog'</span><span class="p">);</span>
<span class="p">}</span>
<span class="k">public</span> <span class="k">function</span> <span class="nf">down</span><span class="p">()</span>
<span class="p">{</span>
<span class="nv">$this</span><span class="o">-></span><span class="na">dbforge</span><span class="o">-></span><span class="na">drop_table</span><span class="p">(</span><span class="s1">'blog'</span><span class="p">);</span>
<span class="p">}</span>
<span class="p">}</span>
</pre></div>
</div>
<p>Then in <strong>application/config/migration.php</strong> set <code class="docutils literal"><span class="pre">$config['migration_version']</span> <span class="pre">=</span> <span class="pre">20121031100537;</span></code>.</p>
</div>
<div class="section" id="usage-example">
<h2><a class="toc-backref" href="#id3">Usage Example</a><a class="headerlink" href="#usage-example" title="Permalink to this headline">¶</a></h2>
<p>In this example some simple code is placed in <strong>application/controllers/Migrate.php</strong>
to update the schema.:</p>
<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="o"><?</span><span class="nx">php</span>
<span class="k">class</span> <span class="nc">Migrate</span> <span class="k">extends</span> <span class="nx">CI_Controller</span>
<span class="p">{</span>
<span class="k">public</span> <span class="k">function</span> <span class="nf">index</span><span class="p">()</span>
<span class="p">{</span>
<span class="nv">$this</span><span class="o">-></span><span class="na">load</span><span class="o">-></span><span class="na">library</span><span class="p">(</span><span class="s1">'migration'</span><span class="p">);</span>
<span class="k">if</span> <span class="p">(</span><span class="nv">$this</span><span class="o">-></span><span class="na">migration</span><span class="o">-></span><span class="na">current</span><span class="p">()</span> <span class="o">===</span> <span class="k">FALSE</span><span class="p">)</span>
<span class="p">{</span>
<span class="nx">show_error</span><span class="p">(</span><span class="nv">$this</span><span class="o">-></span><span class="na">migration</span><span class="o">-></span><span class="na">error_string</span><span class="p">());</span>
<span class="p">}</span>
<span class="p">}</span>
<span class="p">}</span>
</pre></div>
</div>
</div>
<div class="section" id="migration-preferences">
<h2><a class="toc-backref" href="#id4">Migration Preferences</a><a class="headerlink" href="#migration-preferences" title="Permalink to this headline">¶</a></h2>
<p>The following is a table of all the config options for migrations.</p>
<table border="1" class="docutils">
<colgroup>
<col width="22%" />
<col width="18%" />
<col width="22%" />
<col width="38%" />
</colgroup>
<thead valign="bottom">
<tr class="row-odd"><th class="head">Preference</th>
<th class="head">Default</th>
<th class="head">Options</th>
<th class="head">Description</th>
</tr>
</thead>
<tbody valign="top">
<tr class="row-even"><td><strong>migration_enabled</strong></td>
<td>FALSE</td>
<td>TRUE / FALSE</td>
<td>Enable or disable migrations.</td>
</tr>
<tr class="row-odd"><td><strong>migration_path</strong></td>
<td>APPPATH.’migrations/’</td>
<td>None</td>
<td>The path to your migrations folder.</td>
</tr>
<tr class="row-even"><td><strong>migration_version</strong></td>
<td>0</td>
<td>None</td>
<td>The current version your database should use.</td>
</tr>
<tr class="row-odd"><td><strong>migration_table</strong></td>
<td>migrations</td>
<td>None</td>
<td>The table name for storing the schema
version number.</td>
</tr>
<tr class="row-even"><td><strong>migration_auto_latest</strong></td>
<td>FALSE</td>
<td>TRUE / FALSE</td>
<td>Enable or disable automatically
running migrations.</td>
</tr>
<tr class="row-odd"><td><strong>migration_type</strong></td>
<td>‘timestamp’</td>
<td>‘timestamp’ / ‘sequential’</td>
<td>The type of numeric identifier used to name
migration files.</td>
</tr>
</tbody>
</table>
</div>
<div class="section" id="class-reference">
<h2><a class="toc-backref" href="#id5">Class Reference</a><a class="headerlink" href="#class-reference" title="Permalink to this headline">¶</a></h2>
<dl class="class">
<dt id="CI_Migration">
<em class="property">class </em><code class="descname">CI_Migration</code><a class="headerlink" href="#CI_Migration" title="Permalink to this definition">¶</a></dt>
<dd><dl class="method">
<dt id="CI_Migration::current">
<code class="descname">current</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#CI_Migration::current" title="Permalink to this definition">¶</a></dt>
<dd><table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Returns:</th><td class="field-body">TRUE if no migrations are found, current version string on success, FALSE on failure</td>
</tr>
<tr class="field-even field"><th class="field-name">Return type:</th><td class="field-body">mixed</td>
</tr>
</tbody>
</table>
<p>Migrates up to the current version (whatever is set for
<code class="docutils literal"><span class="pre">$config['migration_version']</span></code> in <em>application/config/migration.php</em>).</p>
</dd></dl>
<dl class="method">
<dt id="CI_Migration::error_string">
<code class="descname">error_string</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#CI_Migration::error_string" title="Permalink to this definition">¶</a></dt>
<dd><table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Returns:</th><td class="field-body">Error messages</td>
</tr>
<tr class="field-even field"><th class="field-name">Return type:</th><td class="field-body">string</td>
</tr>
</tbody>
</table>
<p>This returns a string of errors that were detected while performing a migration.</p>
</dd></dl>
<dl class="method">
<dt id="CI_Migration::find_migrations">
<code class="descname">find_migrations</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#CI_Migration::find_migrations" title="Permalink to this definition">¶</a></dt>
<dd><table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Returns:</th><td class="field-body">An array of migration files</td>
</tr>
<tr class="field-even field"><th class="field-name">Return type:</th><td class="field-body">array</td>
</tr>
</tbody>
</table>
<p>An array of migration filenames are returned that are found in the <strong>migration_path</strong> property.</p>
</dd></dl>
<dl class="method">
<dt id="CI_Migration::latest">
<code class="descname">latest</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#CI_Migration::latest" title="Permalink to this definition">¶</a></dt>
<dd><table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Returns:</th><td class="field-body">Current version string on success, FALSE on failure</td>
</tr>
<tr class="field-even field"><th class="field-name">Return type:</th><td class="field-body">mixed</td>
</tr>
</tbody>
</table>
<p>This works much the same way as <code class="docutils literal"><span class="pre">current()</span></code> but instead of looking for
the <code class="docutils literal"><span class="pre">$config['migration_version']</span></code> the Migration class will use the very
newest migration found in the filesystem.</p>
</dd></dl>
<dl class="method">
<dt id="CI_Migration::version">
<code class="descname">version</code><span class="sig-paren">(</span><em>$target_version</em><span class="sig-paren">)</span><a class="headerlink" href="#CI_Migration::version" title="Permalink to this definition">¶</a></dt>
<dd><table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><ul class="first simple">
<li><strong>$target_version</strong> (<em>mixed</em>) – Migration version to process</li>
</ul>
</td>
</tr>
<tr class="field-even field"><th class="field-name">Returns:</th><td class="field-body"><p class="first">TRUE if no migrations are found, current version string on success, FALSE on failure</p>
</td>
</tr>
<tr class="field-odd field"><th class="field-name">Return type:</th><td class="field-body"><p class="first last">mixed</p>
</td>
</tr>
</tbody>
</table>
<p>Version can be used to roll back changes or step forwards programmatically to
specific versions. It works just like <code class="docutils literal"><span class="pre">current()</span></code> but ignores <code class="docutils literal"><span class="pre">$config['migration_version']</span></code>.</p>
<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$this</span><span class="o">-></span><span class="na">migration</span><span class="o">-></span><span class="na">version</span><span class="p">(</span><span class="mi">5</span><span class="p">);</span>
</pre></div>
</div>
</dd></dl>
</dd></dl>
</div>
</div>
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