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<h1><a href="http://wbowam.github.io/django-17shi-yong.html"> Django 1.7试用 </a></h1>
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<p>首先感谢django团队，在这一版本里django自身提供了数据迁移功能——migration</p>
<h3 id="_1">数据迁移<a class="headerlink" href="#_1" title="Permanent link">¶</a></h3>
<p>修改Model后可以在不影响现有数据的前提下重建表结构。 </p>
<h6 id="southsouthdjango">以往的解决方案是South（于是South成为了django必备的，最受欢迎的应用。）<a class="headerlink" href="#southsouthdjango" title="Permanent link">¶</a></h6>
<h4 id="_2">原理<a class="headerlink" href="#_2" title="Permanent link">¶</a></h4>
<p>django的migration功能，类似与South的migration功能。 </p>
<h5 id="_3">开始一个新的项目<a class="headerlink" href="#_3" title="Permanent link">¶</a></h5>
<div class="highlight"><pre><span class="n">django</span><span class="o">-</span><span class="n">admin</span><span class="p">.</span><span class="n">py</span> <span class="n">startproject</span> <span class="n">mysite</span>
<span class="cp">## Create the tables in the database before we can use them.</span>
<span class="n">python</span> <span class="n">manage</span><span class="p">.</span><span class="n">py</span> <span class="n">migrate</span>
<span class="cp">## Create superuser.</span>
<span class="n">python</span> <span class="n">manage</span><span class="p">.</span><span class="n">py</span> <span class="n">createsuperuser</span>
</pre></div>
<h5 id="app">创建app:<a class="headerlink" href="#app" title="Permanent link">¶</a></h5>
<div class="highlight"><pre><span class="n">python</span> <span class="n">manage</span><span class="p">.</span><span class="n">py</span> <span class="n">startapp</span> <span class="n">myblog</span>
<span class="cp">##1.7版django这一步时会创建一个migrations/目录</span>
</pre></div>
<div class="highlight"><pre><span class="cp">##settings.py</span>
<span class="n">INSTALLED_APPS</span> <span class="o">=</span><span class="p">(</span>
<span class="err">####</span>
<span class="err">'</span><span class="n">myblog</span><span class="err">'</span><span class="p">,</span>
<span class="p">)</span>
</pre></div>
<div class="highlight"><pre><span class="cp">##models.py</span>
<span class="n">class</span> <span class="n">Article</span><span class="p">(</span><span class="n">models</span><span class="p">.</span><span class="n">Model</span><span class="p">)</span><span class="o">:</span>
<span class="n">title</span> <span class="o">=</span> <span class="n">models</span><span class="p">.</span><span class="n">CharField</span><span class="p">(</span><span class="n">max_length</span><span class="o">=</span><span class="mi">18</span><span class="p">,</span> <span class="n">null</span><span class="o">=</span><span class="n">True</span><span class="p">)</span>
</pre></div>
<h5 id="_4">生成数据表<a class="headerlink" href="#_4" title="Permanent link">¶</a></h5>
<p>（覆盖了syncdb功能，不过别担心，syncdb仍然还有～） </p>
<div class="highlight"><pre><span class="n">python</span> <span class="n">manage</span><span class="p">.</span><span class="n">py</span> <span class="n">makemigrations</span> <span class="n">myblog</span>
</pre></div>
<p>运行结果如下</p>
<div class="highlight"><pre><span class="n">Migrations</span> <span class="k">for</span> <span class="err">‘</span><span class="n">myblog</span><span class="err">’</span><span class="o">:</span>
<span class="mo">0001</span><span class="n">_initial</span><span class="p">.</span><span class="n">py</span><span class="o">:</span>
<span class="o">-</span> <span class="n">Create</span> <span class="n">model</span> <span class="n">Article</span>
</pre></div>
<p>看看生成了哪些文件</p>
<div class="highlight"><pre><span class="n">ls</span> <span class="n">myblog</span><span class="o">/</span><span class="n">migrations</span><span class="o">/</span>
<span class="n">__init__</span><span class="p">.</span><span class="n">py</span> <span class="mo">0001</span><span class="n">_initial</span><span class="p">.</span><span class="n">py</span>
</pre></div>
<h4 id="modelsauthor">修改models，添加一个author属性<a class="headerlink" href="#modelsauthor" title="Permanent link">¶</a></h4>
<div class="highlight"><pre><span class="n">class</span> <span class="n">Article</span><span class="p">(</span><span class="n">models</span><span class="p">.</span><span class="n">Model</span><span class="p">)</span><span class="o">:</span>
<span class="n">title</span> <span class="o">=</span> <span class="n">models</span><span class="p">.</span><span class="n">CharField</span><span class="p">(</span><span class="n">max_length</span><span class="o">=</span><span class="mi">18</span><span class="p">,</span> <span class="n">null</span><span class="o">=</span><span class="n">True</span><span class="p">)</span>
<span class="n">author</span> <span class="o">=</span> <span class="n">models</span><span class="p">.</span><span class="n">OneToOneField</span><span class="p">(</span><span class="n">User</span><span class="p">,</span> <span class="n">null</span><span class="o">=</span><span class="n">True</span><span class="p">)</span>
</pre></div>
<h5 id="_5">生成数据表（修改后）<a class="headerlink" href="#_5" title="Permanent link">¶</a></h5>
<div class="highlight"><pre><span class="n">python</span> <span class="n">manage</span><span class="p">.</span><span class="n">py</span> <span class="n">makemigrations</span> <span class="n">myblog</span>
<span class="cp">##运行结果</span>
<span class="n">Migrations</span> <span class="k">for</span> <span class="err">‘</span><span class="n">myblog</span><span class="err">’</span><span class="o">:</span>
<span class="mo">0002</span><span class="n">_article_author</span><span class="p">.</span><span class="n">py</span><span class="o">:</span>
<span class="o">-</span> <span class="n">Add</span> <span class="n">field</span> <span class="n">author</span> <span class="n">to</span> <span class="n">article</span>
</pre></div>
<p>我们来看看他重新生成数据表时干了些什么
<em> 从上一个migration中获取之前的Model列表，写到set中.
</em> 获取现有的model列表，写入set中。
* 遍历这两个set的差集，获取差集Model中所有的field，如果field的定义相同，就询问用户是否是一个rename的model，否则视为创建。</p>
<h4 id="migrate">数据迁移（migrate）<a class="headerlink" href="#migrate" title="Permanent link">¶</a></h4>
<p><code>python manage.py migrate myblog</code> </p>
<hr />
<p>That's all
以上是个人对migration的理解，求纠错和指点～～</p>
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<h4>Published</h4>
<time pubdate="pubdate" datetime="2014-09-07T00:00:00+08:00">Sep 7, 2014</time>
<h4>Category</h4>
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