title: insert or ignore multiple documents in mongoDB
body: <p>I have a collection in which all of my documents have at least these 2 fields, say <code>name</code> and <code>url</code> (where <code>url</code> is unique so I set up a unique index on it).  Now if I try to insert a document with a duplicate <code>url</code>, it will give an error and halt the program.  I don't want this behavior, but I need something like <code>mysql</code>'s <code>insert or ignore</code>, so that mongoDB should not insert the document with duplicate <code>url</code> and continue with the next documents.  </p>
  
  <p>Is there some parameter I can pass to the <code>insert</code> command to achieve this behavior? I generally do a batch of inserts using <code>pymongo</code> as:</p>
  
  <pre><code>collection.insert(document_array)
  </code></pre>
  
  <p>Here <code>collection</code> is a collection and <code>document_array</code> is an array of documents.</p>
  
  <p>So is there some way I can implement the <code>insert or ignore</code> functionality for a multiple document insert?</p>