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    <p>Two things about your question:</p> <p>1) The example in the cookbook might be a bit too complex for what you're trying to do. Here is a simpler one:</p> <p>Given a document structure that looks like this:</p> <pre><code>{ "url" : "http://example.com/page8580.html", "user_id" : "Jonathan.Clark", "date" : ISODate("2012-06-11T10:59:36.271Z") } </code></pre> <p>Here is some sample JavaScript code to run a map/reduce job that will count the number of visits per distinct URL.</p> <pre><code>// Map function: map = function() { emit({ url: this.url }, {count: 1}); } // Reduce function: reduce = function(key, values) { var count = 0; values.forEach( function(val) { count += val['count']; } ); return {count: count}; }; // Run the Map/Reduce function across the 'pageviews' collection: // Note that MongoDB will store the results in the 'pages_per_day' // collection because the 'out' parameter is present db.pageviews.mapReduce( map, // pass in the 'map' function as an argument reduce, // pass in the 'reduce' function as an argument // options { out: 'pages_per_day', // output collection verbose: true } // report extra statistics ); </code></pre> <p>2) If you want to run the Map/Reduce function on only a subset of the 'pageviews' collection, you can specify a query to the call to 'mapReduce()' in order to restrict the number of documents that the 'map()' function will operate on:</p> <pre><code>// Run the Map/Reduce function across the 'pageviews' collection, but // only report on the pages seen by "Jonathan.Clark" db.pageviews.mapReduce( map, // Use the same map &amp; reduce functions as before reduce, { out: 'pages_per_day_1user', // output to different collection query:{ 'user_id': "Jonathan.Clark" } // query descriptor verbose: true } ); </code></pre> <p>Note that if you aren't using JavaScript, you'll have to translate these calls into whatever programming language you're using.</p> <p>3) Here's an example of calling the Map/Reduce function with a query condition using PHP:</p> <pre><code>$outer = $this-&gt;cimongo-&gt;command (array ( "mapreduce" =&gt; "pageviews", "map" =&gt; $map, "reduce" =&gt; $reduce, "out" =&gt; "pages_per_day_1user", "query" =&gt; array( "user_id" =&gt; "Jonathan.Clark" ) )); </code></pre> <p>4) For more information about Map/Reduce, see the following references:</p> <ul> <li>Map/Reduce Manual page: <a href="http://www.mongodb.org/display/DOCS/MapReduce" rel="noreferrer">http://www.mongodb.org/display/DOCS/MapReduce</a></li> <li>Debugging Map/Reduce: <a href="http://www.mongodb.org/display/DOCS/Troubleshooting+MapReduce" rel="noreferrer">http://www.mongodb.org/display/DOCS/Troubleshooting+MapReduce</a></li> <li><p>Using Map/Reduce in PHP: <a href="http://us.php.net/manual/en/mongodb.command.php" rel="noreferrer">http://us.php.net/manual/en/mongodb.command.php</a></p> <p>--William </p></li> </ul>
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    1. COThe query param is what i am looking for, however is it possible to query an array of values? for example in find() I use something like _id : { $in : [1,2,3,4] }
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    2. COThe 'query' parameter contains a document that describes an arbitrary MongoDB query; you can use any valid syntax you like in that field.
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