MongoDB PHP Map Reduces db Approval Error

Question

My first go to map / shrinking using PHP / MongoDB. I got stuck with an error while running the MapReduce command.

My code is:

$map = "function () {". "emit(this.topic_id, {re_date:this.date_posted}); " . "}"; $reduce = "function (key, values) {" . "var result = {last_post: 0};" . "var max = ISODate('1970-01-01T00:00:00Z');" . "values.forEach(function (value) {" . "if (max == ISODate('1970-01-01T00:00:00Z')) {" . "max = value.re_date;}" . "if (max < value.re_date) {max = value.re_date;}});" . "result.last_post = max;" . "return result;" . "}"; $mapFunc = new MongoCode($map); $reduceFunc = new MongoCode($reduce); $collection = new MongoCollection($db, 'posts'); $command = array( 'mapreduce' => $collection, 'map' => $mapFunc, 'reduce' => $reduceFunc, "query" => array("topic_id" => "2116"), "out" => array("merge" => "eventCounts")); $threadInfo = $db->command($command); $threadsCollection = $db->selectCollection($threadInfo['result']); $stats = $statsCollection->find(); foreach ($stats as $stat) { echo $stats['_id'] .' Visited '; foreach ($stats['value']['types'] as $type => $times) { echo "Type $type $times Times, "; } foreach ($stats['value']['tags'] as $tag => $times) { echo "Tag $tag $times Times, "; } echo "\n"; } 

When I run the command, I return an error:

invalid type assertion for field (mapreduce) 3! = 2 assertionCode 13111
Errmsg db approval error
ok 0

I closely followed the example here , so I'm not sure what is going wrong. Any suggestions appreciated.

Answer 1

It is important to remember that when using mapReduce (), the return value of the reduce () function should be the same form as the one you expect to receive in the "values" element of the reduce () function and this, in turn, should be the same. like the emit () function.

For a collection containing documents of the following type:

 > db.posts.count(); 1000 > db.posts.findOne(); { "_id" : 0, "date_posted" : ISODate("2012-04-04T05:54:44.535Z"), "topic_id" : "sierra" } 

The following code will produce the desired result:

 <?php $conn = new Mongo("localhost:$port"); $db = $conn->test; $collection = $db->tst; $map = new MongoCode( "function() { emit( this.topic_id, { last_post: this.date_posted } ); }" ); $reduce = new MongoCode( "function(key, values) { ". "var max = ISODate('1970-01-01T00:00:00Z'); ". "values.forEach(function(val) { ". "if ( max < val.last_post ) max = val.last_post; ". "}); ". "return {last_post : max}; " . "}" ); $result = $db->command( array( "mapreduce" => "posts", "map" => $map, "reduce" => $reduce, "query" => array( "topic_id" => "alpha"), "out" => array( "merge" => "lastPosts") ) ); echo "result: "; print_r($result); $collection = $db->lastPosts; $cursor = $collection->find()->limit(6); date_default_timezone_set("UTC"); foreach( $cursor as $doc ) { $date = date( "r", $doc['value']['last_post']->sec ); echo $doc['_id'] . " last visited at " . $date ."\n" ; } ?>