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    <p>Your map function takes one parameter: <code>number</code>, which, when called by map-reduce, will be set to null and after coertion (and some <code>%</code> by zero) will make the date your map is returning <code>ISODate("0NaN-NaN-NaNTNaN:NaN:NaNZ")</code>. This after type conversion becomes <code>datetime.datetime(1970, 1, 1, 0, 0)</code>.</p> <p>Remove the parameter and it should work.</p> <p><strong>edit</strong></p> <p>To confirm that, try running this code:</p> <pre><code>from pymongo import Connection from bson.code import Code db = Connection().mr_test for i in xrange(10): db.things.insert({"x" : i}) map = Code("function(number) {" "emit({" "ts : number" "}, 1);" "}") reduce = Code("function(key, vals) {" "var sum = 0;" "for (var i in vals) {" "sum += vals[i]" "}" "return sum;" "}") result = db.things.map_reduce(map, reduce, "test_results") for doc in result.find(): print doc </code></pre> <p>The result on my machine is :</p> <pre><code>{u'_id': {u'ts': None}, u'value': 10.0} </code></pre> <p>Note that <code>ts</code> is <code>None</code> in the result, cause <code>number</code> was not set when the mapping function executed.</p> <p><strong>edit 2</strong></p> <p>AFAIK the only way to pass a parameter to <code>map</code> is by using <code>scope</code> optional parameter in <code>map_reduce</code>, but then you'll have to remove it from map signature anyway.</p> <p>So by changing your map to:</p> <pre><code>map = Code("function() {" "emit({" "ts : new Date(new Date((this.ts - (this.ts % (60 * number))) * 1000).setSeconds(0))" "}, 1);" "}") </code></pre> <p>and by calling:</p> <pre><code>db.whatever.map_reduce(map, reduce, "collection_name", scope = {"number" : the_value_your_function_needs}) </code></pre> <p>you can get the result you want.</p>
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    1. COThe number param for the map function is so that I'm able to group the collections by closest 5, 10 or X minutes. The parameter works fine if i change the ts-prop to ex, ts : number
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    2. CO@Jarsäter that's curious, cause as far as I can see it returns `None` as the only key in map-reduce result, and it's totally in accord with my answer.
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