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POMap/Reduce to get group() Result
 

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  1. POMap/Reduce to get group() Result
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    <p>I'm trying to aggregate a bunch of user profile data in our app. Each user has an embedded profile document with a gender, and ethnicity attribute.</p> <pre><code>{ 'email': 'foo@email.com', 'profile': { 'gender': 'male', 'ethnicity': 'Hispanic' } } </code></pre> <p>If I use a group function like so:</p> <pre><code>db.respondents.group({ key: {}, initial: {'gender': {'male':0,'female':0}, 'ethnicity': {}, 'count': 0}, reduce: function (user, totals) { var profile = user.profile; totals.gender[profile.gender]++; totals.ethnicity[profile.ethnicity] = (totals.ethnicity[profile.ethnicity] || 0); totals.ethnicity[profile.ethnicity]++ totals.count++; } }); </code></pre> <p>I get the result in the form I want:</p> <pre><code>{ "gender" : { "male" : ###, "female" : ### }, "ethnicity" : { "Caucasian/White" : ###, "Hispanic" : ###, ... }, "count" : ### } </code></pre> <p>I'm having trouble getting this to work as a map/reduce command, using a different reduce function of course. I'm not sure how to get the totals to add up. They are always incorrect. I'm aware that my output from reduce has to be in the same format as the input from map, but I feel like I'm missing something in the way that reduce works...</p> <p>In response to @Jenna, the input looks like:</p> <pre><code>{ 'email': 'foo@email.com', 'profile': { 'gender': 'male', 'ethnicity': 'Hispanic' } } </code></pre> <p>and the functions are:</p> <pre><code>function map(){ emit('demographics', this.profile) } function reduce (key, values) { var reduced = {'gender': {'male':0,'female':0}, 'ethnicity': {}, 'count': 0}; values.forEach(function(value) { reduced.gender[value.gender]++; reduced['ethnicity'][value.ethnicity] = (reduced['ethnicity'][value.ethnicity] || 0); reduced['ethnicity'][value.ethnicity]++; reduced.count++; }); return reduced; } </code></pre> <p>and the output is: </p> <pre><code>{ "_id": "demographics", "value": { "gender": { "male": 76.0, "female": 64.0 }, "ethnicity": { "Caucasian/White": 109.0, "Other": 5.0, "Asian": 10.0, "African-American": 8.0, "Hispanic": 7.0, "Native American": 1.0 }, "count": 141.0 } } </code></pre> <p>The output is way incorrect since there are over 100k records in the database.</p>
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    1. USRipTheJacker
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    1. COCan you post your map and reduce functions as well as an example of your input and output?
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      1. USJenna
    2. CO@Jenna - I added the additional info to the post. Thanks for taking a look!
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    3. CONo problemo :) Can you also post the stats that are printed when you run your map reduce command? For example, when I run map reduce in the shell it outputs the following fields: result, timeMillis, counts:{input: x, emit: y, reduce: z, output: x}
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