Created
November 27, 2013 19:49
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MongoDB training aggregation exercises
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| db.twitter.aggregate( | |
| { $group : { | |
| "_id" : "$user.screen_name", | |
| "tweets" : { $sum : 1 } | |
| } | |
| }, | |
| { $sort : { "tweets" : -1 } }, | |
| { $limit : 5 } | |
| ) | |
| db.twitter.aggregate( | |
| { $unwind : "$entities.user_mentions" }, | |
| { $group : { "_id" : "$user.screen_name", | |
| "does_mention" : { $sum : 1 } } | |
| }, | |
| { $sort : { "does_mention" : -1 } }, | |
| { $limit : 5 } | |
| ) | |
| db.twitter.aggregate( | |
| { $unwind : "$entities.user_mentions" }, | |
| { $group : { | |
| "_id" : "$user.screen_name", | |
| "mentioned" : { $addToSet : "$entities.user_mentions.screen_name" } | |
| } | |
| }, | |
| { $unwind : "$mentioned" }, | |
| { $group : { | |
| "_id" : "$_id", | |
| "mention_count" : { $sum : 1 } | |
| } | |
| }, | |
| { $sort : { "mention_count" : -1 } }, | |
| { $limit : 5 } | |
| ) | |
| // Highest ratio | |
| db.twitter.aggregate( | |
| { $match : { | |
| "user.friends_count" : { $gt : 0 } , | |
| "user.followers_count" : { $gt : 0 } | |
| } | |
| }, | |
| { $project : { | |
| "user.screen_name" : 1, | |
| "ratio" : { $divide : [ "$user.followers_count", "$user.friends_count" ] }, | |
| "user.friends_count" : 1, | |
| "user.followers_count" : 1 | |
| } | |
| }, | |
| { $sort : { "ratio" : -1 } }, | |
| { $limit : 1 } | |
| ) | |
| // Lowest ratio | |
| db.twitter.aggregate( | |
| { $match : { | |
| "user.friends_count" : { $gt : 0 } , | |
| "user.followers_count" : { $gt : 0 } | |
| } | |
| }, | |
| { $project : { | |
| "user.screen_name" : 1, | |
| "ratio" : { $divide : [ "$user.followers_count", "$user.friends_count" ] }, | |
| "user.friends_count" : 1, | |
| "user.followers_count" : 1 | |
| } | |
| }, | |
| { $sort : { "ratio" : 1 } }, | |
| { $limit : 1 } | |
| ) | |
| // Average ratio | |
| db.twitter.aggregate( | |
| { $match : { | |
| "user.friends_count" : { $gt : 0 } , | |
| "user.followers_count" : { $gt : 0 } | |
| } | |
| }, | |
| { $project : { | |
| "user.screen_name" : 1, | |
| "ratio" : { $divide : [ "$user.followers_count", "$user.friends_count" ] }, | |
| "user.friends_count" : 1, | |
| "user.followers_count" : 1 | |
| } | |
| }, | |
| { $group : { | |
| _id : "whatever", | |
| "sum" : { $sum : "$ratio" }, | |
| "count" : { $sum : 1 }, | |
| } | |
| }, | |
| { $project : { | |
| _id : 1, | |
| avg : { $divide : [ "$sum", "$count" ] } | |
| } | |
| } | |
| ) | |
| // Closest to average | |
| db.twitter.aggregate( | |
| { $match : { | |
| "user.friends_count" : { $gt : 0 } , | |
| "user.followers_count" : { $gt : 0 } | |
| } | |
| }, | |
| { $project : { | |
| "user.screen_name" : 1, | |
| "ratio" : { $divide : [ "$user.followers_count", "$user.friends_count" ] }, | |
| "user.friends_count" : 1, | |
| "user.followers_count" : 1 | |
| } | |
| }, | |
| { $project : { | |
| "user.screen_name" : 1, | |
| "difference" : { $subtract : [ "$ratio", 8.044204413696734 ] } | |
| } | |
| }, | |
| { $project : { | |
| "user.screen_name" : 1, | |
| "abs_difference" : { | |
| $cond : [ | |
| { $lt : [ "$difference", 0 ] }, | |
| { $multiply : [ "$difference", -1 ] }, | |
| "$difference" | |
| ] | |
| } | |
| } | |
| }, | |
| { $sort : { "abs_difference" : 1 } }, | |
| { $limit : 1 } | |
| ) | |
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