mongo count elements in array

Lucky Lobster answered on December 9, 2020 Popularity 9/10 Helpfulness 4/10

answer mongo count elements in array

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mongo count elements in array

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{ $size: <expression> }

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Source: docs.mongodb.com

Tags: count elements typescript

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Contributed on Dec 09 2020

Lucky Lobster

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mongo count elements in array

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> db.mycollection.insert({'foo':[1,2,3,4]})
> db.mycollection.insert({'foo':[5,6,7]})

> db.mycollection.aggregate([{$project: { count: { $size:"$foo" }}}])
{ "_id" : ObjectId("5314b5c360477752b449eedf"), "count" : 4 }
{ "_id" : ObjectId("5314b5c860477752b449eee0"), "count" : 3 }

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Source: stackoverflow.com

Tags: count coun

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Contributed on Dec 09 2020

Lucky Lobster

0 Answers Avg Quality 2/10

Mongodb count based on array of ids

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db.collection.aggregate([
    { $unwind: "$connects" },

    // count all occurrences
    { "$group": { "_id": {skill: "$skill", parser_id: "$connects.parser_id"}, "count": { "$sum": 1 } }},

    // sum all occurrences and count distinct
    { "$group": { "_id": "$_id.skill", "quantity": { "$sum": 1 } }},

    // (optional) rename the '_id' attribute to 'skill'
    { $project: { 'skill': '$_id', 'quantity': 1, _id: 0 } }
])

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Source: stackoverflow.com

Tags: ids typescript ty

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Contributed on Apr 19 2021

Witty Wildebeest

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mongo count elements in array

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mongo count elements in array

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