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Type:
New Feature
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Resolution: Unresolved
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Priority:
Major - P3
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None
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Affects Version/s: None
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Component/s: Aggregation Framework
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None
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Query Optimization
Although it's possible to aggregate data and use a weighted average (https://support.microsoft.com/en-ca/help/214049/how-to-calculate-weighted-averages-in-excel), it is very cumbersome requiring a nested set of group and projection aggregates. See https://stackoverflow.com/questions/46739027/using-weighted-average-with-mongodb-and-group.
I would like to see a weighted average accumulator function along with $avg. e.g.
db.sales.aggregate(
[
{
$group : {
_id : { month: { $month: "$date" }, day: { $dayOfMonth: "$date" }, year: { $year: "$date" } },
totalPrice: { $sum: { $multiply: [ "$price", "$quantity" ] } },
averageQuantity: { $weighted_avg: { $value : "$quantity", $weight: "$weight" },
count: { $sum: 1 }
}
}
]
)