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Type:
Bug
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Resolution: Fixed
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Priority:
Major - P3
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Affects Version/s: None
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Labels:
Based on server ticket SERVER-22881, the text in $lookup documentation saying that an $unwind is necessary is no longer accurate.
$unwind may still be used for prettier formatting, but the same can be accomplished on the other side of the $lookup with $project and some other expressions.
Using the same sample documents in the document example, see the following pipeline and output.
db.orders.aggregate([
{
$lookup:
{
from: "inventory",
localField: "specs",
foreignField: "size",
as: "inventory_docs"
}
},
{
$match: { "inventory_docs": { $ne: [] } }
}
])
{
"_id" : 1,
"item" : "MON1003",
"price" : 350,
"quantity" : 2,
"specs" : [
"27 inch",
"Retina display",
"1920x1080"
],
"type" : "Monitor",
"inventory_docs" : [
{
"_id" : 1,
"sku" : "MON1003",
"type" : "Monitor",
"instock" : 120,
"size" : "27 inch",
"resolution" : "1920x1080"
}
]
}
- related to
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DOCS-10894 $lookup docs should mention the $lookup+$unwind optimization
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- Closed
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