Haal de testgegevens op van dit MongoPlaygroud-link.
OPMERKING :U kunt alle $sort . overslaan stadia in de bovenstaande link omwille van de prestaties.
Vraag om het aantal bladeren te krijgen:
db.Forests.aggregate([
{ $unwind: "$trees" },
{ $unwind: "$trees.branches" },
{
$lookup: {
from: "Leaves",
localField: "trees.branches.branch_id",
foreignField: "branch_id",
as: "trees.branches.leaves"
}
},
{
$addFields: {
"trees.branches.leaf_count": { $size: "$trees.branches.leaves" }
}
},
{
$project: { "trees.branches.leaves": 0 }
},
{
$group: {
_id: {
forest_id: "$forest_id",
tree_id: "$trees.tree_id"
},
leaf_count: { $sum: "$trees.branches.leaf_count" },
branches: { $push: "$trees.branches" }
}
},
{
$group: {
_id: "$_id.forest_id",
leaf_count: { $sum: "$leaf_count" },
trees: {
$push: {
leaf_count: { $sum: "$leaf_count" },
tree_id: "$_id.tree_id",
branches: "$branches"
}
}
}
},
{
$group: {
_id: null,
leaf_count: { $sum: "$leaf_count" },
forests: {
$push: {
leaf_count: { $sum: "$leaf_count" },
forest_id: "$_id",
trees: "$trees"
}
}
}
},
{
$project: { _id: 0 }
}
])
Uitgang:
{
"leaf_count" : 4,
"forests" : [
{
"leaf_count" : 3,
"forest_id" : "forestA",
"trees" : [
{
"leaf_count" : 2,
"tree_id" : "treeA",
"branches" : [
{
"branch_id" : "branchA",
"leaf_count" : 1
},
{
"branch_id" : "branchA1",
"leaf_count" : 1
},
{
"branch_id" : "branchA2",
"leaf_count" : 0
}
]
},
{
"leaf_count" : 1,
"tree_id" : "treeB",
"branches" : [
{
"branch_id" : "branchB",
"leaf_count" : 1
}
]
}
]
},
{
"leaf_count" : 1,
"forest_id" : "forestB",
"trees" : [
{
"leaf_count" : 1,
"tree_id" : "treeC",
"branches" : [
{
"branch_id" : "branchC",
"leaf_count" : 1
}
]
},
{
"leaf_count" : 0,
"tree_id" : "treeD",
"branches" : [
{
"branch_id" : "branchD",
"leaf_count" : 0
}
]
}
]
},
{
"leaf_count" : 0,
"forest_id" : "forestC",
"trees" : [
{
"leaf_count" : 0,
"tree_id" : "treeE",
"branches" : [
{
"branch_id" : "branchE",
"leaf_count" : 0
}
]
}
]
}
]
}