$reduce and $setUnion for nested arrays in MongoDB
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I am looking to merge nested arrays using $reduce and $setUnion in MongoDB. Following is the sample input -
levels: [
[[80,100,120]],[[100,150]],[[200,80,100]],[[80,100]]
]
The output what I am intended to get (i.e. merge nested arrays with unique values) -
levels: [80,100,120,150,100]
I am able to get the above output using two ways -
1) Using two $project stages in pipeline -
aggregate([
$project: { levels : { $reduce: {
input: "$levels", initialValue: , in:{$setUnion:["$$value","$$this"]}}}},
$project: { levels : { $reduce: {
input: "$levels", initialValue: , in:{$setUnion:["$$value","$$this"]}}}}
])
2) First $unwind and then $project
aggregate([
$unwind: { '$levels'}},
$project: { levels : { $reduce: {
input: "$levels", initialValue: , in:{$setUnion:["$$value","$$this"]}}}}
])
Can there be any improved way of first option where I don't need to use the same $project twice? I am trying to avoid unwind.
mongodb mongodb-query aggregation-framework
asked Nov 29 '18 at 5:37
AkashAkash
19519
add a comment |
I am looking to merge nested arrays using $reduce and $setUnion in MongoDB. Following is the sample input -
levels: [
[[80,100,120]],[[100,150]],[[200,80,100]],[[80,100]]
]
The output what I am intended to get (i.e. merge nested arrays with unique values) -
levels: [80,100,120,150,100]
I am able to get the above output using two ways -
1) Using two $project stages in pipeline -
aggregate([
$project: { levels : { $reduce: {
input: "$levels", initialValue: , in:{$setUnion:["$$value","$$this"]}}}},
$project: { levels : { $reduce: {
input: "$levels", initialValue: , in:{$setUnion:["$$value","$$this"]}}}}
])
2) First $unwind and then $project
aggregate([
$unwind: { '$levels'}},
$project: { levels : { $reduce: {
input: "$levels", initialValue: , in:{$setUnion:["$$value","$$this"]}}}}
])
Can there be any improved way of first option where I don't need to use the same $project twice? I am trying to avoid unwind.
mongodb mongodb-query aggregation-framework
asked Nov 29 '18 at 5:37
AkashAkash
19519
add a comment |
I am looking to merge nested arrays using $reduce and $setUnion in MongoDB. Following is the sample input -
levels: [
[[80,100,120]],[[100,150]],[[200,80,100]],[[80,100]]
]
The output what I am intended to get (i.e. merge nested arrays with unique values) -
levels: [80,100,120,150,100]
I am able to get the above output using two ways -
1) Using two $project stages in pipeline -
aggregate([
$project: { levels : { $reduce: {
input: "$levels", initialValue: , in:{$setUnion:["$$value","$$this"]}}}},
$project: { levels : { $reduce: {
input: "$levels", initialValue: , in:{$setUnion:["$$value","$$this"]}}}}
])
2) First $unwind and then $project
aggregate([
$unwind: { '$levels'}},
$project: { levels : { $reduce: {
input: "$levels", initialValue: , in:{$setUnion:["$$value","$$this"]}}}}
])
Can there be any improved way of first option where I don't need to use the same $project twice? I am trying to avoid unwind.
mongodb mongodb-query aggregation-framework
asked Nov 29 '18 at 5:37
AkashAkash
19519
I am looking to merge nested arrays using $reduce and $setUnion in MongoDB. Following is the sample input -
levels: [
[[80,100,120]],[[100,150]],[[200,80,100]],[[80,100]]
]
The output what I am intended to get (i.e. merge nested arrays with unique values) -
levels: [80,100,120,150,100]
I am able to get the above output using two ways -
1) Using two $project stages in pipeline -
aggregate([
$project: { levels : { $reduce: {
input: "$levels", initialValue: , in:{$setUnion:["$$value","$$this"]}}}},
$project: { levels : { $reduce: {
input: "$levels", initialValue: , in:{$setUnion:["$$value","$$this"]}}}}
])
2) First $unwind and then $project
aggregate([
$unwind: { '$levels'}},
$project: { levels : { $reduce: {
input: "$levels", initialValue: , in:{$setUnion:["$$value","$$this"]}}}}
])
Can there be any improved way of first option where I don't need to use the same $project twice? I am trying to avoid unwind.
mongodb mongodb-query aggregation-framework
mongodb mongodb-query aggregation-framework
asked Nov 29 '18 at 5:37
AkashAkash
19519
asked Nov 29 '18 at 5:37
AkashAkash
19519
asked Nov 29 '18 at 5:37
AkashAkash
19519
asked Nov 29 '18 at 5:37
AkashAkash
19519
asked Nov 29 '18 at 5:37
AkashAkash
19519
19519
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
You can use below aggregation with single $project stage
db.collection.aggregate([
{ "$project": {
"levels": {
"$reduce": {
"input": {
"$reduce": {
"input": "$levels",
"initialValue": ,
"in": { "$setUnion": ["$$this", "$$value"] }
}
},
"initialValue": ,
"in": { "$setUnion": ["$$this", "$$value"] }
}
}
}}
])
answered Nov 29 '18 at 5:43
Anthony WinzletAnthony Winzlet
18.3k42346
1
Thank you @Anthony. It is working as expected!
– Akash
Nov 29 '18 at 6:11
add a comment |
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
You can use below aggregation with single $project stage
db.collection.aggregate([
{ "$project": {
"levels": {
"$reduce": {
"input": {
"$reduce": {
"input": "$levels",
"initialValue": ,
"in": { "$setUnion": ["$$this", "$$value"] }
}
},
"initialValue": ,
"in": { "$setUnion": ["$$this", "$$value"] }
}
}
}}
])
answered Nov 29 '18 at 5:43
Anthony WinzletAnthony Winzlet
18.3k42346
1
Thank you @Anthony. It is working as expected!
– Akash
Nov 29 '18 at 6:11
add a comment |
You can use below aggregation with single $project stage
db.collection.aggregate([
{ "$project": {
"levels": {
"$reduce": {
"input": {
"$reduce": {
"input": "$levels",
"initialValue": ,
"in": { "$setUnion": ["$$this", "$$value"] }
}
},
"initialValue": ,
"in": { "$setUnion": ["$$this", "$$value"] }
}
}
}}
])
answered Nov 29 '18 at 5:43
Anthony WinzletAnthony Winzlet
18.3k42346
1
Thank you @Anthony. It is working as expected!
– Akash
Nov 29 '18 at 6:11
add a comment |
You can use below aggregation with single $project stage
db.collection.aggregate([
{ "$project": {
"levels": {
"$reduce": {
"input": {
"$reduce": {
"input": "$levels",
"initialValue": ,
"in": { "$setUnion": ["$$this", "$$value"] }
}
},
"initialValue": ,
"in": { "$setUnion": ["$$this", "$$value"] }
}
}
}}
])
answered Nov 29 '18 at 5:43
Anthony WinzletAnthony Winzlet
18.3k42346
You can use below aggregation with single $project stage
db.collection.aggregate([
{ "$project": {
"levels": {
"$reduce": {
"input": {
"$reduce": {
"input": "$levels",
"initialValue": ,
"in": { "$setUnion": ["$$this", "$$value"] }
}
},
"initialValue": ,
"in": { "$setUnion": ["$$this", "$$value"] }
}
}
}}
])
answered Nov 29 '18 at 5:43
Anthony WinzletAnthony Winzlet
18.3k42346
edited Nov 29 '18 at 5:49
answered Nov 29 '18 at 5:43
Anthony WinzletAnthony Winzlet
18.3k42346
answered Nov 29 '18 at 5:43
Anthony WinzletAnthony Winzlet
18.3k42346
answered Nov 29 '18 at 5:43
Anthony WinzletAnthony Winzlet
18.3k42346
18.3k42346
1
Thank you @Anthony. It is working as expected!
– Akash
Nov 29 '18 at 6:11
add a comment |
1
Thank you @Anthony. It is working as expected!
– Akash
Nov 29 '18 at 6:11
1
1
Thank you @Anthony. It is working as expected!
– Akash
Nov 29 '18 at 6:11
Thank you @Anthony. It is working as expected!
– Akash
Nov 29 '18 at 6:11
add a comment |
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