Mongodb how to get OR of two aggregated queries? - mongodb

Question

I'm using following aggregated query to get results (let say query1):
db.fb.aggregate(
[
{
$addFields : { noOfLikes : { $sum : { $map : { input : "$facebookEvents", as : "f", in : {$cond : [ { $eq : ["$$f.type" , "like"] }, 1, 0 ]} }}}}
},
{
$match : {"noOfLikes" : {$gte : 2}}
}
]
)
and another query to get some other results (let's say query2):
db.fb.aggregate(
[
{ $match : { author : "dave" } },
{ $match : { test : "test1" } }
]
)
Is it possible to get query1 OR query2 using a single aggregate query? In other words, I want to get results that match either query1 or query2 using a single query. Appreciate any help
mongo version: 3.4.4

Answer 1

Within a single aggregate query, you would need to run your pipeline as follows:
db.fb.aggregate([
{
"$addFields": {
"noOfLikes": {
"$sum" : {
"$map": {
"input": "$facebookEvents",
"as": "f",
"in": {
"$cond": [{ "$eq": ["$$f.type" , "like"] }, 1, 0 ]
}
}
}
}
}
},
{
"$match" : {
"$or": [
{ "noOfLikes" : { "$gte" : 2 } },
{ "author": "dave", "test": "test1" }
]
}
}
])
or using $redact as:
db.fb.aggregate([
{
"$redact": {
"$cond": [
{
"$or": [
{ "$gte": [
{
"$sum" : {
"$map": {
"input": "$facebookEvents",
"as": "f",
"in": {
"$cond": [
{ "$eq": ["$$f.type" , "like"] },
1,
0
]
}
}
}
}, 2 ]
},
{
"$and": [
{ "$eq": ["$author", "dave"] },
{ "$eq": ["$test", "test1"] }
]
}
]
},
"$$KEEP",
"$$PRUNE"
]
}
}
])

Answer 2

You can use $facet
db.fb.aggregate(
{
$facet : {
byLikes : [
{ $addFields : { noOfLikes : { $sum : { $map : { input : "$facebookEvents", as : "f", in : {$cond : [ { $eq : ["$$f.type" , "like"] }, 1, 0 ]} }}}} },
{ $match : {"noOfLikes" : {$gte : 2}}}
],
byAuthor : [
{ $match : { author : "dave" } },
{ $match : { test : "test1" } }
]
}
}
)