How do you turn join into a boolean field with the aggregation feature?

• mongoplayground

  6 173 5.3 Go

  a simple sandbox to test and share MongoDB queries

db.testA.aggregate([ { $lookup: { from: "testB", localField: "_id", foreignField: "aId", as: "join" } }, { $addFields: { isFound: { "$function": { // you can remove the enclose quotation in function // this is a bug with mongoplayground // https://github.com/feliixx/mongoplayground/issues/22 "body": "function(a) {return a.length > 0}", args: [ "$join" ], lang: "js" } } } }, { "$project": { isFound: 1 } } ])

• InfluxDB

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