[{"_id":"1","firstName":"John","last_name":"Doe","message_id":"12345","messages":[{"time":"Thu Aug 05 2021 19:31:15 GMT-0700 (Pacific Daylight Time)","text":"hey there"},{"time":"Thu Aug 05 2021 19:34:15 GMT-0700 (Pacific Daylight Time)","text":"what's up"},{"time":"Thu Aug 05 2021 19:37:15 GMT-0700 (Pacific Daylight Time)","text":"hey"},],"__v":0},{"_id":"2","firstName":"Jane","last_name":"Doe","message_id":"12345","messages":[{"time":"Thu Aug 05 2021 19:32:15 GMT-0700 (Pacific Daylight Time)","text":"hey buddy"},{"time":"Thu Aug 05 2021 19:35:15 GMT-0700 (Pacific Daylight Time)","text":"not much, what about you?"},{"time":"Thu Aug 05 2021 19:38:15 GMT-0700 (Pacific Daylight Time)","text":"hello!"},],"__v":0},]

db.collection.aggregate([{$match:{"messages.text":{"$regex":".*hey.*"}}},{$unwind:"$messages"},{$match:{"messages.text":{"$regex":".*hey.*"}}},{$group:{_id:"$_id",messages:{"$addToSet":{time:"$messages.time",text:"$messages.text"}},"firstName":{$first:"$firstName"},"last_name":{$first:"$last_name"},"message_id":{$first:"$message_id"},}},{$sort:{_id:1}}])