db={"temporari":[{entityId:"c1",entity:"commodities"}],"commodities":[{_id:"c1"}],"posts":[{_id:"p1"}]}

db.temporari.aggregate([{"$lookup":{"from":"commodities","let":{eid:"$entityId",e:"$entity"},pipeline:[{"$match":{$expr:{$and:[{$eq:["$$eid","$_id"]},{$eq:["$$e","commodities"]}]}}}],"as":"commoditiesLookup"}},{"$lookup":{"from":"posts","let":{eid:"$entityId",e:"$entity"},pipeline:[{"$match":{$expr:{$and:[{$eq:["$$eid","$_id"]},{$eq:["$$e","posts"]}]}}}],"as":"postsLookup"}},{"$addFields":{"orders_info":{"$setUnion":["$commoditiesLookup","$postsLookup"]}}}])