[{"_id":1,"title":"The Pillars of Society","artist":"Grosz","tags":["painting","satire","Expressionism","caricature"]},{"_id":2,"title":"Melancholy III","artist":"Munch","tags":["woodcut","Expressionism"]},{"_id":3,"title":"Dancer","artist":"Miro","tags":["oil","Surrealism","painting"]},{"_id":4,"title":"The Great Wave off Kanagawa","artist":"Hokusai","tags":["woodblock","ukiyo-e"]},{"_id":5,"title":"The Persistence of Memory","artist":"Dali","tags":["Surrealism","painting","oil"]},{"_id":6,"title":"Composition VII","artist":"Kandinsky","tags":["oil","painting","abstract"]},{"_id":7,"title":"The Scream","artist":"Munch","tags":["Expressionism","painting","oil"]},{"_id":8,"title":"Blue Flower","artist":"O'Keefe","tags":["abstract","painting"]}]

db.collection.aggregate([{$facet:{"field1":[{$match:{"artist":"Munch"}}],"field2":[{$match:{"artist":"Grosz"}}]}}])