[{"title":"This is a title","Post":"this is a post"},{"title":"This is a title 2","Post":"this is a post"},{"title":"This is a title","Post":"this is a post"},{"title":"This is a title 2","Post":"this is a post"}]

db.collection.update({"title":"This is a title 2"},{$set:{"title":"This is a title 3"}},{multi:true})