presto-mongodb/src/main/java/io/prestosql/plugin/mongodb/MongoSession.java/MongoSession/execute
class MongoSession:    public MongoCursor<Document> execute(MongoTableHandle tableHandle, List<MongoColumnHandle> columns)
    {
        Document output = new Document();
        for (MongoColumnHandle column : columns) {
            output.append(column.getName(), 1);
        }
        MongoCollection<Document> collection = getCollection(tableHandle.getSchemaTableName());
        FindIterable<Document> iterable = collection.find(buildQuery(tableHandle.getConstraint())).projection(output);

        if (cursorBatchSize != 0) {
            iterable.batchSize(cursorBatchSize);
        }

        return iterable.iterator();
    }