presto-mongodb/src/main/java/io/prestosql/plugin/mongodb/MongoPageSource.java/MongoPageSource/MongoPageSource
class MongoPageSource:    public MongoPageSource(
            MongoSession mongoSession,
            MongoTableHandle tableHandle,
            List<MongoColumnHandle> columns)
    {
        this.columnNames = columns.stream().map(MongoColumnHandle::getName).collect(toList());
        this.columnTypes = columns.stream().map(MongoColumnHandle::getType).collect(toList());
        this.cursor = mongoSession.execute(tableHandle, columns);
        currentDoc = null;

        pageBuilder = new PageBuilder(columnTypes);
    }