presto-hive/src/main/java/io/prestosql/plugin/hive/HivePageSink.java/HivePageSink/extractColumns
class HivePageSink:    private static Page extractColumns(Page page, int[] columns)
    {
        Block[] blocks = new Block[columns.length];
        for (int i = 0; i < columns.length; i++) {
            int dataColumn = columns[i];
            blocks[i] = page.getBlock(dataColumn);
        }
        return new Page(page.getPositionCount(), blocks);
    }