presto-memory/src/main/java/io/prestosql/plugin/memory/MemoryPagesStore.java/MemoryPagesStore/getColumns
class MemoryPagesStore:    private static Page getColumns(Page page, List<Integer> columnIndexes)
    {
        Block[] outputBlocks = new Block[columnIndexes.size()];

        for (int i = 0; i < columnIndexes.size(); i++) {
            outputBlocks[i] = page.getBlock(columnIndexes.get(i));
        }

        return new Page(page.getPositionCount(), outputBlocks);
    }