presto-main/src/main/java/io/prestosql/connector/informationschema/InformationSchemaPageSource.java/InformationSchemaPageSource/getNextPage
class InformationSchemaPageSource:    @Override
    public Page getNextPage()
    {
        if (isFinished()) {
            return null;
        }

        if (pages.isEmpty()) {
            buildPages();
        }

        Page page = pages.poll();

        if (page == null) {
            return null;
        }

        memoryUsageBytes -= page.getRetainedSizeInBytes();
        Page outputPage = projection.apply(page);
        completedBytes += outputPage.getSizeInBytes();
        return outputPage;
    }