A CMS keeps an array of tags right on the article row — e.g. {'sql', 'postgres', 'index'}. Analytics wants a «top tags» view: how many articles are tagged with each tag. To compute this, the array must be «unfolded» into rows — every array element becomes a separate row, then it's a regular grouping. The table articles(id, title, tags TEXT[]) holds three articles. For every tag present in the arrays, count the number of articles that contain it. Sort by count descending, ties broken by tag alphabetically.