Or "joins are too slow". Well, yes, they can be. But some database systems have smarter plan builders than others.
Take, for example, this gem:
> Joining and ordering by rows from multiple tables often forces MySQL to dump the whole join to a temporary table, then sort it -- awful, especially if you then use LIMIT BY to paginate the results.
This describes just about every standard page-with-comments schema ever devised.
It struck me with particular force because perhaps I've been unfairly blaming Wordpress for the failings of MySQL, vis-a-vis the atrocious performance of the Recent Comments Widget.
I see horrible join performance on tables with about half a million rows, which is chicken feed. The query cache "solves" my problem, but it's amazing that it should be necessary for very trivial joins between 2 or 3 tables.
Take, for example, this gem:
> Joining and ordering by rows from multiple tables often forces MySQL to dump the whole join to a temporary table, then sort it -- awful, especially if you then use LIMIT BY to paginate the results.
This describes just about every standard page-with-comments schema ever devised.
It struck me with particular force because perhaps I've been unfairly blaming Wordpress for the failings of MySQL, vis-a-vis the atrocious performance of the Recent Comments Widget.
I see horrible join performance on tables with about half a million rows, which is chicken feed. The query cache "solves" my problem, but it's amazing that it should be necessary for very trivial joins between 2 or 3 tables.