In response to "Khalid Baheyeldin" <kb@2bits.com>:
Well, I did some benchmarks, and they show that, out of the box at least, MySQL is faster.
Unfortunately, that really doesn't mean anything. I don't know about the configs that ship with Ubuntu, but the PGDG configs produce lousy performance. It's a known factor that the default configs are not tuned for performance and actually perform pretty badly. Based on your "Future considerations" section, if you send me the specs for the hardware this is running, and a copy of the postgresql.conf file, I'll send you a tweaked file to retest with. There is, however a chance that PostgreSQL simply isn't going to run as fast as MySQL. This is, in part, because Drupal is written (primarily) by MySQL people. I'm willing to bet that most of them don't even know when they're taking advantage of things in MySQL that are unusually fast (MySQL, for example is faster at executing simply SELECT queries than anything else out there, whereas PostgreSQL is faster at complex joins ... if Drupal fetches related data from 5 tables in five separate SELECTS instead of 1 big SELECT with a bunch of joins, then it will always be faster on MySQL). In any event, once you've run the tests, I'd like a copy of your PostgreSQL query log, which I can then analyze to see if there's any way to improve speed. Hopefully there will be ways to optimize queries that doesn't hurt MySQL's performance. I have one additional question. You say the following: "MySQL's query cache makes its performance better. This can be demonstrated by restarting MySQL, then visiting the home page of the site and seeing the query time in devel's output. However this is not as marked as what PostgreSQL takes." Could you explain/clarify that statement? -- Bill Moran http://www.potentialtech.com