[sjwright]

> All cost based optimisers rely on statistics being correct. And inevitably there will be a case where they aren't.

Every single time the SQL Server query optimiser did something obviously wrong, rebuilding statistics fixed it. The problem I had with SQL Server wasn't its reliance of statistics—it's not like they could work any other way—it's that it failed to maintain its statistics correctly. Any time that statistics stop being correct is a bug. It should be able to maintain them itself and trigger rebuilds whenever there's any doubt about them.