[jclulow]

One challenge with that is that the query plan often depends on the current table composition statistics. If a value is relatively common (or uncommon), or the size of the table has grown or shrunk, you may end up with a materially different (and conceivably substantially worse) plan.

[tomnipotent]

I can't tell you how many times over 20 years I've heard a DBA tell me "the statistics weren't updated" after an incident.

[ovi256]

I've written cron jobs to update mysql statistics to prevent it from choosing bad query plans. It's as terrible as it sounds.

[pas]

How come it's not automatic and built-in? Why is a script terrible? (Does it have to enumerate all tables and piecewise run the stat update?)

[ovi256]

Yes, the stats update is per table. We only updated it for a few tables we really cared about.

[silon42]

This is my reason for preferring NOSQL where possible.