> The idea of the mixed mode is that you want to reduce the odds someone will
> get a massively wrong configuration if they're not paying attention. Is it
> worse to suffer from additional query overhead if you're sloppy with the
> tuning tool, or to discover addition partitions didn't work as you expected?
> That's a tough call; I could invert things, so that it defaults to off in
> mixed mode, as always, and just produces a HINT to turn it on. I don't have
> a really strong opinion there either way.
I think that the strong feelings about default_statistics_target and
constraint_exclusion come from the fact that when they are too low (in
the first case) or off (in the second case), you can get very, very
bad query plans. The penalties in the opposite direction are more
subtle. If they're so subtle that we don't care about incurring them,
then let's change initdb too. If not, then let's not have the tuning
tool generate them by default either.
...Robert