> Interference with upgrades: today's helpful hints become anti-performance after an upgrade.
> Encouraging bad DBA habits slap a hint on instead of figuring out the real issue.
Does not scale with data size: the hint that's right when a table is small is likely to be wrong when it gets larger.
> Failure to actually improve query performance: most of the time, the optimizer is actually right.
> Interfering with improving the query planner: people who use hints seldom report the query problem to the project.
> Interference with upgrades: today's helpful hints become anti-performance after an upgrade.
> Encouraging bad DBA habits slap a hint on instead of figuring out the real issue. Does not scale with data size: the hint that's right when a table is small is likely to be wrong when it gets larger.
> Failure to actually improve query performance: most of the time, the optimizer is actually right.
> Interfering with improving the query planner: people who use hints seldom report the query problem to the project.
https://wiki.postgresql.org/wiki/OptimizerHintsDiscussion