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by simmschi
2 days ago
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FINALLY! I never understood the issues PG had with hints. Running a non-trivial DB with a non-trivial schema and scale is, well, non-trivial at all. At some point the DB stops being a black box and starts being a tool that you have to know inside and out to avoid performance issues. >The optimizer is usually smarter than you think. Except for when it isn't, and moves heavy calculation inside a nested loop inside a nested loop to avoid an index scan. Nothing is perfect. |
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> Except for when it isn't, and moves heavy calculation inside a nested loop inside a nested loop to avoid an index scan. Nothing is perfect.
Yeah that's also been my experience. It's true that Postgres is usually smarter than I think, when I try to figure out why it's not using a better query plan I eventually find out that it wouldn't be better at all. But from time to time, it genuinely is taking a bad decision and having no power over that at all is a problem