Understanding database indexes in PostgreSQL
That was more detailed than I expected, a lot of posts on this topic tend to be more superficial. I suspect the BRIN index might need a bit of a stronger disclaimer, as far as I understand you really want to use that only for ordered data, and in those cases it is exceptionally good at its job. But it is a lot worse if that condition is not met. The post mentions this a bit, but with very soft language.I disagree a bit with "Don’t index columns if the table has little data", mostly because it doesn't matter in those cases. If the table is tiny the index is also very cheap (unless it's something really weird like a tiny table that is written at a very high frequency). And "little data" is just not specific enough for people to make decisions unless they already have a very good intuition on when the query planner would use such an index.A rather important part that isn't mentioned about multi-column indexes is which kinds of query can use them. That is probably not obvious if you never read about them in detail, but it's really important to know when defining them.