Discussion

B-trees and database indexes

jiveturkey: > MySQL, arguably the world's most popular database management system,

whartung: I keep hearing about the downside of B(+)-Trees for DBs, that they have issues for certain scenarios, but I've never seen a simple, detailed list about them, what they are, and the scenarios they perform badly in.

bddicken: Oh hey, I wrote this! Happy to chat more about the article here. Databases are kinda my thing.

amarant: Thanks for writing this! The visualisations really drive a better understanding than pure text does, and it's quite clear that you have a better understanding of what database do under the hood than I do.As such, I have a question for you: contrary to your article, I've always been taught that random primary keys are better than sequential ones. The reason for this, I was told, was to avoid "hotspots". I guess it only really applies once sharding comes into play, and perhaps also only if your primary key is your sharding key, but I think that's a pretty common setup.I'm not really sure how to formulate a concrete question here, I guess I would like to hear your thoughts on any tradeoffs on sequential Vs random keys in sharded setups? Is there a case there random keys are valid, or have I been taught nonsense?