3 ms·Or if it’s MySQL, the PK is implicitly copied into every secondary index. Adds up quickly.by sgarland 2y agoOr if it’s MySQL, the PK is implicitly copied into every secondary index. Adds up quickly.pyuser583 2y agoWow did not know that. MySQL has tons of hidden behavior.sgarland 2y agoSo does Postgres to an extent, but in general, MySQL has more hidden edge cases, and Postgres has more hidden maintenance requirements.