Türker Yıldırım
Twice the throughput and half the memory, for a migration that is mostly deletions — plus the four behaviour changes nobody puts in the upgrade notes.
Adding a field to a mapping is fine. Changing one — a string to a date, an analyzer, a field from analysed to keyword — is not, because…
Shipping used to be a global list of methods each carrying its own availability rules, which meant every method had to know about every country. 2.6 inverted it:…
4.2 seconds on 60,000 rows. Following EXPLAIN from a full table scan to a covering index, and why the composite index that existed was never used.
4.2 to 5.0 is not an upgrade, it is a relocation. Moving an application through it in an order that keeps it booting at every step.