v.20.1Improvement
Remove ORDER BY Stage from Mutations and Enforce Row Order Check
Remove ORDER BY stage from mutations because we read from a single ordered part in a single thread. Also add check that the order of rows in mutation is ordered in sorting key order and this order is not violated. #9886 (alesapin).Why it matters
To improve mutation efficiency by eliminating unnecessary sorting during mutation processing. This optimization relies on the guarantee that data read during mutations is already ordered. The added check ensures data consistency by verifying that mutation rows preserve sorting key order, thus maintaining correct order semantics and preventing potential errors.How to use it
No explicit user action is required to enable this optimization. The mutationORDER BY stage has been removed internally, and the system now automatically checks that the mutation rows are ordered according to the sorting key.