[zasdffaa]

> We've never had a rule change from being beneficial to detrimental

Whatever you're doing is really confusing me (see my prev post). A multi-thousand line piece of the SQL I wrote was tested on mssql 2019 and there was a blatant perf. fuckup from it's previous home on mssql 2016 (or was it 2014). Poss. down to the new cardinality estimator, I dunno.

> For example, when we trim joins from inner queries, we first trim their selections (depending on what is actually used in the outer queries).

If you looked at the query plans you will see this happens automatically. And very reliably because it is easy (indeed, quite straightforward) to do automatically.

Also... 'we just read release notes' - these optimisations are not documented (except maybe in one place which they carefully undocumented after the 1st release) because these are trade secrets. The optimiser is one of the most important and carefully guarded parts of mssql - it's not in the notes and never will be.

No offence but... seriously, wat???