After much discussion last year, I'm entirely in support of Julian's abstract goals. However, I'm concerned about the real world impact.
On Tue, Jul 21, 2015 at 12:09 PM, Julian Hyde <[email protected]> wrote: > Yes, I do think these "little" relational expressions can have a very > significant impact. They may block optimizations, they increase size > of the search space (which makes the rule queue longer, and generates > more GC pressure). > > To be clear: it's perfectly fine if client programs (e.g the > SqlToRelConverter) create these expressions. But the planner rules > have to be ruthless in stripping them away. And the engine has to do a > better job of ignoring them after they have been shown to be trivial. > > On Tue, Jul 21, 2015 at 11:55 AM, Vladimir Sitnikov > <[email protected]> wrote: > > I'm not sure if "field names for very top project" play any difference. > > > > As far as I understand, the intention was to keep execution plan > readable. > > > > Julian, can you please highlight why are you thinking of merging > > "project that merely renames"? > > > > Does it block another optimization? > > Does it expand search space much? > > Vladimir >
