This looks like an awesome addition.
I have one technical questions...
Is it possible to actually transform the row_number case into a LIMIT
clause or make the planner support for this case equivalent to it (in
which case we can replace the LIMIT clause planning to transform into
a window function)?
The reason I ask is because the Limit plan node is actually quite a
bit more optimized than the general window function plan node. It
calculates cost estimates based on the limit and can support Top-N
sort nodes.
But the bigger question is whether this patch is ready for a committer
to look at? Were you able to resolve Andy Fan's bug report? Did you
resolve the two questions in the original email?
