Re: Avoid extra Sort nodes between WindowAggs when sorting can be reused

>>>>> "Tom" == Tom Lane <tgl@sss.pgh.pa.us> writes:

 Tom> * I'm almost thinking that changing to list_union is a bad idea,

A fair point. Though it looks like list_union is used in only about 3
distinct places, and two of those are list_union(NIL, blah) to simply
remove dups from a single list. The third place is the cartesian-product
expansion of grouping sets, which uses list_union_int to remove
duplicates - changing the order there will give slightly user-surprising
but not actually incorrect results.

Presumably list_concat_unique should be considered to guarantee that it
preserves the relative order of the two lists and of the non-duplicate
items in the second list?

-- 
Andrew (irc:RhodiumToad)