Remove AssertArg and AssertState
These don't offer anything over plain Assert, and their usage had
already been declared obsolescent.
Author: Nathan Bossart
Reviewed-by: Michael Paquier
Discussion:
https://www.postgresql.org/message-id/20221009210148.GA900071@nathanxps13
Branch
--
master
Use Limit instead of Unique to implement DISTINCT, when possible
When all of the query's DISTINCT pathkeys have been marked as redundant
due to EquivalenceClasses existing which contain constants, we can just
implement the DISTINCT operation on a query by just limiting the number of
returned rows
