The v5 patch does not apply anymore, and here is a new rebase. There
are two main changes in v6:
* I choose to use the check I proposed earlier to determine whether a
relation has been unique-ified in costsize.c.
* Now that the only call to relation_has_unique_index_for() that
supplied an exprlist and oprlist has been removed, the loop handling
those lists is effectively dead code. 0002 removes that loop and
simplifies the function accordingly.
Thanks
Richard
