Re: WIP: patch to create explicit support for semi and anti joins

>>> Tom Lane <tgl@sss.pgh.pa.us> wrote: 
> Introduce JOIN_SEMI and JOIN_ANTI join types, the former replacing
> JOIN_IN.  Unify the InClauseInfo and OuterJoinInfo infrastructure
into
> "SpecialJoinInfo".  Convert IN, EXISTS, and NOT EXISTS clauses at
top
> level of WHERE into semi and anti joins respectively.
It just struck me that this may cause additional joins to count
against the join_collapse_limit.  If so, that could cause some
borderline queries to optimize poorly if the limit isn't raised.  Is
that a reasonable concern?  Possibly something to document in the
release notes?
-Kevin