Re: NOT IN subquery optimization

You should do small rebase (conflict with 911e7020770) and pgindent of 
the patch to repair problems with long lines and backspaces.

I am reviewing your patch in small steps. Questions:
1. In the find_innerjoined_rels() routine you stop descending on 
JOIN_FULL node type. I think it is wrong because if var has NOT NULL 
constraint, full join can't change it to NULL.
2. The convert_NOT_IN_to_join() routine is ok, but its name is 
misleading. May be you can use something like make_NOT_IN_to_join_quals()?
3. pull_up_sublinks_qual_recurse(). Comment:
"Return pullout predicate (x is NOT NULL)..."
may be change to
"Return pullout predicate (x is NOT NULL or NOT EXISTS...)"?
4. is_node_nonnullable():
I think one more case of non-nullable var may be foreign key constraint.

-- 
Andrey Lepikhov
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