MDEV-6480: Remove conditions for which range optimizer returned SEL_ARG::IMPOSSIBLE

Let range optimizer remove parts of OR-clauses for which range analysis
produced SEL_TREE(IMPOSSIBLE).
There is no need to remove parts of AND-clauses: either they are inside
of OR (and the whole AND-clause will be removed), or the AND-clause is
at the top level, in which case the whole WHERE (or ON) is always FALSE
and this is a degenerate case which receives special treatment.

The removal process takes care not to produce 1-way ORs (in that case
we substitute the OR for its remaining member).

1 files changed, 2 insertions, 2 deletions

diff --git a/mysql-test/r/join_outer.result b/mysql-test/r/join_outer.result
index c4770182598..36c2f1898f8 100644
--- a/mysql-test/r/join_outer.result
+++ b/mysql-test/r/join_outer.result
@@ -2090,10 +2090,10 @@ SELECT t1.b, t2.c, t2.d FROM t2 LEFT JOIN t1 ON t2.c = t1.a
 WHERE t1.pk BETWEEN 5 AND 6 AND t1.b IS NULL OR t1.b = 5
 ORDER BY t1.b;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	SIMPLE	t1	ref	PRIMARY,idx	idx	4	const	2	100.00	Using where; Using filesort
+1	SIMPLE	t1	ref	PRIMARY,idx	idx	4	const	2	100.00	Using where
 1	SIMPLE	t2	ref	c	c	5	test.t1.a	2	100.00	
 Warnings:
-Note	1003	select `test`.`t1`.`b` AS `b`,`test`.`t2`.`c` AS `c`,`test`.`t2`.`d` AS `d` from `test`.`t2` join `test`.`t1` where ((`test`.`t2`.`c` = `test`.`t1`.`a`) and (((`test`.`t1`.`pk` between 5 and 6) and isnull(`test`.`t1`.`b`)) or (`test`.`t1`.`b` = 5))) order by `test`.`t1`.`b`
+Note	1003	select `test`.`t1`.`b` AS `b`,`test`.`t2`.`c` AS `c`,`test`.`t2`.`d` AS `d` from `test`.`t2` join `test`.`t1` where ((`test`.`t2`.`c` = `test`.`t1`.`a`) and (`test`.`t1`.`b` = 5)) order by `test`.`t1`.`b`
 SELECT t1.b, t2.c, t2.d FROM t2 LEFT JOIN t1 ON t2.c = t1.a
 WHERE t1.pk BETWEEN 5 AND 6 AND t1.b IS NULL OR t1.b = 5
 ORDER BY t1.b;