Fixed bug mdev-4996.

The fix for bug mdev-4971 not always correctly set the pointers to
inherited multiple equalities in objects of the Item_equal class. 

4 files changed, 57 insertions, 3 deletions

diff --git a/mysql-test/r/subselect2.result b/mysql-test/r/subselect2.result
index a7689c37a0a..2c482408c2b 100644
--- a/mysql-test/r/subselect2.result
+++ b/mysql-test/r/subselect2.result
@@ -198,4 +198,32 @@ a	b
 1	1
 1	3
 DROP TABLE t1, t2, t3;
+#
+# MDEV-4996: degenerate OR formula in WHERE of a subquery
+#
+CREATE TABLE t1 (a int, c1 varchar(1)) ENGINE=MyISAM;
+INSERT INTO t1 VALUES (2,'x'), (8,'d');
+CREATE TABLE t2 (m int, n int, c2 varchar(1)) ENGINE=MyISAM;
+INSERT INTO t2 VALUES (0, 5, 'x'), (1, 4,'p');
+SELECT * FROM t1 WHERE c1 NOT IN ( 
+SELECT t2a.c2 FROM t2 AS t2a, t2 AS t2b, t2 AS t2c 
+WHERE t2c.c2 = t2b.c2 AND ( t2a.m = t2b.n OR 0 ) AND
+( t2b.m != a OR t2b.m = t2a.m ));
+a	c1
+2	x
+8	d
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE c1 NOT IN ( 
+SELECT t2a.c2 FROM t2 AS t2a, t2 AS t2b, t2 AS t2c 
+WHERE t2c.c2 = t2b.c2 AND ( t2a.m = t2b.n OR 0 ) AND
+( t2b.m != a OR t2b.m = t2a.m ));
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+2	DEPENDENT SUBQUERY	t2a	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+2	DEPENDENT SUBQUERY	t2b	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where; Using join buffer (flat, BNL join)
+2	DEPENDENT SUBQUERY	t2c	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where; Using join buffer (incremental, BNL join)
+Warnings:
+Note	1276	Field or reference 'test.t1.a' of SELECT #2 was resolved in SELECT #1
+Note	1003	select `test`.`t1`.`a` AS `a`,`test`.`t1`.`c1` AS `c1` from `test`.`t1` where (not(<expr_cache><`test`.`t1`.`c1`,`test`.`t1`.`a`>(<in_optimizer>(`test`.`t1`.`c1`,<exists>(select `test`.`t2a`.`c2` from `test`.`t2` `t2a` join `test`.`t2` `t2b` join `test`.`t2` `t2c` where (((`test`.`t2b`.`m` <> `test`.`t1`.`a`) or (`test`.`t2b`.`m` = `test`.`t2a`.`m`)) and trigcond(((<cache>(`test`.`t1`.`c1`) = `test`.`t2a`.`c2`) or isnull(`test`.`t2a`.`c2`))) and (`test`.`t2c`.`c2` = `test`.`t2b`.`c2`) and (`test`.`t2b`.`n` = `test`.`t2a`.`m`)) having trigcond(<is_not_null_test>(`test`.`t2a`.`c2`)))))))
+DROP TABLE t1,t2;
 set optimizer_switch=@subselect2_test_tmp;
diff --git a/mysql-test/r/subselect_sj2_mat.result b/mysql-test/r/subselect_sj2_mat.result
index 18e3f6ddd34..bf5b95d2d8f 100644
--- a/mysql-test/r/subselect_sj2_mat.result
+++ b/mysql-test/r/subselect_sj2_mat.result
@@ -1380,7 +1380,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 2	MATERIALIZED	t2	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
 2	MATERIALIZED	t3	hash_ALL	NULL	#hash#$hj	5	test.t2.i2	3	100.00	Using where; Using join buffer (flat, BNLH join)
 Warnings:
-Note	1003	select `test`.`t1`.`i1` AS `i1` from `test`.`t1` semi join (`test`.`t2` join `test`.`t3`) where ((`test`.`t3`.`i3` = `test`.`t2`.`i2`) and (`test`.`t1`.`i1` = `test`.`t2`.`i2`) and (`test`.`t2`.`i2` > 0))
+Note	1003	select `test`.`t1`.`i1` AS `i1` from `test`.`t1` semi join (`test`.`t2` join `test`.`t3`) where ((`test`.`t3`.`i3` = `test`.`t2`.`i2`) and (`test`.`t1`.`i1` = `test`.`t2`.`i2`) and (`test`.`t3`.`i3` > 0))
 SELECT * FROM t1 
 WHERE i1 IN (SELECT i3 FROM t2, t3 WHERE i3 > 0 AND i3 = i2 OR 1=2);
 i1
diff --git a/mysql-test/t/subselect2.test b/mysql-test/t/subselect2.test
index 75cf842fbdb..5d39499d36b 100644
--- a/mysql-test/t/subselect2.test
+++ b/mysql-test/t/subselect2.test
@@ -222,5 +222,28 @@ SELECT * FROM t3
               GROUP BY t1.b);
 DROP TABLE t1, t2, t3;
 
+--echo #
+--echo # MDEV-4996: degenerate OR formula in WHERE of a subquery
+--echo #
+
+CREATE TABLE t1 (a int, c1 varchar(1)) ENGINE=MyISAM;
+INSERT INTO t1 VALUES (2,'x'), (8,'d');
+
+CREATE TABLE t2 (m int, n int, c2 varchar(1)) ENGINE=MyISAM;
+INSERT INTO t2 VALUES (0, 5, 'x'), (1, 4,'p');
+
+SELECT * FROM t1 WHERE c1 NOT IN ( 
+  SELECT t2a.c2 FROM t2 AS t2a, t2 AS t2b, t2 AS t2c 
+    WHERE t2c.c2 = t2b.c2 AND ( t2a.m = t2b.n OR 0 ) AND
+            ( t2b.m != a OR t2b.m = t2a.m ));
+
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE c1 NOT IN ( 
+  SELECT t2a.c2 FROM t2 AS t2a, t2 AS t2b, t2 AS t2c 
+    WHERE t2c.c2 = t2b.c2 AND ( t2a.m = t2b.n OR 0 ) AND
+            ( t2b.m != a OR t2b.m = t2a.m ));
+
+DROP TABLE t1,t2;
+
 set optimizer_switch=@subselect2_test_tmp;
 
diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index 4543176ea5e..20339f8bede 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -13189,7 +13189,6 @@ void propagate_new_equalities(THD *thd, Item *cond,
       Item_cond_and *cond_and= (Item_cond_and *) cond; 
       List<Item_equal> *cond_equalities= &cond_and->cond_equal.current_level;
       cond_and->cond_equal.upper_levels= inherited;
-      inherited= &cond_and->cond_equal;
       if (!cond_equalities->is_empty() && cond_equalities != new_equalities)
       {
         Item_equal *equal_item;
@@ -13214,7 +13213,10 @@ void propagate_new_equalities(THD *thd, Item *cond,
     List_iterator<Item> li(*((Item_cond*) cond)->argument_list());
     while ((item= li++))
     {
-      propagate_new_equalities(thd, item, new_equalities, inherited,
+      COND_EQUAL *new_inherited= and_level && item->type() == Item::COND_ITEM ?
+	                           &((Item_cond_and *) cond)->cond_equal :
+                                   inherited;
+      propagate_new_equalities(thd, item, new_equalities, new_inherited,
                                is_simplifiable_cond);
     }
   }
@@ -13467,6 +13469,7 @@ remove_eq_conds(THD *thd, COND *cond, Item::cond_result *cond_value)
       List_iterator_fast<Item_equal> it(new_equalities);
       while ((equality= it++))
       {
+	equality->upper_levels= cond_equal->upper_levels;
         equality->merge_into_list(cond_equalities, false, false);
         List_iterator_fast<Item_equal> ei(*cond_equalities);
         while ((equality= ei++))