4 files changed, 78 insertions, 1 deletions

diff --git a/mysql-test/r/range.result b/mysql-test/r/range.result
index 6a3850c0ed9..f1f949acd3b 100644
--- a/mysql-test/r/range.result
+++ b/mysql-test/r/range.result
@@ -3201,5 +3201,29 @@ pk	i	v	a	b
 2	2	4	2	4
 drop table t1, t2;
 #
+# MDEV-26553: Always FALSE/NULL disjunct on top level of WHERE is removed
+#
+create table t1 (a int, b int, index idx(a,b));
+insert into t1 values (1,1), (1,2), (2,1), (2,2), (3,3);
+create table t2 (c int);
+insert into t2 values (5), (2), (3), (4);
+select 1 from t1 s1
+where 1 not in (select 1 from t1
+where ((a = 1 or a = 2) and b = 1) or (b > 5 and b < 1));
+1
+select 1 from t1 s1
+where 1 not in (select 1 from t1
+where ((a = 1 or a = 2) and b = 1) or b = NULL);
+1
+select c from t2
+where 2 not in (select 1 from t1
+where ((a=1 or a=2) and b = 1) or (b > 5 and b < 1));
+c
+5
+2
+3
+4
+drop table t1,t2;
+#
 # End of 10.2 tests
 #
diff --git a/mysql-test/r/range_mrr_icp.result b/mysql-test/r/range_mrr_icp.result
index 24f42f34ce5..645576fbe42 100644
--- a/mysql-test/r/range_mrr_icp.result
+++ b/mysql-test/r/range_mrr_icp.result
@@ -3213,6 +3213,30 @@ pk	i	v	a	b
 2	2	4	2	4
 drop table t1, t2;
 #
+# MDEV-26553: Always FALSE/NULL disjunct on top level of WHERE is removed
+#
+create table t1 (a int, b int, index idx(a,b));
+insert into t1 values (1,1), (1,2), (2,1), (2,2), (3,3);
+create table t2 (c int);
+insert into t2 values (5), (2), (3), (4);
+select 1 from t1 s1
+where 1 not in (select 1 from t1
+where ((a = 1 or a = 2) and b = 1) or (b > 5 and b < 1));
+1
+select 1 from t1 s1
+where 1 not in (select 1 from t1
+where ((a = 1 or a = 2) and b = 1) or b = NULL);
+1
+select c from t2
+where 2 not in (select 1 from t1
+where ((a=1 or a=2) and b = 1) or (b > 5 and b < 1));
+c
+5
+2
+3
+4
+drop table t1,t2;
+#
 # End of 10.2 tests
 #
 set optimizer_switch=@mrr_icp_extra_tmp;
diff --git a/mysql-test/t/range.test b/mysql-test/t/range.test
index 890377ed977..7369b9d8a16 100644
--- a/mysql-test/t/range.test
+++ b/mysql-test/t/range.test
@@ -2232,6 +2232,29 @@ select * from t1 inner join t2 on ( t2.b = t1.v or t2.a = t1.pk);
 drop table t1, t2;
 
 --echo #
---echo # End of 10.2 tests
+--echo # MDEV-26553: Always FALSE/NULL disjunct on top level of WHERE is removed
 --echo #
 
+create table t1 (a int, b int, index idx(a,b));
+insert into t1 values (1,1), (1,2), (2,1), (2,2), (3,3);
+
+create table t2 (c int);
+insert into t2 values (5), (2), (3), (4);
+
+select 1 from t1 s1
+  where 1 not in (select 1 from t1
+                    where ((a = 1 or a = 2) and b = 1) or (b > 5 and b < 1));
+
+select 1 from t1 s1
+  where 1 not in (select 1 from t1
+                    where ((a = 1 or a = 2) and b = 1) or b = NULL);
+
+select c from t2
+  where 2 not in (select 1 from t1
+                    where ((a=1 or a=2) and b = 1) or (b > 5 and b < 1));
+
+drop table t1,t2;
+
+--echo #
+--echo # End of 10.2 tests
+--echo #
diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index 54a2facfe9f..47422116e38 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -4504,7 +4504,13 @@ make_join_statistics(JOIN *join, List<TABLE_LIST> &tables_list,
         if (*s->on_expr_ref)
           *s->on_expr_ref= select->cond;
         else
+	{
           join->conds= select->cond;
+          if (join->conds && join->conds->type() == Item::COND_ITEM &&
+              ((Item_cond*) (join->conds))->functype() ==
+              Item_func::COND_AND_FUNC)
+            join->cond_equal= &((Item_cond_and*) (join->conds))->m_cond_equal;
+        }
 
         s->quick=select->quick;
         s->needed_reg=select->needed_reg;