MDEV-3875 Wrong result (missing row) on a DISTINCT query with the same subquery in the SELECT list and GROUP BY

fix remove_dup_with_hash_index() and remove_dup_with_compare() to take NULLs into account

1 files changed, 32 insertions, 0 deletions

diff --git a/mysql-test/r/distinct.result b/mysql-test/r/distinct.result
index 99d98d2a9bc..dc3b2fb1b47 100644
--- a/mysql-test/r/distinct.result
+++ b/mysql-test/r/distinct.result
@@ -847,3 +847,35 @@ time(f1)
 00:00:00.000200
 00:00:00.000300
 drop table t1;
+create table t1(i int, g int);
+insert into t1 values (null, 1), (0, 2);
+select distinct i from t1 group by g;
+i
+NULL
+0
+drop table t1;
+create table t1(i int, g blob);
+insert into t1 values (null, 1), (0, 2);
+select distinct i from t1 group by g;
+i
+NULL
+0
+drop table t1;
+create table t1 (a int) engine=myisam;
+insert into t1 values (0),(7);
+create table t2 (b int) engine=myisam;
+insert into t2 values (7),(0),(3);
+create algorithm=temptable view v as
+select distinct (select max(a) from t1 where alias.b = a) as field1 from t2 as alias group by field1;
+select * from v;
+field1
+NULL
+0
+7
+select distinct (select max(a) from t1 where alias.b = a) as field1 from t2 as alias group by field1;
+field1
+NULL
+0
+7
+drop view v;
+drop table t1, t2;