root@localhost [test]> system cat docs/INFO_SRC
commit: 432d360adedd7d8976fd6254eb3f5bee0b1ac3d6
date: 2017-06-22 16:12:22 +0200
build-date: 2017-06-22 16:13:32 +0200
short: 432d360
branch: mysql-5.7.19-release

MySQL source 5.7.19
[umshastr@hod03]/export/umesh/server/binaries/GABuilds/mysql-5.7.19: wget -O t2.sql https://bugs.mysql.com/file.php?id=25953&bug_id=87947
[umshastr@hod03]/export/umesh/server/binaries/GABuilds/mysql-5.7.19: bin/mysql -uroot -S /tmp/mysql_ushastry.sock test < t2.sql
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[umshastr@hod03]/export/umesh/server/binaries/GABuilds/mysql-5.7.19: bin/mysql -uroot -S /tmp/mysql_ushastry.sock
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 5
Server version: 5.7.19-log MySQL Community Server (GPL)

Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

root@localhost [(none)]> use test
Database changed
root@localhost [test]> SELECT @a:=TIMESTAMPADD(SECOND,3,MIN(b)), @b:=TIMESTAMPADD(SECOND,3,MIN(b)) FROM t2;
+-----------------------------------+-----------------------------------+
| @a:=TIMESTAMPADD(SECOND,3,MIN(b)) | @b:=TIMESTAMPADD(SECOND,3,MIN(b)) |
+-----------------------------------+-----------------------------------+
| 2017-10-09 07:24:16               | 2017-10-09 07:24:16               |
+-----------------------------------+-----------------------------------+
1 row in set (0.00 sec)

root@localhost [test]> SELECT @b:=TIMESTAMPADD(SECOND,1,@b);
+-------------------------------+
| @b:=TIMESTAMPADD(SECOND,1,@b) |
+-------------------------------+
| 2017-10-09 07:24:17           |
+-------------------------------+
1 row in set (0.00 sec)

root@localhost [test]> EXPLAIN SELECT count(*) FROM t2 WHERE b BETWEEN @a AND @b and c=1;
+----+-------------+-------+------------+-------+---------------+------+---------+------+------+----------+------------------------------------+
| id | select_type | table | partitions | type  | possible_keys | key  | key_len | ref  | rows | filtered | Extra                              |
+----+-------------+-------+------------+-------+---------------+------+---------+------+------+----------+------------------------------------+
|  1 | SIMPLE      | t2    | NULL       | range | b,c           | b    | 4       | NULL |   48 |    49.81 | Using index condition; Using where |
+----+-------------+-------+------------+-------+---------------+------+---------+------+------+----------+------------------------------------+
1 row in set, 1 warning (0.00 sec)

root@localhost [test]> SELECT @b:=TIMESTAMPADD(SECOND,1,@b);
+-------------------------------+
| @b:=TIMESTAMPADD(SECOND,1,@b) |
+-------------------------------+
| 2017-10-09 07:24:18           |
+-------------------------------+
1 row in set (0.00 sec)

root@localhost [test]> EXPLAIN SELECT count(*) FROM t2 WHERE b BETWEEN @a AND @b and c=1;
+----+-------------+-------+------------+-------+---------------+------+---------+------+------+----------+------------------------------------+
| id | select_type | table | partitions | type  | possible_keys | key  | key_len | ref  | rows | filtered | Extra                              |
+----+-------------+-------+------------+-------+---------------+------+---------+------+------+----------+------------------------------------+
|  1 | SIMPLE      | t2    | NULL       | range | b,c           | b    | 4       | NULL |  112 |    49.81 | Using index condition; Using where |
+----+-------------+-------+------------+-------+---------------+------+---------+------+------+----------+------------------------------------+
1 row in set, 1 warning (0.00 sec)

root@localhost [test]> SELECT @b:=TIMESTAMPADD(SECOND,1,@b);
+-------------------------------+
| @b:=TIMESTAMPADD(SECOND,1,@b) |
+-------------------------------+
| 2017-10-09 07:24:19           |
+-------------------------------+
1 row in set (0.00 sec)

root@localhost [test]> EXPLAIN SELECT count(*) FROM t2 WHERE b BETWEEN @a AND @b and c=1;
+----+-------------+-------+------------+-------+---------------+------+---------+------+------+----------+------------------------------------+
| id | select_type | table | partitions | type  | possible_keys | key  | key_len | ref  | rows | filtered | Extra                              |
+----+-------------+-------+------------+-------+---------------+------+---------+------+------+----------+------------------------------------+
|  1 | SIMPLE      | t2    | NULL       | range | b,c           | b    | 4       | NULL |  240 |    49.81 | Using index condition; Using where |
+----+-------------+-------+------------+-------+---------------+------+---------+------+------+----------+------------------------------------+
1 row in set, 1 warning (0.00 sec)

root@localhost [test]> SELECT @b:=TIMESTAMPADD(SECOND,1,@b);
+-------------------------------+
| @b:=TIMESTAMPADD(SECOND,1,@b) |
+-------------------------------+
| 2017-10-09 07:24:20           |
+-------------------------------+
1 row in set (0.00 sec)

root@localhost [test]> EXPLAIN SELECT count(*) FROM t2 WHERE b BETWEEN @a AND @b and c=1;
+----+-------------+-------+------------+-------+---------------+------+---------+------+------+----------+------------------------------------+
| id | select_type | table | partitions | type  | possible_keys | key  | key_len | ref  | rows | filtered | Extra                              |
+----+-------------+-------+------------+-------+---------------+------+---------+------+------+----------+------------------------------------+
|  1 | SIMPLE      | t2    | NULL       | range | b,c           | b    | 4       | NULL |  496 |    49.81 | Using index condition; Using where |
+----+-------------+-------+------------+-------+---------------+------+---------+------+------+----------+------------------------------------+
1 row in set, 1 warning (0.00 sec)

root@localhost [test]> SELECT @b:=TIMESTAMPADD(SECOND,1,@b);
+-------------------------------+
| @b:=TIMESTAMPADD(SECOND,1,@b) |
+-------------------------------+
| 2017-10-09 07:24:21           |
+-------------------------------+
1 row in set (0.00 sec)

root@localhost [test]> EXPLAIN SELECT count(*) FROM t2 WHERE b BETWEEN @a AND @b and c=1;
+----+-------------+-------+------------+-------+---------------+------+---------+------+------+----------+------------------------------------+
| id | select_type | table | partitions | type  | possible_keys | key  | key_len | ref  | rows | filtered | Extra                              |
+----+-------------+-------+------------+-------+---------------+------+---------+------+------+----------+------------------------------------+
|  1 | SIMPLE      | t2    | NULL       | range | b,c           | b    | 4       | NULL | 1008 |    49.81 | Using index condition; Using where |
+----+-------------+-------+------------+-------+---------------+------+---------+------+------+----------+------------------------------------+
1 row in set, 1 warning (0.00 sec)

root@localhost [test]> SELECT @b:=TIMESTAMPADD(SECOND,1,@b);
+-------------------------------+
| @b:=TIMESTAMPADD(SECOND,1,@b) |
+-------------------------------+
| 2017-10-09 07:24:22           |
+-------------------------------+
1 row in set (0.00 sec)

root@localhost [test]> EXPLAIN SELECT count(*) FROM t2 WHERE b BETWEEN @a AND @b and c=1;
+----+-------------+-------+------------+------+---------------+------+---------+-------+------+----------+-------------+
| id | select_type | table | partitions | type | possible_keys | key  | key_len | ref   | rows | filtered | Extra       |
+----+-------------+-------+------------+------+---------------+------+---------+-------+------+----------+-------------+
|  1 | SIMPLE      | t2    | NULL       | ref  | b,c           | c    | 5       | const | 8192 |    12.36 | Using where |
+----+-------------+-------+------------+------+---------------+------+---------+-------+------+----------+-------------+
1 row in set, 1 warning (0.00 sec)

root@localhost [test]> SET PROFILING=1;
Query OK, 0 rows affected, 1 warning (0.00 sec)

root@localhost [test]> SELECT count(*) FROM t2 WHERE b BETWEEN @a AND @b and c=1;
+----------+
| count(*) |
+----------+
|     1016 |
+----------+
1 row in set (0.02 sec)

root@localhost [test]> SELECT count(*) FROM t2 WHERE b BETWEEN @a AND @b and c=1;
+----------+
| count(*) |
+----------+
|     1016 |
+----------+
1 row in set (0.02 sec)

root@localhost [test]> SELECT count(*) FROM t2 USE INDEX(b) WHERE b BETWEEN @a AND @b and c=1;
+----------+
| count(*) |
+----------+
|     1016 |
+----------+
1 row in set (0.01 sec)

root@localhost [test]> SELECT count(*) FROM t2 USE INDEX(b) WHERE b BETWEEN @a AND @b and c=1;
+----------+
| count(*) |
+----------+
|     1016 |
+----------+
1 row in set (0.01 sec)

root@localhost [test]> SELECT count(*) FROM t2 USE INDEX(b) WHERE b BETWEEN @a AND @b and c=1;
+----------+
| count(*) |
+----------+
|     1016 |
+----------+
1 row in set (0.01 sec)

root@localhost [test]> SELECT count(*) FROM t2 USE INDEX(c) WHERE b BETWEEN @a AND @b and c=1;
+----------+
| count(*) |
+----------+
|     1016 |
+----------+
1 row in set (0.02 sec)

root@localhost [test]> SELECT count(*) FROM t2 USE INDEX(c) WHERE b BETWEEN @a AND @b and c=1;
+----------+
| count(*) |
+----------+
|     1016 |
+----------+
1 row in set (0.02 sec)

root@localhost [test]> SELECT count(*) FROM t2 USE INDEX(c) WHERE b BETWEEN @a AND @b and c=1;
+----------+
| count(*) |
+----------+
|     1016 |
+----------+
1 row in set (0.02 sec)

root@localhost [test]> SHOW PROFILES;
+----------+------------+------------------------------------------------------------------------+
| Query_ID | Duration   | Query                                                                  |
+----------+------------+------------------------------------------------------------------------+
|        1 | 0.02068525 | SELECT count(*) FROM t2 WHERE b BETWEEN @a AND @b and c=1              |
|        2 | 0.01881450 | SELECT count(*) FROM t2 WHERE b BETWEEN @a AND @b and c=1              |
|        3 | 0.00676325 | SELECT count(*) FROM t2 USE INDEX(b) WHERE b BETWEEN @a AND @b and c=1 |
|        4 | 0.00660050 | SELECT count(*) FROM t2 USE INDEX(b) WHERE b BETWEEN @a AND @b and c=1 |
|        5 | 0.00669725 | SELECT count(*) FROM t2 USE INDEX(b) WHERE b BETWEEN @a AND @b and c=1 |
|        6 | 0.01884250 | SELECT count(*) FROM t2 USE INDEX(c) WHERE b BETWEEN @a AND @b and c=1 |
|        7 | 0.01862300 | SELECT count(*) FROM t2 USE INDEX(c) WHERE b BETWEEN @a AND @b and c=1 |
|        8 | 0.01839775 | SELECT count(*) FROM t2 USE INDEX(c) WHERE b BETWEEN @a AND @b and c=1 |
+----------+------------+------------------------------------------------------------------------+
8 rows in set, 1 warning (0.00 sec)

root@localhost [test]>