gap lock is not set if implicit lock exists

commit 1748a31ae8d69e4939336f644f884e9de3039e7f

Author: Marko Mäkelä <marko.makela@mariadb.com>

Date:   Tue Jul 3 15:10:06 2018 +0300

    MDEV-16675 Unnecessary explicit lock acquisition during UPDATE or DELETE

▾ lock_rec_convert_impl_to_expl                                                 

  ▾ lock_clust_rec_read_check_and_lock                                          

    ▾ sel_set_rec_lock                                                          

      ▸ row_search_mvcc

--source include/have_innodb.inc                                                

--source include/count_sessions.inc                                             

CREATE TABLE t(a INT UNSIGNED PRIMARY KEY) ENGINE=InnoDB;                       

INSERT INTO t VALUES (10), (30);                                                

--connect (con1,localhost,root,,)                                               

SET TRANSACTION ISOLATION LEVEL SERIALIZABLE;                                   

BEGIN;                                                                          

INSERT INTO t VALUES (20);                                                      

SELECT * FROM t WHERE a BETWEEN 10 AND 30;                                      

--connection default                                                            

SET session innodb_lock_wait_timeout=1;                                         

--error ER_LOCK_WAIT_TIMEOUT                                                    

INSERT INTO t VALUES (15);                                                      

--disconnect con1                                                               

DROP TABLE t;                                                                   

--source include/wait_until_count_sessions.inc