Remove unused ha_innobase::lock

In MySQL 5.7, a follow-up to WL#6671 removed the unused
fields ha_innobase::lock and INNOBASE_SHARE::lock, but
MariaDB did not remove them, even though a counterpart of
WL#6671 itself was implemented as MDEV-7660 in
commit d665e79.

INNOBASE_SHARE was removed in MDEV-16557. Thus, all that
needs to be removed is the unused member ha_innobase::lock
and related code.

Thanks to Monty (and Valgrind) for noticing that
ha_innobase::lock was uninitialized.

storage/innobase/handler/ha_innodb.cc

@@ -16523,73 +16523,6 @@ ha_innobase::store_lock(
 		m_prebuilt->stored_select_lock_type = LOCK_NONE;
 	}
 
-	if (lock_type != TL_IGNORE && lock.type == TL_UNLOCK) {
-
-		/* Starting from 5.0.7, we weaken also the table locks
-		set at the start of a MySQL stored procedure call, just like
-		we weaken the locks set at the start of an SQL statement.
-		MySQL does set in_lock_tables TRUE there, but in reality
-		we do not need table locks to make the execution of a
-		single transaction stored procedure call deterministic
-		(if it does not use a consistent read). */
-
-		if (lock_type == TL_READ
-		    && sql_command == SQLCOM_LOCK_TABLES) {
-			/* We come here if MySQL is processing LOCK TABLES
-			... READ LOCAL. MyISAM under that table lock type
-			reads the table as it was at the time the lock was
-			granted (new inserts are allowed, but not seen by the
-			reader). To get a similar effect on an InnoDB table,
-			we must use LOCK TABLES ... READ. We convert the lock
-			type here, so that for InnoDB, READ LOCAL is
-			equivalent to READ. This will change the InnoDB
-			behavior in mysqldump, so that dumps of InnoDB tables
-			are consistent with dumps of MyISAM tables. */
-
-			lock_type = TL_READ_NO_INSERT;
-		}
-
-		/* If we are not doing a LOCK TABLE, DISCARD/IMPORT
-		TABLESPACE or TRUNCATE TABLE then allow multiple
-		writers. Note that ALTER TABLE uses a TL_WRITE_ALLOW_READ
-		< TL_WRITE_CONCURRENT_INSERT.
-
-		We especially allow multiple writers if MySQL is at the
-		start of a stored procedure call (SQLCOM_CALL) or a
-		stored function call (MySQL does have in_lock_tables
-		TRUE there). */
-
-		if ((lock_type >= TL_WRITE_CONCURRENT_INSERT
-		     && lock_type <= TL_WRITE)
-		    && !(in_lock_tables
-			 && sql_command == SQLCOM_LOCK_TABLES)
-		    && !thd_tablespace_op(thd)
-		    && sql_command != SQLCOM_TRUNCATE
-		    && sql_command != SQLCOM_OPTIMIZE
-		    && sql_command != SQLCOM_CREATE_TABLE) {
-
-			lock_type = TL_WRITE_ALLOW_WRITE;
-		}
-
-		/* In queries of type INSERT INTO t1 SELECT ... FROM t2 ...
-		MySQL would use the lock TL_READ_NO_INSERT on t2, and that
-		would conflict with TL_WRITE_ALLOW_WRITE, blocking all inserts
-		to t2. Convert the lock to a normal read lock to allow
-		concurrent inserts to t2.
-
-		We especially allow concurrent inserts if MySQL is at the
-		start of a stored procedure call (SQLCOM_CALL)
-		(MySQL does have thd_in_lock_tables() TRUE there). */
-
-		if (lock_type == TL_READ_NO_INSERT
-		    && sql_command != SQLCOM_LOCK_TABLES) {
-
-			lock_type = TL_READ;
-		}
-
-		lock.type = lock_type;
-	}
-
 	if (!trx_is_started(trx)
 	    && (m_prebuilt->select_lock_type != LOCK_NONE
 	        || m_prebuilt->stored_select_lock_type != LOCK_NONE)) {

storage/innobase/handler/ha_innodb.h

@@ -461,8 +461,6 @@ class ha_innobase: public handler
 	this is set in external_lock function */
 	THD*			m_user_thd;
 
-	THR_LOCK_DATA	lock;
-
 	/** buffer used in updates */
 	uchar*			m_upd_buf;