MDEV-4660 SHUTDOWN command

Based on James Briggs contribution.

mysql-test/r/shutdown.result

+create user user1@localhost;
+shutdown;
+ERROR 42000: Access denied; you need (at least one of) the SHUTDOWN privilege(s) for this operation
+shutdown;
+drop user user1@localhost;

mysql-test/t/shutdown.test

+--source include/not_embedded.inc
+#
+# SHUTDOWN statement
+#
+create user user1@localhost;
+
+connect (c1,localhost,user1,,);
+
+--error ER_SPECIFIC_ACCESS_DENIED_ERROR
+shutdown;
+
+connection default;
+disconnect c1;
+
+--let $_server_id= `SELECT @@server_id`
+--let $_expect_file_name= $MYSQLTEST_VARDIR/tmp/mysqld.$_server_id.expect
+--exec echo "wait" > $_expect_file_name
+
+shutdown;
+
+--source include/wait_until_disconnected.inc
+
+--exec echo "restart" > $_expect_file_name
+--enable_reconnect
+--source include/wait_until_connected_again.inc
+
+drop user user1@localhost;
+

sql/mysqld.cc

@@ -3505,6 +3505,7 @@ SHOW_VAR com_status_vars[]= {
   {"show_user_statistics",      (char*) offsetof(STATUS_VAR, com_stat[(uint) SQLCOM_SHOW_USER_STATS]), SHOW_LONG_STATUS},
   {"show_variables",       (char*) offsetof(STATUS_VAR, com_stat[(uint) SQLCOM_SHOW_VARIABLES]), SHOW_LONG_STATUS},
   {"show_warnings",        (char*) offsetof(STATUS_VAR, com_stat[(uint) SQLCOM_SHOW_WARNS]), SHOW_LONG_STATUS},
+  {"shutdown",             (char*) offsetof(STATUS_VAR, com_stat[(uint) SQLCOM_SHUTDOWN]), SHOW_LONG_STATUS},
   {"start_all_slaves",      (char*) offsetof(STATUS_VAR, com_stat[(uint) SQLCOM_SLAVE_ALL_START]), SHOW_LONG_STATUS},
   {"start_slave",          (char*) offsetof(STATUS_VAR, com_stat[(uint) SQLCOM_SLAVE_START]), SHOW_LONG_STATUS},
   {"stmt_close",           (char*) offsetof(STATUS_VAR, com_stmt_close), SHOW_LONG_STATUS},

sql/sql_lex.h

@@ -194,7 +194,7 @@ enum enum_sql_command {
   SQLCOM_SHOW_RELAYLOG_EVENTS, 
   SQLCOM_SHOW_USER_STATS, SQLCOM_SHOW_TABLE_STATS, SQLCOM_SHOW_INDEX_STATS,
   SQLCOM_SHOW_CLIENT_STATS,
-  SQLCOM_SHOW_EXPLAIN,
+  SQLCOM_SHOW_EXPLAIN, SQLCOM_SHUTDOWN,
 
   /*
     When a command is added here, be sure it's also added in mysqld.cc

sql/sql_parse.cc

@@ -3916,6 +3916,17 @@ end_with_restore_list:
                     lex->kill_signal);
     break;
   }
+  case SQLCOM_SHUTDOWN:
+#ifndef EMBEDDED_LIBRARY
+    if (check_global_access(thd,SHUTDOWN_ACL))
+      goto error;
+    kill_mysql();
+    my_ok(thd);
+#else
+    my_error(ER_NOT_SUPPORTED_YET, MYF(0), "embedded server");
+#endif
+    break;
+
 #ifndef NO_EMBEDDED_ACCESS_CHECKS
   case SQLCOM_SHOW_GRANTS:
   {

sql/sql_prepare.cc

@@ -2177,6 +2177,7 @@ static bool check_prepared_statement(Prepared_statement *stmt)
   case SQLCOM_GRANT:
   case SQLCOM_REVOKE:
   case SQLCOM_KILL:
+  case SQLCOM_SHUTDOWN:
     break;
 
   case SQLCOM_PREPARE:

sql/sql_yacc.yy

@@ -789,10 +789,10 @@ bool my_yyoverflow(short **a, YYSTYPE **b, ulong *yystacksize);
 
 %pure_parser                                    /* We have threads */
 /*
-  Currently there are 174 shift/reduce conflicts.
+  Currently there are 196 shift/reduce conflicts.
   We should not introduce new conflicts any more.
 */
-%expect 174
+%expect 196
 
 /*
    Comments for TOKENS.
@@ -1816,6 +1816,7 @@ statement:
         | set
         | signal_stmt
         | show
+        | shutdown
         | slave
         | start
         | truncate
@@ -12217,6 +12218,11 @@ kill_expr:
           }
         ;
 
+
+shutdown:
+        SHUTDOWN { Lex->sql_command= SQLCOM_SHUTDOWN; }
+        ;
+
 /* change database */
 
 use: