Don't give warnings for empty statements with comments

Docs/manual.texi

@@ -46890,6 +46890,9 @@ not yet 100% confident in this code.
 @appendixsubsec Changes in release 3.23.49
 @itemize @bullet
 @item
+Don't give warning for statement that is only a comment;  This is needed for
+@code{mysqldump --disable-keys} to work.
+@item
 Fixed unlikely caching bug when doing a join without keys. In this case
 the last used field for a table always returned @code{NULL}.
 @item

mysql-test/t/comments.test

@@ -5,7 +5,7 @@
 select 1+2/*hello*/+3;
 select 1 /* long
 multi line comment */;
-!$1065 /* empty query */;
+!$1065 ;
 select 1 /*!32301 +1 */;
 select 1 /*!52301 +1 */;
 select 1--1;
@@ -15,3 +15,4 @@ select 1 --2
 +1;
 select 1 # The rest of the row will be ignored
 ;
+/* line with only comment */;

sql/mysql_priv.h

@@ -158,7 +158,8 @@ void kill_one_thread(THD *thd, ulong id);
 #define OPTION_LOW_PRIORITY_UPDATES	8192
 #define OPTION_WARNINGS		16384
 #define OPTION_AUTO_IS_NULL	32768
-#define OPTION_SAFE_UPDATES	65536L*2
+#define OPTION_FOUND_COMMENT	65536L
+#define OPTION_SAFE_UPDATES	OPTION_FOUND_COMMENT*2
 #define OPTION_BUFFER_RESULT	OPTION_SAFE_UPDATES*2
 #define OPTION_BIN_LOG          OPTION_BUFFER_RESULT*2
 #define OPTION_NOT_AUTO_COMMIT	OPTION_BIN_LOG*2

sql/sql_lex.cc

@@ -734,6 +734,7 @@ int yylex(void *arg)
       return(TEXT_STRING);
 
     case STATE_COMMENT:			//  Comment
+      lex->options|= OPTION_FOUND_COMMENT;
       while ((c = yyGet()) != '\n' && c) ;
       yyUnget();			// Safety against eof
       state = STATE_START;		// Try again
@@ -745,6 +746,7 @@ int yylex(void *arg)
 	break;
       }
       yySkip();				// Skip '*'
+      lex->options|= OPTION_FOUND_COMMENT;
       if (yyPeek() == '!')		// MySQL command in comment
       {
 	ulong version=MYSQL_VERSION_ID;

sql/sql_lex.h

@@ -53,7 +53,7 @@ enum enum_sql_command {
   SQLCOM_BEGIN, SQLCOM_LOAD_MASTER_TABLE, SQLCOM_CHANGE_MASTER,
   SQLCOM_RENAME_TABLE, SQLCOM_BACKUP_TABLE, SQLCOM_RESTORE_TABLE,
   SQLCOM_RESET, SQLCOM_PURGE, SQLCOM_SHOW_BINLOGS,
-  SQLCOM_SHOW_OPEN_TABLES, SQLCOM_DO,
+  SQLCOM_SHOW_OPEN_TABLES, SQLCOM_DO, SQLCOM_EMPTY_QUERY,
   SQLCOM_END
 };
 

sql/sql_parse.cc

@@ -1181,6 +1181,10 @@ mysql_execute_command(void)
     res=mysql_do(thd, *lex->insert_list);
     break;
 
+  case SQLCOM_EMPTY_QUERY:
+    send_ok(&thd->net);
+    break;
+
   case SQLCOM_PURGE:
     {
       if (check_process_priv(thd))

sql/sql_yacc.yy

@@ -544,10 +544,18 @@ bool my_yyoverflow(short **a, YYSTYPE **b,int *yystacksize);
 query:
 	END_OF_INPUT
 	{
-	   if (!current_thd->bootstrap)
+	   THD *thd=current_thd;
+	   if (!thd->bootstrap &&
+	      (!(thd->lex.options & OPTION_FOUND_COMMENT)))
+	   {
 	     send_error(&current_thd->net,ER_EMPTY_QUERY);
 	     YYABORT;
  	   }
+	   else
+	   {
+	     thd->lex.sql_command = SQLCOM_EMPTY_QUERY;
+	   }
+	}
 	| verb_clause END_OF_INPUT {}
 
 verb_clause: