Merge mysql.com:/home/svoj/devel/bk/mysql-5.0-engines

into  mysql.com:/home/svoj/devel/mysql/BUG28248/mysql-5.0-engines

mysql-test/r/merge.result

@@ -918,4 +918,26 @@ id	ref
 3	2
 4	5
 DROP TABLE t1, t2, t3;
+CREATE TABLE t1(a INT);
+CREATE TABLE m1(a INT) ENGINE=MERGE;
+SHOW CREATE TABLE m1;
+Table	Create Table
+m1	CREATE TABLE `m1` (
+  `a` int(11) default NULL
+) ENGINE=MRG_MyISAM DEFAULT CHARSET=latin1
+DROP TABLE m1;
+CREATE TABLE m1(a INT) ENGINE=MERGE UNION=();
+SHOW CREATE TABLE m1;
+Table	Create Table
+m1	CREATE TABLE `m1` (
+  `a` int(11) default NULL
+) ENGINE=MRG_MyISAM DEFAULT CHARSET=latin1
+ALTER TABLE m1 UNION=(t1);
+ALTER TABLE m1 UNION=();
+SHOW CREATE TABLE m1;
+Table	Create Table
+m1	CREATE TABLE `m1` (
+  `a` int(11) default NULL
+) ENGINE=MRG_MyISAM DEFAULT CHARSET=latin1
+DROP TABLE t1, m1;
 End of 5.0 tests

mysql-test/t/merge.test

@@ -542,5 +542,18 @@ SELECT * FROM t3;
 
 DROP TABLE t1, t2, t3;
 
+#
+# BUG#28248 - mysqldump results with MERGE ... UNION=() cannot be executed
+#
+CREATE TABLE t1(a INT);
+CREATE TABLE m1(a INT) ENGINE=MERGE;
+SHOW CREATE TABLE m1;
+DROP TABLE m1;
+CREATE TABLE m1(a INT) ENGINE=MERGE UNION=();
+SHOW CREATE TABLE m1;
+ALTER TABLE m1 UNION=(t1);
+ALTER TABLE m1 UNION=();
+SHOW CREATE TABLE m1;
+DROP TABLE t1, m1;
 
 --echo End of 5.0 tests

sql/ha_myisammrg.cc

@@ -602,6 +602,12 @@ void ha_myisammrg::append_create_info(String *packet)
     packet->append(STRING_WITH_LEN(" INSERT_METHOD="));
     packet->append(get_type(&merge_insert_method,file->merge_insert_method-1));
   }
+  /*
+    There is no sence adding UNION clause in case there is no underlying
+    tables specified.
+  */
+  if (file->open_tables == file->end_table)
+    return;
   packet->append(STRING_WITH_LEN(" UNION=("));
   MYRG_TABLE *open_table,*first;
 

sql/sql_yacc.yy

@@ -2932,7 +2932,7 @@ create_table_option:
 	    my_error(ER_WARN_DEPRECATED_SYNTAX, MYF(0), "RAID_CHUNKSIZE", "PARTITION");
 	    MYSQL_YYABORT;
 	  }
-	| UNION_SYM opt_equal '(' table_list ')'
+	| UNION_SYM opt_equal '(' opt_table_list ')'
 	  {
 	    /* Move the union list to the merge_list */
 	    LEX *lex=Lex;