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

into  mysql.com:/home/svoj/devel/mysql/BUG28248/mysql-5.1-engines


mysql-test/r/merge.result:
  Auto merged
mysql-test/t/merge.test:
  Auto merged
storage/myisammrg/ha_myisammrg.cc:
  Auto merged
sql/sql_yacc.yy:
  After merge fix.

4 files changed, 42 insertions, 1 deletions

diff --git a/mysql-test/r/merge.result b/mysql-test/r/merge.result
index a709817b7ef..170cffc13d5 100644
--- a/mysql-test/r/merge.result
+++ b/mysql-test/r/merge.result
@@ -964,6 +964,28 @@ 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
 create table t1 (c1 int, index(c1));
 create table t2 (c1 int, index(c1)) engine=merge union=(t1);
diff --git a/mysql-test/t/merge.test b/mysql-test/t/merge.test
index e49297dd06c..a4602a3b82a 100644
--- a/mysql-test/t/merge.test
+++ b/mysql-test/t/merge.test
@@ -599,6 +599,19 @@ 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
 
diff --git a/sql/sql_yacc.yy b/sql/sql_yacc.yy
index 1bd90e74f47..c8d04bbcb7b 100644
--- a/sql/sql_yacc.yy
+++ b/sql/sql_yacc.yy
@@ -4355,7 +4355,7 @@ create_table_option:
             Lex->create_info.row_type= $3;
             Lex->create_info.used_fields|= HA_CREATE_USED_ROW_FORMAT;
           }
-        | UNION_SYM opt_equal '(' table_list ')'
+        | UNION_SYM opt_equal '(' opt_table_list ')'
           {
             /* Move the union list to the merge_list */
             LEX *lex=Lex;
diff --git a/storage/myisammrg/ha_myisammrg.cc b/storage/myisammrg/ha_myisammrg.cc
index 3fccb91e9b5..7f305061b41 100644
--- a/storage/myisammrg/ha_myisammrg.cc
+++ b/storage/myisammrg/ha_myisammrg.cc
@@ -1102,6 +1102,12 @@ 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=("));
 
   current_db= table->s->db.str;