Backport of

  - revid:sp1r-svoj@mysql.com/june.mysql.com-20080324111246-00461
  - revid:sp1r-svoj@mysql.com/june.mysql.com-20080414125521-40866

  BUG#35274 - merge table doesn't need any base tables, gives
              error 124 when key accessed

  SELECT queries that use index against a merge table with empty
  underlying tables list may return with error "Got error 124 from
  storage engine".

  The problem was that wrong error being returned.

mysql-test/r/merge.result

@@ -277,7 +277,7 @@ t3	CREATE TABLE `t3` (
 drop table t3,t2,t1;
 create table t1 (a int not null, key(a)) engine=merge;
 select * from t1;
-ERROR HY000: Got error 124 from storage engine
+a
 drop table t1;
 create table t1 (a int not null, b int not null, key(a,b));
 create table t2 (a int not null, b int not null, key(a,b));
@@ -988,6 +988,11 @@ m1	CREATE TABLE `m1` (
   `a` int(11) DEFAULT NULL
 ) ENGINE=MRG_MyISAM DEFAULT CHARSET=latin1
 DROP TABLE t1, m1;
+CREATE TABLE t1(a INT, KEY(a)) ENGINE=merge;
+SELECT MAX(a) FROM t1;
+MAX(a)
+NULL
+DROP TABLE t1;
 CREATE TABLE t1(a INT);
 CREATE TABLE t2(a VARCHAR(10));
 CREATE TABLE m1(a INT) ENGINE=MERGE UNION=(t1, t2);

mysql-test/t/merge.test

@@ -126,7 +126,6 @@ drop table t3,t2,t1;
 # Test table without unions
 #
 create table t1 (a int not null, key(a)) engine=merge;
---error 1030
 select * from t1;
 drop table t1;
 
@@ -615,6 +614,14 @@ ALTER TABLE m1 UNION=();
 SHOW CREATE TABLE m1;
 DROP TABLE t1, m1;
 
+#
+# BUG#35274 - merge table doesn't need any base tables, gives error 124 when
+#             key accessed
+#
+CREATE TABLE t1(a INT, KEY(a)) ENGINE=merge;
+SELECT MAX(a) FROM t1;
+DROP TABLE t1;
+
 #
 # BUG#32047 - 'Spurious' errors while opening MERGE tables
 #

storage/myisammrg/myrg_queue.c

@@ -65,7 +65,17 @@ int _myrg_init_queue(MYRG_INFO *info,int inx,enum ha_rkey_function search_flag)
     }
   }
   else
-    my_errno= error= HA_ERR_WRONG_INDEX;
+  {
+    /*
+      inx may be bigger than info->keys if there are no underlying tables
+      defined. In this case we should return empty result. As we check for
+      underlying tables conformance when we open a table, we may not enter
+      this branch with underlying table that has less keys than merge table
+      have.
+    */
+    DBUG_ASSERT(!info->tables);
+    error= my_errno= HA_ERR_END_OF_FILE;
+  }
   return error;
 }