Bug #17766: The server accepts to create MERGE tables which cannot work

 Changed the error reporting (and a crash) when inserting data into a
 MERGE table that has no underlying tables or no INSERT_METHOD specified
 by reporting that it is read-only.

include/my_base.h

@@ -347,8 +347,9 @@ enum ha_base_keytype {
 #define HA_ERR_NULL_IN_SPATIAL   158  /* NULLs are not supported in spatial index */
 #define HA_ERR_TABLE_DEF_CHANGED 159  /* The table changed in storage engine */
 #define HA_ERR_TABLE_NEEDS_UPGRADE 160  /* The table changed in storage engine */
+#define HA_ERR_TABLE_READONLY    161  /* The table is not writable */
 
-#define HA_ERR_LAST              160  /*Copy last error nr.*/
+#define HA_ERR_LAST              161  /*Copy last error nr.*/
 /* Add error numbers before HA_ERR_LAST and change it accordingly. */
 #define HA_ERR_ERRORS            (HA_ERR_LAST - HA_ERR_FIRST + 1)
 

mysql-test/r/merge.result

@@ -782,3 +782,15 @@ create table tm (b bit(1)) engine = merge union = (t1,t2);
 select * from tm;
 b
 drop table tm, t1, t2;
+create table t1 (a int) insert_method = last engine = merge;
+insert into t1 values (1);
+ERROR HY000: Table 't1' is read only
+create table t2 (a int) engine = myisam;
+alter table t1 union (t2);
+insert into t1 values (1);
+alter table t1 insert_method = no;
+insert into t1 values (1);
+ERROR HY000: Table 't1' is read only
+drop table t2;
+drop table t1;
+End of 5.0 tests

mysql-test/t/merge.test

@@ -399,4 +399,19 @@ create table tm (b bit(1)) engine = merge union = (t1,t2);
 select * from tm;
 drop table tm, t1, t2;
 
-# End of 5.0 tests
+#
+# Bug #17766: The server accepts to create MERGE tables which cannot work
+#
+create table t1 (a int) insert_method = last engine = merge;
+--error ER_OPEN_AS_READONLY
+insert into t1 values (1);
+create table t2 (a int) engine = myisam;
+alter table t1 union (t2);
+insert into t1 values (1);
+alter table t1 insert_method = no;
+--error ER_OPEN_AS_READONLY
+insert into t1 values (1);
+drop table t2;
+drop table t1;
+
+--echo End of 5.0 tests

sql/ha_myisammrg.cc

@@ -132,6 +132,10 @@ int ha_myisammrg::close(void)
 int ha_myisammrg::write_row(byte * buf)
 {
   statistic_increment(table->in_use->status_var.ha_write_count,&LOCK_status);
+
+  if (file->merge_insert_method == MERGE_INSERT_DISABLED || !file->tables)
+    return (HA_ERR_TABLE_READONLY);
+
   if (table->timestamp_field_type & TIMESTAMP_AUTO_SET_ON_INSERT)
     table->timestamp_field->set_time();
   if (table->next_number_field && buf == table->record[0])

sql/handler.cc

@@ -426,6 +426,7 @@ static int ha_init_errors(void)
   SETMSG(HA_ERR_NO_CONNECTION,          "Could not connect to storage engine");
   SETMSG(HA_ERR_TABLE_DEF_CHANGED,      ER(ER_TABLE_DEF_CHANGED));
   SETMSG(HA_ERR_TABLE_NEEDS_UPGRADE,    ER(ER_TABLE_NEEDS_UPGRADE));
+  SETMSG(HA_ERR_TABLE_READONLY,         ER(ER_OPEN_AS_READONLY));
 
   /* Register the error messages for use with my_error(). */
   return my_error_register(errmsgs, HA_ERR_FIRST, HA_ERR_LAST);
@@ -1799,6 +1800,9 @@ void handler::print_error(int error, myf errflag)
   case HA_ERR_TABLE_NEEDS_UPGRADE:
     textno=ER_TABLE_NEEDS_UPGRADE;
     break;
+  case HA_ERR_TABLE_READONLY:
+    textno= ER_OPEN_AS_READONLY;
+    break;
   default:
     {
       /* The error was "unknown" to this function.