Backport into build-200906240007-5.1.34sp1

> ------------------------------------------------------------
> revno: 2857.1.8
> revision-id: sergey.glukhov@sun.com-20090417084627-yvt63k51vvvjbx9j
> parent: anurag.shekhar@sun.com-20090417055354-7vw80v1rwn0z1tt4
> parent: sergey.glukhov@sun.com-20090417074115-dv9h5ijalj2hgq3r
> committer: Sergey Glukhov <Sergey.Glukhov@sun.com>
> branch nick: mysql-5.1-bugteam
> timestamp: Fri 2009-04-17 13:46:27 +0500
> message:
>   5.0-bugteam->5.1-bugteam merge
>     ------------------------------------------------------------
>     revno: 1810.3882.12
>     revision-id: sergey.glukhov@sun.com-20090417074115-dv9h5ijalj2hgq3r
>     parent: patrick.crews@sun.com-20090416174744-u9fxu6ophud91a1h
>     committer: Sergey Glukhov <Sergey.Glukhov@sun.com>
>     branch nick: mysql-5.0-bugteam
>     timestamp: Fri 2009-04-17 12:41:15 +0500
>     message:
>       Bug#44151 using handler commands on information_schema tables crashes server
>       information schema tables are based on internal tmp tables which are removed
>       after each statement execution. So HANDLER comands can not be used with
>       information schema.

mysql-test/include/handler.inc

@@ -720,3 +720,11 @@ connection con1;
 drop table t1;
 disconnect con1;
 connection default;
+
+#
+# Bug#44151 using handler commands on information_schema tables crashes server
+#
+USE information_schema;
+--error ER_WRONG_USAGE
+HANDLER COLUMNS OPEN;
+USE test;

mysql-test/r/handler_innodb.result

@@ -739,3 +739,7 @@ handler t1 read a next;
 ERROR HY000: Table storage engine for 't1' doesn't have this option
 handler t1 close;
 drop table t1;
+USE information_schema;
+HANDLER COLUMNS OPEN;
+ERROR HY000: Incorrect usage of HANDLER OPEN and information_schema
+USE test;

mysql-test/r/handler_myisam.result

@@ -737,3 +737,7 @@ handler t1 read a next;
 ERROR HY000: Table storage engine for 't1' doesn't have this option
 handler t1 close;
 drop table t1;
+USE information_schema;
+HANDLER COLUMNS OPEN;
+ERROR HY000: Incorrect usage of HANDLER OPEN and information_schema
+USE test;

sql/sql_handler.cc

@@ -199,6 +199,14 @@ bool mysql_ha_open(THD *thd, TABLE_LIST *tables, bool reopen)
                       tables->db, tables->table_name, tables->alias,
                       (int) reopen));
 
+  if (tables->schema_table)
+  {
+    my_error(ER_WRONG_USAGE, MYF(0), "HANDLER OPEN",
+             INFORMATION_SCHEMA_NAME.str);
+    DBUG_PRINT("exit",("ERROR"));
+    DBUG_RETURN(TRUE);
+  }
+
   if (! hash_inited(&thd->handler_tables_hash))
   {
     /*