MDEV-4468 Assertion `error != 0' fails or timeout occurs on select from a...

MDEV-4468 Assertion `error != 0' fails or timeout occurs on select from a FEDERATED table which points at a non-existent table

Federated uses SHOW TABLE STATUS LIKE for ::info().
For nonexisting remote table it doesn't fail, but returns an empty result set.
We need to fake the error in the handler.

mysql-test/suite/federated/federated.result

@@ -7,6 +7,12 @@ Level	Code	Message
 Error	1	server name: 'non_existing' doesn't exist!
 Error	1	Can't create/write to file 'non_existing' (Errcode: 14)
 Error	1005	Can't create table 'test.t1' (errno: 1)
+create table t1 (a int);
+create table fed (a int) engine=Federated CONNECTION='mysql://root@127.0.0.1:MASTER_PORT/test/t1';
+drop table t1;
+select * from fed;
+Got one of the listed errors
+drop table fed;
 DROP TABLE IF EXISTS federated.t1;
 DROP DATABASE IF EXISTS federated;
 DROP TABLE IF EXISTS federated.t1;

mysql-test/suite/federated/federated.test

@@ -8,5 +8,17 @@ connection master;
 CREATE TABLE t1 (a INT) ENGINE=FEDERATED CONNECTION='non_existing';
 SHOW WARNINGS;
 
+#
+# MDEV-4468 Assertion `error != 0' fails or timeout occurs on select from a FEDERATED table which points at a non-existent table
+#
+
+create table t1 (a int);
+--replace_result $MASTER_MYPORT MASTER_PORT
+eval create table fed (a int) engine=Federated CONNECTION='mysql://root@127.0.0.1:$MASTER_MYPORT/test/t1';
+drop table t1;
+--error 1146,1431
+select * from fed;
+drop table fed;
+
 source include/federated_cleanup.inc;
 

storage/federatedx/federatedx_io_mysql.cc

@@ -599,6 +599,11 @@ bool federatedx_io_mysql::table_metadata(ha_statistics *stats,
   return 0;
 
 error:
+  if (!mysql_errno(&mysql))
+  {
+    mysql.net.last_errno= ER_NO_SUCH_TABLE;
+    strmake_buf(mysql.net.last_error, "Remote table does not exist");
+  }
   free_result(result);
   return 1;
 }