MDEV-6610 Assertion `thd->is_error() || thd->killed' failed in...

MDEV-6610 Assertion `thd->is_error() || thd->killed' failed in mysql_execute_command on executing an SP with repeated CREATE TABLE .. SELECT

the bug was introduced by CREATE OR REPLACE implementation.
CREATE IF NOT EXISTS ... SELECT was returning an error status to the caller,
while sending an ok packet to the user. SP code was not prepared for that
and trusted that error status means an error.

mysql-test/r/sp-bugs2.result

+CREATE TABLE t1 (i INT);
+SET @a = 2;
+CREATE TABLE IF NOT EXISTS t2 (i INT) ENGINE = MyISAM 
+AS SELECT * FROM t1;
+CREATE TABLE IF NOT EXISTS t2 (i INT) ENGINE = MyISAM 
+AS SELECT * FROM t1;
+Warnings:
+Note	1050	Table 't2' already exists
+DROP TABLE t2;
+CREATE PROCEDURE sp()
+BEGIN
+REPEAT 
+CREATE TABLE IF NOT EXISTS t2 (i INT) ENGINE = MyISAM 
+AS SELECT * FROM t1; 
+SET @a = @a - 1; 
+UNTIL @a = 0 
+END REPEAT ;
+END |
+CALL sp();
+Warnings:
+Note	1050	Table 't2' already exists
+DROP PROCEDURE sp;
+DROP TABLE t1, t2;

mysql-test/t/sp-bugs2.test

+#
+# MDEV-6610 Assertion `thd->is_error() || thd->killed' failed in mysql_execute_command on executing an SP with repeated CREATE TABLE .. SELECT
+#
+CREATE TABLE t1 (i INT);
+SET @a = 2; 
+
+CREATE TABLE IF NOT EXISTS t2 (i INT) ENGINE = MyISAM 
+    AS SELECT * FROM t1; 
+CREATE TABLE IF NOT EXISTS t2 (i INT) ENGINE = MyISAM 
+    AS SELECT * FROM t1;
+DROP TABLE t2;
+
+--delimiter |
+CREATE PROCEDURE sp()
+BEGIN
+REPEAT 
+  CREATE TABLE IF NOT EXISTS t2 (i INT) ENGINE = MyISAM 
+      AS SELECT * FROM t1; 
+  SET @a = @a - 1; 
+UNTIL @a = 0 
+END REPEAT ;
+END |
+--delimiter ;
+
+CALL sp();
+
+DROP PROCEDURE sp;
+DROP TABLE t1, t2;
+

sql/sp_head.cc

@@ -3144,7 +3144,10 @@ sp_instr_stmt::execute(THD *thd, uint *nextp)
     thd->query_name_consts= 0;
 
     if (!thd->is_error())
+    {
+      res= 0;
       thd->get_stmt_da()->reset_diagnostics_area();
+    }
   }
   DBUG_RETURN(res || thd->is_error());
 }