BUG#32803050 REPLICA WITH FEDERATED TABLE CRASHES IN HA_FEDERATED::RND_POS WHEN APPLYING ROW EVENTS

Description: When executing Update/Delete with indexes on a table with
Row based replication setup and the federated table on slave, The Slave
crashes.

Analysis: Slave crashes when trying to get the reference to the row
to be update or deleted on federated table using position() method.
The crash occurs due to assert(stored_result) in position method, since
the stored_result is still empty. Server should do index_scan and
update the stored_result and then call for position() and ha_rnd_pos()
methods to get the ref to the row stored. But in this scenario the
server calls for position() method without scanning the table resulting
in crash at assert.

Fix: The fix is added to fetch the position or reference of the row
only when stored_result is not empty.

RB: 26755

Author: salmankhan123417

storage/federated/ha_federated.cc

@@ -3455,6 +3455,23 @@ int ha_federated::execute_simple_query(const char *query, int len)
   DBUG_RETURN(0);
 }
 
+
+int ha_federated::rnd_pos_by_record(uchar *record) {
+  int error;
+  assert(table_flags() & HA_PRIMARY_KEY_REQUIRED_FOR_POSITION);
+
+  error = ha_rnd_init(false);
+  if (error != 0) return error;
+
+  if (stored_result) {
+    position(record);
+    error = ha_rnd_pos(record, ref);
+  }
+
+  ha_rnd_end();
+  return error;
+}
+
 struct st_mysql_storage_engine federated_storage_engine=
 { MYSQL_HANDLERTON_INTERFACE_VERSION };
 

storage/federated/ha_federated.h

@@ -278,5 +278,6 @@ class ha_federated: public handler
   int connection_autocommit(bool state);
   int execute_simple_query(const char *query, int len);
   int reset(void);
+  int rnd_pos_by_record(uchar *record);
 };