Make sure we can use local_seqno provided by MySQL as correct

seqno to start replication.

Author: janlindstrom

mysql-test/suite/galera/r/galera_var_wsrep_start_position.result

@@ -157,7 +157,13 @@ SET @@global.wsrep_start_position='12345678-1234-1234-1234-123456789012:100,1-1-
 ERROR 42000: Variable 'wsrep_start_position' can't be set to the value of '12345678-1234-1234-1234-123456789012:100,1-1-20/abcdefghijklmn'
 SHOW WARNINGS;
 Level	Code	Message
+Warning	1231	wsrep_start_position incorrect 'abcdefghijklmn', local_seqno incorrect
 Error	1231	Variable 'wsrep_start_position' can't be set to the value of '12345678-1234-1234-1234-123456789012:100,1-1-20/abcdefghijklmn'
+SET @@global.wsrep_start_position='64de8141-7bf8-11f0-a5e1-2f107ecf09fa:8410/8502/11/57df8fe9-7bf8-11f0-83b8-00e04ca2f8fe';
+ERROR 42000: Variable 'wsrep_start_position' can't be set to the value of '64de8141-7bf8-11f0-a5e1-2f107ecf09fa:8410/8502/11/57df8fe9-7bf8-11f0-83b8-00e04ca2f8fe'
+SHOW WARNINGS;
+Level	Code	Message
+Error	1231	Variable 'wsrep_start_position' can't be set to the value of '64de8141-7bf8-11f0-a5e1-2f107ecf09fa:8410/8502/11/57df8fe9-7bf8-11f0-83b8-00e04ca2f8fe'
 
 # restore the initial value
 SET @@global.wsrep_start_position = @wsrep_start_position_global_saved;

mysql-test/suite/galera/t/galera_var_wsrep_start_position.test

@@ -109,6 +109,10 @@ SHOW WARNINGS;
 --error ER_WRONG_VALUE_FOR_VAR
 SET @@global.wsrep_start_position='12345678-1234-1234-1234-123456789012:100,1-1-20/abcdefghijklmn';
 SHOW WARNINGS;
+# correct format but wrong position
+--error ER_WRONG_VALUE_FOR_VAR
+SET @@global.wsrep_start_position='64de8141-7bf8-11f0-a5e1-2f107ecf09fa:8410/8502/11/57df8fe9-7bf8-11f0-83b8-00e04ca2f8fe';
+SHOW WARNINGS;
 
 --echo
 --echo # restore the initial value

sql/wsrep_var.cc

@@ -321,9 +321,25 @@ bool wsrep_start_position_verify (THD* thd, const char* start_str)
 
   // Remaining string was seqno.
   if (*endptr == '\0' || *endptr == '/') {
-    /* In migration MySQL 8.x start position can have additional info */
+    /* In migration MySQL 8.x start position can have additional info
+     i.e. local_seqno */
     if (*endptr == '/')
-      *endptr= '\0';
+    {
+      endptr++;
+      startptr= endptr;
+      uint64_t local_seqno __attribute__((unused))
+        (parse_value<uint64_t>(&startptr, &endptr));
+      if (*endptr != '/')
+      {
+        push_warning_printf(thd, Sql_condition::WARN_LEVEL_WARN,
+                          ER_WRONG_VALUE_FOR_VAR,
+                          "wsrep_start_position incorrect '%s'"
+                          ", local_seqno incorrect",
+                          endptr);
+        return true;
+      }
+	
+    }
     return false;
   }
 
@@ -345,7 +361,16 @@ bool wsrep_set_local_position(THD* thd, const char* const value,
   wsrep_uuid_t uuid;
   size_t const uuid_len= wsrep_uuid_scan(value, length, &uuid);
   startptr= (char *)value + uuid_len + 1;
-  wsrep_seqno_t const seqno= parse_value<uint64_t>(&startptr, &endptr);
+  wsrep_seqno_t seqno= parse_value<uint64_t>(&startptr, &endptr);
+
+  /* If this start position is from MySQL we read local_seqno because
+     it is the correct position to start. */
+  if (*startptr == '/')
+  {
+    startptr++;
+    wsrep_seqno_t local_seqno= parse_value<uint64_t>(&startptr, &endptr);
+    seqno= local_seqno;
+  }
 
   if (*startptr == ',')
   {