MySQL xpath concatenation operator, how to add space?

Question

This does what I expect:

mysql> select ExtractValue("<x><a>1</a><b>2</b></x>", "concat(/x/a, /x/b)");
+---------------------------------------------------------------+
| ExtractValue("<x><a>1</a><b>2</b></x>", "concat(/x/a, /x/b)") |
+---------------------------------------------------------------+
| 12                                                            |
+---------------------------------------------------------------+
1 row in set (0.00 sec)

But why does this return "1" instead of "1 2"?

mysql> select ExtractValue("<x><a>1</a><b>2</b></x>", "concat(/x/a, ' ', /x/b)");
+--------------------------------------------------------------------+
| ExtractValue("<x><a>1</a><b>2</b></x>", "concat(/x/a, ' ', /x/b)") |
+--------------------------------------------------------------------+
| 1                                                                  |
+--------------------------------------------------------------------+
1 row in set (0.00 sec)

Answer 1

This is a verified error. The MySQL xpath concatenation operator only considers the first 2 parameters, when it must consider all parameters.

https://bugs.mysql.com/bug.php?id=71704

As a workaround, you can select individual values ​​and pass them to a regular function concat:

select concat(ExtractValue("<x><a>1</a><b>2</b></x>", "/x/a"),' ',
  ExtractValue("<x><a>1</a><b>2</b></x>", "/x/b"));

Answer 2

Improvement detected:

mysql> select ExtractValue("<x><a>1</a><b>2</b></x>", "concat(/x/a, concat(' ', /x/b))");
+----------------------------------------------------------------------------+
| ExtractValue("<x><a>1</a><b>2</b></x>", "concat(/x/a, concat(' ', /x/b))") |
+----------------------------------------------------------------------------+
| 1 2                                                                        |
+----------------------------------------------------------------------------+
1 row in set (0.00 sec)