Delete data from tablespace

[Markus Fladischer]

I have a mysql-cluster 7.1.10 (using NDBD) running and I use tablespaces to save one of my tables to disk. I created the table space and altered the appropriate table to use the tablespace. To see if the tablespace is used:

mysql> SELECT FILE_NAME, (FREE_EXTENTS*EXTENT_SIZE) AS FREE_SPACE, (TOTAL_EXTENTS*EXTENT_SIZE) AS TOTAL_SPACE, EXTRA FROM information_schema.FILES WHERE FILE_TYPE = 'DATAFILE';

OUTPUT:
+---------------------+------------+-------------+----------------+
| FILE_NAME | FREE_SPACE | TOTAL_SPACE | EXTRA |
+---------------------+------------+-------------+----------------+
| data_cmn_free_1.dat | 4294967296 | 4294967296 | CLUSTER_NODE=4 |
| data_cmn_free_1.dat | 4294967296 | 4294967296 | CLUSTER_NODE=5 |
| data_cmn_free_1.dat | 4294967296 | 4294967296 | CLUSTER_NODE=6 |
+---------------------+------------+-------------+----------------+
3 rows in set (0.00 sec)

After a while there is some data in the table so I check again if the tablespace is used correctly (same query): FREE_SPACE switches from 4294967296 to 4093640704

+---------------------+------------+-------------+----------------+
| FILE_NAME | FREE_SPACE | TOTAL_SPACE | EXTRA |
+---------------------+------------+-------------+----------------+
| data_cmn_free_1.dat | 4093640704 | 4294967296 | CLUSTER_NODE=4 |
| data_cmn_free_1.dat | 4093640704 | 4294967296 | CLUSTER_NODE=5 |
| data_cmn_free_1.dat | 4093640704 | 4294967296 | CLUSTER_NODE=6 |
+---------------------+------------+-------------+----------------+

Now I have to delete data from the table. After deletion, the table is empty but the tablespace remains - but in my understanding, the tablespace should be completely free again:

+---------------------+------------+-------------+----------------+
| FILE_NAME | FREE_SPACE | TOTAL_SPACE | EXTRA |
+---------------------+------------+-------------+----------------+
| data_cmn_free_1.dat | 4093640704 | 4294967296 | CLUSTER_NODE=4 |
| data_cmn_free_1.dat | 4093640704 | 4294967296 | CLUSTER_NODE=5 |
| data_cmn_free_1.dat | 4093640704 | 4294967296 | CLUSTER_NODE=6 |
+---------------------+------------+-------------+----------------+

When table is filled again, the tablespace is not used any more - the query above leads to the same output, FREE_SPACE = 4093640704, but should be 4294967296 again.

So I need to know how to use the tablespace again.