I am running MySQL 5.5.9 x86_64 RPM as downloaded from mysql.com. Running on CentOS 5.5 Xen DomU.

I have enabled the Query_cache however MySQL NEVER uses it. All of my tables are InnoDB. Why is the Qcache never hit?

Here are my settings.

mysql> SELECT VERSION();
+-----------+
| VERSION() |
+-----------+
| 5.5.9     |
+-----------+
1 row in set (0.00 sec)

mysql> SHOW VARIABLES LIKE '%query_cache%';
+------------------------------+-----------+
| Variable_name                | Value     |
+------------------------------+-----------+
| have_query_cache             | YES       |
| query_cache_limit            | 2097152   |
| query_cache_min_res_unit     | 4096      |
| query_cache_size             | 536870912 |
| query_cache_type             | ON        |
| query_cache_wlock_invalidate | OFF       |
+------------------------------+-----------+
6 rows in set (0.00 sec)

mysql> show status like 'Qcache%';
+-------------------------+-----------+
| Variable_name           | Value     |
+-------------------------+-----------+
| Qcache_free_blocks      | 1         |
| Qcache_free_memory      | 536852824 |
| Qcache_hits             | 0         |
| Qcache_inserts          | 0         |
| Qcache_lowmem_prunes    | 0         |
| Qcache_not_cached       | 7665775   |
| Qcache_queries_in_cache | 0         |
| Qcache_total_blocks     | 1         |
+-------------------------+-----------+
8 rows in set (0.00 sec)