ceilometer resource table columns are not indexed

resource table has indexes only on internal_id and resource_id columns

mysql> show indexes from resource;
+----------+------------+-------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+----------+------------+-------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| resource | 0 | PRIMARY | 1 | internal_id | A | 2 | NULL | NULL | | BTREE | | |
| resource | 1 | ix_resource_resource_id | 1 | resource_id | A | 10 | NULL | NULL | YES | BTREE | | |
+----------+------------+-------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

user_id, project_id, source_id and metadata_hash columns are not indexed.

Its important to have all the columns indexed. metadata_hash is looked up at every insert, and others can be used by various queries using project_id, user_id, source_id as query parameters.

See related bugs on creating unique index on those columns https://bugs.launchpad.net/ceilometer/+bug/1419271 and https://bugs.launchpad.net/ceilometer/+bug/1353039. where unique indexes could not be created (due to large data size)

We should still index individual user_id, project_id, source_id and metadata_hash columns.