Part of the md_docs_topics_usagetracking system on a Client.

Fields:

eu_row_id - auto-increment row ID for internal use. Primary key.
eu_entity_id - Serialized entity ID for the entity that has usage
eu_aspect - Which aspect of the entity is being used. (See md_docs_topics_usagetracking)
eu_page_id - the ID of the page using the entity; refers to page.page_id.

+--------------+----------------+------+-----+---------+----------------+
| Field        | Type           | Null | Key | Default | Extra          |
+--------------+----------------+------+-----+---------+----------------+
| eu_row_id    | bigint(20)     | NO   | PRI | NULL    | auto_increment |
| eu_entity_id | varbinary(255) | NO   | MUL | NULL    |                |
| eu_aspect    | varbinary(37)  | NO   |     | NULL    |                |
| eu_page_id   | int(11)        | NO   | MUL | NULL    |                |
+--------------+----------------+------+-----+---------+----------------+

Implied relations:

Extra Indexes:

UNIQUE eu_entity_id , eu_aspect, eu_page_id - record one usage per page per aspect of an entity
eu_page_id, eu_entity_id - look up (and especially, delete) usage entries by page id

Example data:

eu_row_id	eu_entity_id	eu_aspect	eu_page_id
158829644	Q99	O	73443972
88145275	L10102	L	56193021
157778764	L10151-S1	L	53636569
91511974	Q645	D.en	3334
96856295	P455	L.en	3334
39020318	Q6339058	C.P625	13831293