Host telling me Query is running wild - processing 52 million records - assistance requested

My hoster is telling me that the query below is processing 52 million records every time it's run. Any ideas on where this query is, what it does or how to fix it would very much be appreciated. I have not changed anything in the installation in forever. The host thinks that the more content I write, somehow the query was pushed over the limit for warnings.

QUERY:
SELECT n.nid, n.type, n.status, n.promote, n.changed, u.dst FROM node n LEFT JOIN url_alias u ON u.src=CONCAT('node/',n.nid)

EXPLAIN:
explain SELECT n.nid, n.type, n.status, n.promote, n.changed, u.dst FROM node n LEFT JOIN url_alias u ON u.src=CONCAT('node/',n.nid)\G *************************** 1. row *************************** id: 1 select_type: SIMPLE table: n type: ALL possible_keys: NULL key: NULL key_len: NULL ref: NULL rows: 3971 Extra: *************************** 2. row *************************** id: 1 select_type: SIMPLE table: u type: ALL possible_keys: src key: NULL key_len: NULL ref: NULL rows: 15110 Extra: 2 rows in set (0.00 sec)

Other Info:
Time: 081028 16:01:51 # User@Host: root[root] @ [127.0.0.1] # Query_time: 53 Lock_time: 0 Rows_sent: 1644 Rows_examined: 22021902 use 351357_drupal5; SELECT n.nid, n.type, n.status, n.promote, n.changed, u.dst FROM node n LEFT JOIN url_alias u ON u.src=CONCAT('node/',n.nid);

Thanks in advance.