[support] Issue with a Query that's running wild

[Allen Stern]

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 at 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.