Help Required With SQL Subquery Across DB Link - Takes Long Time

Question

Hi,
Apologies if this is not the correct forum but I am implementing this through HTMLDB.
I am trying to run a SQL query over a DB link with a sub query on tables in my HTMLDB workspace.
The SQL query over the database link takes 1.23 seconds to run on it's own:
SELECT D.EMAIL_ADDRESS,
D.COL2,
D.COL3,
D.COL4,
D.COL5,
D.COL6,
T.COL1
FROM SCHEMA.TABLE1@DATABASELINK D,
SCHEMA.TABLE2@DATABASELINK T
WHERE D.TABLE_JOIN = T.TABLE_JOIN
AND T.COL1 = '1111111'
AND UPPER(D.COL2) IN ('XXXXXX','YYYYYY')
The SQL query based on HTMLDB workspace tables takes 0.01 seconds to run on it's own:
SELECT UPPER(A.EMAIL_ADDRESS)
FROM HTMLDBTABLE1 M, HTMLDBTABLE2 A
WHERE M.TABLE_JOIN = A.TABLE_JOIN
AND M.ID = 222
However when I try and run these together the results take 280 seconds to complete:
SELECT D.EMAIL_ADDRESS,
D.COL2,
D.COL3,
D.COL4,
D.COL5,
D.COL6,
T.COL1
FROM SCHEMA.TABLE1@DATABASELINK D,
SCHEMA.TABLE2@DATABASELINK T
WHERE D.TABLE_JOIN = T.TABLE_JOIN
AND T.COL1 = '1111111'
AND UPPER(D.COL2) IN ('XXXXXX','YYYYYY')
AND NOT EXISTS
(SELECT UPPER(A.EMAIL_ADDRESS)
FROM HTMLDBTABLE1 M, HTMLDBTABLE2 A
WHERE M.TABLE_JOIN = A.TABLE_JOIN
AND UPPER(A.EMAIL_ADDRESS) = UPPER(D.EMAIL_ADDRESS)
AND M.ID = 222)
Does anyone have any idea why this query is taking so long?
Please let me know if you require additional information.
Many thanks,
Richard.

Answer 1

I've updated my profile to show my email address, so go ahead and email me the strace output (compressed please). Maximum attachment size for emails to Oracle is 10MB (encoded), so split the strace output in 5MB chunks if necessary.
poll() is not normally used by the Oracle network layer for client-server connections. So this may be related to an OS network service, such as DNS or NIS. The strace should make this clear (to me anyway).
Edited by: herb on Aug 14, 2009 10:25 AM