Hi Pavel:
Will you be able to find the exact query executing from AquaDataStudio to
Derby? Will the query be in derby.log? If you have the query, do you mind
executing the query in ij? Also, when the query hang, would you mind getting
the
thread dump? You can edit out the proprietary parts
I am just thinking out loud here. I did another query for the same table
as
T1. It still work with my simple table.
i.e.
==
ij> select T.col1, T.col2 from T1 T, (select col1, col2 from T1 as T2) as M wher
e M.col1 = T.col1;
COL1 |COL2
--------------------------------
1 |row 1
2 |row 2
Hope this help,
Lily
________________________________
From: Pavel Bortnovskiy <[email protected]>
To: Lily Wei <[email protected]>
Cc: Derby Discussion <[email protected]>
Sent: Thu, January 20, 2011 2:43:11 PM
Subject: Re: Can it be that Derby (in-memory) is deadlocking on this query?
(UPDATE)
Hello, Lily:
thank you for your response.
while I am still trying to create a test for Derby users, your experiment is
not
the same. Notice that in our query we are joining on the same table. So, T2 is
not a different table. It's still the same T1 table, but aliased as T2...
try something like this:
select
*
from
TABLE T1,
(
select
T2.col
from
TABLE T2
) as M
where
M.col = T1.col
Once I succeed reproducing the error, I will show my test.
What makes me suspect that there is a problem with Derby is two-fold:
- our code seems to hang in ResultSet.next(), which is a call to Derby JDBCAPI
implementation
- accessing those in-memory tables with AquaDataStudio and running the same
query never returns/succeeds (I stopped after 20 minutes of having it running,
where as the subqueries themselves run in a few milliseconds). AquaDataStudio
is
a commercial product and I doubt that it breaks precisely at the same point and
query as our code...
P.
