Hi,
I'm seeing a strage behaviour which I seem to cannot get a hold of. I have the
problem that sometimes when I do a select on a table, that table is reported as
being empty (empty result set) although it definitely contains data.
What I'm doing is I'm starting a Derby network server within one program,
doing some selects, inserts, etc. in that program and it works perfectly.
I then try to access the same database from another Java program. And here it
depends.
If I use a debugger and set a breakpoint in the server program during startup,
right after the database has been created and the program obtained a connection
to it, then the client program will work (can do selects without problems and
getting data from the tables).
I disconnect the client program and let the server program continue (removing
the breakpoint in the debugger). The server program will internally do some
selects, updates, etc.
If I later reconnect the same, previously working client and try to do a
select on the same table as previously, that table is reported as completely
empty (empty result set although it definitely contains some data). To verify,
if I reattach the debugger to the server program and execute the same select
with server program's connection to the database the very same table is full of
data.
What could be the cause of this? Is this a setup or locking issue?
Best Regards
Ralph
PS: I also tried a more complex setup again setting a breakpoint in the
server program right after it has creates the DB and connected to it. I then
start the first client. The first client can successfully see data in the
table. I let the server progrm continue (which will do some selects, updates,
etc.). The first client can still see all data. I then connect a second client
(with the first one still connected) and try to do a select: table is emtpy.
Doing the very same select in the first client program will return data just
fine. Looks like the time the client connection to the Derby database is made
determines whether the client can see data in some tables or it cannot.
Interestingly system tables will always return data in all clients no matter
when they connected.
