You are right James.
So let's study my situation a bit closer instead of generically.
In my case a drop trigger statement is executing.
During this execution a new connection comes to the server.
Granted the other end of that connection belongs to the same jvm and
blocks the execution of drop trigger statement.
Question #1: Why is the connection not accepted?
This would mean that no new connections can be created while a drop
trigger statement is running which would sound bizarre.
Question #2: If the connection would be created why can't a delete
statement in another connection go through while drop trigger is blocking?
As drop trigger statement keeps waiting my cleanup statements would be
finished and thus let drop trigger finish also.
Personally I find threads to be sometimes magical.
I quess I am old fashioned in that way ;-)
- rami
On 29.5.2010 7:49, James Gregurich wrote:
threads are not magical. code has to be crafted to work correctly in concurrent mannger.
take a look at the H2 source code. it has mutexes in many places (search for the
"synchronized" keyword in the source). So if you have a thread that locks a
mutex then causes another thread to hit that same mutex, then deadlock is exactly what
you'll get.
On May 28, 2010, at 1:20 AM, Rami Ojares wrote:
Excuse me, but that sounds silly.
Threads have been invented!
One thread is the client, listening daemon opens a new server thread and so on.
Why do you think a very clever design is needed?
- rami
On 28.5.2010 9:54, James Gregurich wrote:
if you have the db engine connect to itself while processing a query, deadlock
is what I would expect to happen. It would take a very clever design to allow
the db engine to recursively call itself without deadlocking.
On May 27, 2010, at 1:58 AM, Rami Ojares wrote:
umm. are you asking the db engine to connect to itself from inside a trigger?
I am trying to do additional cleanup whenever a trigger is removed.
I can not cleanup if I don't have a connection to the database.
So yes.
- rami
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