This patch adds the ability to retrieve async notifications using dblink, via the addition of the function dblink_get_notify.
It is written against cvs head, includes documentation and regression testing. It compiles, tests and works well.
I would be interested in some feedback on the regression test. My initial thought was to test the function as thoroughly as possible. So I perform listen and notify commands within the test to be able to test all aspects of the code. Even though this works well for me, I get the feeling that this is not the correct way to do it. I can find no other testing of the listen/notify functionality in the regression tests, and I imagine this is for good reason. If someone would care to explain this, and maybe give a hint about what amount of testing is appropriate for this fairly trivial patch, it would be appreciated.
