On 09/12/2003 11:47 John Sidney-Woollett wrote:
Hi
I have a function called from a java app (via jdbc) which identifies images awaiting processing. This is determined by checking the WPImageStateID field on the WPImageHeader record (1=awaiting, 2=being processed, 3=complete).
The (jdbc) connection to the database is a standard one so I suspect that the transaction isolation level is Read uncommitted.
Unlikely as PostgreSQL doesn't support read uncommitted...
What I need is for the call to GetNextChangedImageHeader() to return the WDResourceID of the next WPImageHeader record awaiting processing.
The way it is written (I think that) it will either return the ID of a WPImageHeader record that genuinely is awaiting processing (if one is available), or will return -1 because it waited on a row lock which was released by another transaction on the same WPImageHeader record, but whose WPImageStateID is now no longer 1.
Does this look correct?
I think you need to play with a couple of psql sessions to sort this out. I think you might have a race condition here. --
Paul Thomas
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