Shaheed Haque <shaheedhaque@gmail.com> writes:
> How can there be a deadlock between updates to different rows (as per the
> bolded WHERE clauses)?
In isolation, there couldn't be ... but you've told us nothing of
what these transactions did beforehand. The simplest explanation
is that each one is already holding a lock on the row the other
one wants.
Maybe you are not committing between row updates?
If you have no better debugging ideas, try setting log_statements = all
and then examining everything the transactions did up to the failure.
regards, tom lane