What is the expected behaviour of sequence numbers under pg concurrence model?
E.g. Uncommitted transaction 1 in progress has inserted 5 tuples into table
foo. Meanwhile uncommitted transaction 2 in progress inserts 100 tuples into
table foo. If the sequence number for the pk started at 1000 before these
transactions, what are the sequence numbers for transaction 1, 2, and the final
sequence number if they both commit? One rollback's? Both rollback? One hangs
open while the other commits? One hang and one rollback's?
