Op 24 feb 2011, om 20:49 heeft [email protected] het volgende
geschreven:
What is the expected behaviour of sequence numbers under pg
concurrence model?
From the manual:
Important: To avoid blocking concurrent transactions that obtain
numbers from the same sequence, a nextval operation is never rolled
back; that is, once a value has been fetched it is considered used,
even if the transaction that did the nextval later aborts. This means
that aborted transactions might leave unused "holes" in the sequence
of assigned values. setval operations are never rolled back, either.
http://www.postgresql.org/docs/current/static/functions-sequence.html
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?
Frank Heikens
