Lionel Bouton <lionel.bouton@xxxxxxx> writes: > Are txids in table file data indeed a means by which you can recover the > data written by a single transaction (assuming the txids don't overflow > the 32bit limit during the life of the cluster) ? They are. You could reduce the connections between different rows by writing them in different subtransactions of the parent transaction (use SAVEPOINT/RELEASE SAVEPOINT, or exception blocks in plpgsql). But unless there's many parallel transactions writing data, somebody could probably still reconstruct things by assuming that nearby XIDs represent subtransactions of a single transaction. > Are these t_xmin values ever cleaned up (by VACUUM or another mechanism) > ? If positive is there a way to configure the approximate time during > which these values can be recovered ? See VACUUM FREEZE. You couldn't hide connections immediately after insertion, but if the idea is to sanitize every so often, it'd help. > Is there a way to access these values by connecting to a PostgreSQL > server instead of analyzing in-memory or on-disk data ? SELECT xmin, ... FROM votes; regards, tom lane
