"Tom Lane" <[EMAIL PROTECTED]> writes: > Simon Riggs <[EMAIL PROTECTED]> writes: >> I propose creating "Visibility Groups" that *explicitly* limit the >> ability of a transaction to access data outside its visibility group(s). >> By default, visibility_groups would be NULL, implying potential access >> to all tables. > > I think this would be a lot of mechanism and complication that will go > completely unused in the field. It'll be impossible even to explain let > alone to use effectively, for anyone who's not intensely steeped in the > details of MVCC.
I think Simon's interface was overly complex but if we can simplify it then it could be useful. As Grittner mentioned implicit queries could make use of it automatically. Also pg_dump or Slony could make use of it automatically. And while Alvaro is absolutely right that we should take care of the inaccessible records between an old long-running transaction and more recently started transactions that doesn't really completely solve the problem. If you have a large table consisting of old records which are gradually being replaced with newer records a long-running transaction will prevent any of those old records from being vacuumed. -- Gregory Stark EnterpriseDB http://www.enterprisedb.com Ask me about EnterpriseDB's On-Demand Production Tuning -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
