Robert Haas wrote: > On Fri, Apr 24, 2015 at 3:04 PM, Alvaro Herrera > <alvhe...@2ndquadrant.com> wrote:
> > I think what we need here is something that does heap_update to tuples > > at the end of the table, moving them to earlier pages; then wait for old > > snapshots to die (the infrastructure for which we have now, thanks to > > CREATE INDEX CONCURRENTLY); then truncate the empty pages. Of course, > > there are lots of details to resolve. It doesn't really matter that > > this runs for long: a process doing this for hours might be better than > > AccessExclusiveLock on the table for a much shorter period. > > Why do you need to do anything other than update the tuples and let > autovacuum clean up the mess? Sure, that's one option. I think autovac's current approach is too heavyweight: it always has to scan the whole relation and all the indexes. It might be more convenient to do something more fine-grained; for instance, maybe instead of scanning the whole relation, start from the end of the relation walking backwards and stop once the first page containing a live or recently-dead tuple is found. Perhaps, while scanning the indexes you know that all CTIDs with pages higher than some threshold value are gone; you can remove them without scanning the heap at all perhaps. -- Álvaro Herrera http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
