On Sat, Jan 23, 2016 at 1:16 PM, Jinhua Luo <luajit.io@gmail.com> wrote: > > Hi, > > The vacuum doesn't recycle the rows obsoleted by update?
>
It does free up the space which can be used by future inserts.
> I don't think > so. In the above vacuum result, I do not delete any rows, but the > vacuum still recycles a fraction of rows, obviously they're obsoleted > by update. > > I know plain vacuum (without full option) do not reduce the size of > the whole table file/segments, but it should refresh the fsm. In my > case, the update statement did modify the index column, but is it > related to the fsm? I think anyways, the update would obsolete > previous versions, as long as they are not hold by any active > transactions, they would be recycled and count in the fsm, right?
I also think it will be added to fsm.
> I > just cannot understand why the recycle ratio is not 50%. >
At the moment, I am also not able to see why it is so. You might
want to first try with a simple test (Can you extract insert/update
statements from application and run it manually for couple of times
and then run Vacuum to see the result).
By anychance have you set a value for vacuum_defer_cleanup_age?
