Re: Theory question

On Thu, Nov 14, 2013 at 7:58 AM, Jayadevan <maymala(dot)jayadevan(at)gmail(dot)com>wrote:

> Jeff Janes wrote
> > No. The checkpointer writes all data that was dirty as of a certain time
> > (the start of the checkpoint) regardless of how often it was used since
> > dirtied, and the background writer writes data that hasn't been used
> > recently, regardless of when it was first dirtied. Neither knows or
> cares
> > whether the data being written was committed, rolled back, or still in
> > progress.
>
> Thank you. So checkpointer writes "all dirty data" while backgrounder
> writes
> "all or some dirty data" depending on some (Clocksweep?) algorithm.
> Correct?
> From this discussion
>
> http://postgresql.1045698.n5.nabble.com/Separating-bgwriter-and-checkpointer-td4808791.html
> <
> http://postgresql.1045698.n5.nabble.com/Separating-bgwriter-and-checkpointer-td4808791.html
> >
> the bgwrites has some 'other dutties'. Probably those involve marking the
> buffers - when they were last used, how frequently etc?
>
>
>
> That should have been "backgrounder writes "all or some dirty or non-dirty
data" "...