Hi Justin, that came to my mind also. Then I tried and found that not always a new WAL is created. I admit I tried on a test DC with no other transactions going on. Maybe I should have done that. Anyway, I also always do the checkpoint first and then the WAL switch, which in my case is also an old habit from Oracle. ;-) Cheers, Paul > On 11. Mar, 2020, at 16:51, Justin <zzzzz.graf@xxxxxxxxx> wrote: > > Question everyone isn't this a problem with the order of operations? > > switching the wal files then running checkpoint means the Checkpoint can cross wal files, so the previous wal file can not be deleted??? > > To my understanding the order operations should be > > Checkpoint > which flushes everything to disk, then > pg_switch_wal() > > which creates an empty wal file and the previous wal can be deleted? > > http://www.interdb.jp/pg/pgsql09.html#_9.7. > https://www.postgresql.org/docs/current/wal-configuration.html > > Or am i missing something? > > On Wed, Mar 11, 2020 at 11:45 AM Simon Riggs <simon@xxxxxxxxxxxxxxx> wrote: > On Wed, 11 Mar 2020 at 08:59, Torsten Krah <krah.tm@xxxxxxxxx> wrote: > Hi, > > I am building a docker image with a postgresql 12.2 instance and while > doing so and importing a dump and running some update scripts wal size > is increasing. > > When finished I don't need all those wal files anymore and tried to > force the daemon to clean them up and tried this: > > select pg_switch_wal(); > CHECKPOINT; > > and did wait for a minute. > > Sometimes it works and wal files are cleaned and moved away so my image > size is way smaller - but it does not happen always in that minute. > > So is there a way to tell postgres to force the housekeeping of the wal > stuff via a statement / command line tool? > In a "normal" running instance it just takes care of itself and it will > happen sooner or later and it doesn't really matter when that will > happen - but with my docker image which is automatically build it would > be nice to have a deterministic way of trigger that to reduce the final > size image. > > The size of the task varies, so sometimes takes longer than 60s, depending upon your hardware. > > -- > Simon Riggs http://www.2ndQuadrant.com/ > PostgreSQL Solutions for the Enterprise
