On Fri, May 14, 2021 at 11:48 AM Dilip Kumar <dilipbal...@gmail.com> wrote: > > On Fri, May 14, 2021 at 6:35 AM tsunakawa.ta...@fujitsu.com > <tsunakawa.ta...@fujitsu.com> wrote: > > > > From: Bharath Rupireddy <bharath.rupireddyforpostg...@gmail.com> > > > I think it will be useful to allow foreign tables to be VACUUMed if > > > the underlying FDW supports, currently VACUUM doesn't support foreign > > > tables, see [1]. > > > > Could you let us imagine more concretely how useful it will be? While > > TRUNCATE can be part of an application's data processing as alternative to > > DELETE, I think VACUUM is purely the data storage maintenance that's > > performed by the DBA and can be done naturally locally on the server where > > the table resides. (The existing ANALYZE on FDW is an exception; it's > > useful to also have data statistics locally.) > > I agree that TRUNCATE is a user-visible command so it is good to send > such a command to a remote server. But, sending ANALYZE and VACUUM to > FDW can have a similar use case. I mean based on the current data > changes/operation the DBA can decide whether it needs to generate the > statistic or whether it needs to do garbage collection. I think > ideally both these operations can be performed locally on the remote > server but if we are sending ANALYZE to the remote server then IMHO > there is some merit to sending VACUUM as well. Having said that, I > think the purpose of ANALYZE can be generic across the databases that > we want to update the statistic but VACUUM is different, it too much > depends upon how the data is stored (what MVCC mechanism they are > using) on the remote server and what is the vacuuming need for that > database. So maybe garbage collection should be controlled locally by > the DBA on that server.
Agree. Different MVCC databases can have different commands to clean up the bloat, their implementation of the vacuum's FdwRoutine can be implemented accordingly. postgres_fdw can prepare the "VACUUM rel;" command. Having said that, I don't think all the remote databases will have the same ANALYZE rel; or TRUNCATE rel; commands either. It's better left to the implementation of the FdwRoutine for a particular remote database. With Regards, Bharath Rupireddy. EnterpriseDB: http://www.enterprisedb.com
