Re: [Proposal] Fully WAL logged CREATE DATABASE - No Checkpoints

On Sat, Mar 26, 2022 at 5:55 PM Dilip Kumar <dilipbalaut@gmail.com> wrote:
>
> On Fri, Mar 25, 2022 at 8:16 PM Dilip Kumar <dilipbalaut@gmail.com> wrote:
> >
> > > On a quick look, I'm guessing that XLOG_DBASE_CREATE_WAL_LOG will need
> > > to mirror some of the logic that was added to the replay code for the
> > > existing strategy, but I haven't figured out the details.
> > >
> >
> > Yeah, I think I got it, for XLOG_DBASE_CREATE_WAL_LOG now we will have
> > to handle the missing parent directory case, like Alvaro handled for
> > the XLOG_DBASE_CREATE(_FILE_COPY) case.
>
> I have updated the patch so now we skip the XLOG_DBASE_CREATE_WAL_LOG
> as well if the tablespace directory is missing.  But with our new
> wal_log method there will be other follow up wal logs like,
> XLOG_RELMAP_UPDATE, XLOG_SMGR_CREATE and XLOG_FPI.
>
> I have put the similar logic for relmap_update WAL replay as well,

There was some mistake in the last patch, basically, for relmap update
also I have checked the missing tablespace directory but I should have
checked the missing database directory so I have fixed that.

> Now, is it possible to get the FPI without smgr_create wal in other
> cases?  If it is then that problem is orthogonal to this path, but
> anyway I could not find any such scenario.

I have digged further into it, tried manually removing the directory
before XLOG_FPI, but I noticed that during FPI also
XLogReadBufferExtended() take cares of creating the missing files
using smgrcreate() and that intern take care of missing directory
creation so I don't think we have any problem here.

-- 
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com