Re: Handing off SLRU fsyncs to the checkpointer

On Mon, Sep 21, 2020 at 2:19 PM Thomas Munro <thomas.munro@gmail.com> wrote:
> While scanning for comments and identifier names that needed updating,
> I realised that this patch changed the behaviour of the ShutdownXXX()
> functions, since they currently flush the SLRUs but are not followed
> by a checkpoint.  I'm not entirely sure I understand the logic of
> that, but it wasn't my intention to change it.  So here's a version
> that converts the existing fsync_fname() to fsync_fname_recurse() to

Bleugh, that was probably a bad idea, it's too expensive.  But it
forces me to ask the question: *why* do we need to call
Shutdown{CLOG,CommitTS,SUBTRANS, MultiXact}() after a creating a
shutdown checkpoint?  I wondered if this might date from before the
WAL, but I see that the pattern was introduced when the CLOG was moved
out of shared buffers into a proto-SLRU in ancient commit 2589735da08,
but even in that commit the preceding CreateCheckPoint() call included
a call to CheckPointCLOG().