Re: Synchronizing slots from primary to standby

On Wed, Jan 31, 2024 at 9:20 PM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
>
> On Wed, Jan 31, 2024 at 7:42 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> >
> > On Wed, Jan 31, 2024 at 2:02 PM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> > >
> > > Thank you for updating the patches. As for the slotsync worker patch,
> > > is there any reason why 0001, 0002, and 0004 patches are still
> > > separated?
> > >
> >
> > No specific reason, it could be easier to review those parts.
>
> Okay, I think we can merge 0001 and 0002 at least as we don't need
> bgworker codes.
>

Agreed, and I am fine with merging 0001, 0002, and 0004 as suggested
by you though I have a few minor comments on 0002 and 0004. I was
thinking about what will be a logical way to split the slot sync
worker patch (combined result of 0001, 0002, and 0004), and one idea
occurred to me is that we can have the first patch as
synchronize_solts() API and the functionality required to implement
that API then the second patch would be a slot sync worker which uses
that API to synchronize slots and does all the required validations.
Any thoughts?

Few minor comments on 0002 and 0004
================================
1. The comments above HandleChildCrash() should mention about slot sync worker

2.
--- a/src/backend/storage/lmgr/proc.c
+++ b/src/backend/storage/lmgr/proc.c
@@ -42,6 +42,7 @@
#include "replication/slot.h"
#include "replication/syncrep.h"
#include "replication/walsender.h"
+#include "replication/logicalworker.h"

...
--- a/src/backend/utils/init/postinit.c
+++ b/src/backend/utils/init/postinit.c
@@ -43,6 +43,7 @@
#include "postmaster/autovacuum.h"
#include "postmaster/postmaster.h"
#include "replication/slot.h"
+#include "replication/logicalworker.h"

These new includes don't appear to be in alphabetical order.

3.
+ /* We can not have logical without replication */
+ if (!replication)
+ Assert(!logical);

I think we can cover both these conditions via Assert

--
With Regards,
Amit Kapila.