Re: Minimal logical decoding on standbys

Hi,

On 4/6/23 11:55 AM, Amit Kapila wrote:
> On Thu, Apr 6, 2023 at 12:10 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>>
>> On Wed, Apr 5, 2023 at 9:27 PM Drouvot, Bertrand
>> <bertranddrouvot(dot)pg(at)gmail(dot)com> wrote:
>>>
>>
>> Another comment on 0001.
>> extern void CheckSlotRequirements(void);
>> extern void CheckSlotPermissions(void);
>> +extern void ResolveRecoveryConflictWithLogicalSlots(Oid dboid,
>> TransactionId xid, char *reason);
>>
>> This doesn't seem to be called from anywhere.
>>
>
> Few other comments:
> ==================
> 0004
> 1.
> + * - physical walsenders in case of new time line and cascade
> + * replication is allowed.
> + * - logical walsenders in case of new time line or recovery is in progress
> + * (logical decoding on standby).
> + */
> + WalSndWakeup(switchedTLI && AllowCascadeReplication(),
> + switchedTLI || RecoveryInProgress());
>
> Do we need AllowCascadeReplication() check specifically for physical
> walsenders? I think this should be true for both physical and logical
> walsenders.
>

I don't think it could be possible to create logical walsenders on a standby if
AllowCascadeReplication() is not true, or am I missing something?

If so, I think it has to be set to true for the logical walsenders in all the case (like
done in V62 posted up-thread).

Andres, made the point up-thread that RecoveryInProgress() is always true, and
as we don't want to be woken up only when there is a time line change then I think
it has to be always true for logical walsenders.

> 0005
> 2.
> --- a/src/backend/access/transam/xlogfuncs.c
> +++ b/src/backend/access/transam/xlogfuncs.c
> @@ -38,6 +38,7 @@
> #include "utils/pg_lsn.h"
> #include "utils/timestamp.h"
> #include "utils/tuplestore.h"
> +#include "storage/standby.h"
>
> The header includes should be in alphabetical order.
>

Good catch, thanks! Done in V62.

Regards,

--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com