Re: Improve pg_sync_replication_slots() to wait for primary to advance

On Wed, Dec 17, 2025 at 3:58 PM Zhijie Hou (Fujitsu)
<houzj(dot)fnst(at)fujitsu(dot)com> wrote:
>
> Here is a small patch to fix it.
>

Thanks, I've pushed the patch. BTW, looking at the code of slot_sync
API code path, I could think of the following improvements.

*
if (remote_slot->confirmed_lsn > latestFlushPtr)
{
update_slotsync_skip_stats(SS_SKIP_WAL_NOT_FLUSHED);

/*
* Can get here only if GUC 'synchronized_standby_slots' on the
* primary server was not configured correctly.
*/
ereport(AmLogicalSlotSyncWorkerProcess() ? LOG : ERROR,
errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),

Can we change this ERROR to LOG even for API as now the API also
retires to sync the slots during initial sync?

* The use of the slot_persistence_pending flag in the internal APIs
seems to be the reverse of what it should be. I mean to say that
initially it should be true and when we actually persist the slot then
we can set it to false.

* We can retry to sync all the slots present in the primary at the
start of API, not only temporary slots. If we do this then the
previous point may not be required. Also, please mention something
like: "It retries cyclically until all the failover slots that existed
on primary at the start of the function call are synchronized." in the
function description [1] as well.

[1] - https://www.postgresql.org/docs/devel/functions-admin.html#FUNCTIONS-REPLICATION
--
With Regards,
Amit Kapila.