Re: Logical walsenders don't process XLOG_CHECKPOINT_SHUTDOWN

Hi,

On 2023-07-25 14:31:00 +0530, Amit Kapila wrote:
> To ensure that all the data has been sent during the upgrade, we can
> ensure that each logical slot's confirmed_flush_lsn (position in the
> WAL till which subscriber has confirmed that it has applied the WAL)
> is the same as current_wal_insert_lsn. Now, because we don't send
> XLOG_CHECKPOINT_SHUTDOWN even on clean shutdown, confirmed_flush_lsn
> will never be the same as current_wal_insert_lsn. The one idea being
> discussed in patch [1] (see 0003) is to ensure that each slot's LSN is
> exactly XLOG_CHECKPOINT_SHUTDOWN ago which probably has some drawbacks
> like what if we tomorrow add some other WAL in the shutdown checkpoint
> path or the size of record changes then we would need to modify the
> corresponding code in upgrade.

Yea, that doesn't seem like a good path. But there is a variant that seems
better: We could just scan the end of the WAL for records that should have
been streamed out?

Greetings,

Andres Freund