RE: [PoC] pg_upgrade: allow to upgrade publisher node

Dear Peter,

Thank you for reviewing!

> 1. check_and_dump_old_cluster
> 
> CURRENT CODE (with v26-0003 patch applied)
> 
> /* Extract a list of logical replication slots */
> get_old_cluster_logical_slot_infos();
> 
> ...
> 
> /*
> * Logical replication slots can be migrated since PG17. See comments atop
> * get_old_cluster_logical_slot_infos().
> */
> if (GET_MAJOR_VERSION(old_cluster.major_version) >= 1700)
> {
> check_old_cluster_for_lost_slots();
> 
> /*
> * Do additional checks if a live check is not required. This requires
> * that confirmed_flush_lsn of all the slots is the same as the latest
> * checkpoint location, but it would be satisfied only when the server
> * has been shut down.
> */
> if (!live_check)
> check_old_cluster_for_confirmed_flush_lsn();
> }
> 
> 
> SUGGESTION
> 
> /*
>  * Logical replication slots can be migrated since PG17. See comments atop
>  * get_old_cluster_logical_slot_infos().
>  */
> if (GET_MAJOR_VERSION(old_cluster.major_version) >= 1700) // NOTE 1a.
> {
>   /* Extract a list of logical replication slots */
>   get_old_cluster_logical_slot_infos();
> 
>   if (count_old_cluster_slots()) // NOTE 1b.
>   {
>     check_old_cluster_for_lost_slots();
> 
>     /*
>      * Do additional checks if a live check is not required. This requires
>      * that confirmed_flush_lsn of all the slots is the same as the latest
>      * checkpoint location, but it would be satisfied only when the server
>      * has been shut down.
>      */
>     if (!live_check)
>       check_old_cluster_for_confirmed_flush_lsn();
>   }
> }
> 
> ~~
> 
> Benefits:
> 
> 1a.
> One version check instead of multiple.
> 
> ~
> 
> 1b.
> Upfront slot counting means
> - only call 1 time to count_old_cluster_slots().
> - unnecessary calls to other check* functions are avoided
> 
> ~
> 
> 1c.
> get_old_cluster_logical_slot_infos
> - No version check is needed.
> 
> check_old_cluster_for_lost_slots
> - Call to count_old_cluster_slots is not needed
> - Quick exit not needed.
> 
> check_old_cluster_for_confirmed_flush_lsn
> - Call to count_old_cluster_slots is not needed
> - Quick exit not needed.
> 
> ~~~
> 
> 2. check_old_cluster_for_lost_slots
> 
> + /* Quick exit if the cluster does not have logical slots. */
> + if (count_old_cluster_logical_slots() == 0)
> + return;
> 
> Refer [1]#4. Can remove this because #1b above.
>
> 3. check_old_cluster_for_confirmed_flush_lsn
> 
> + /* Quick exit if the cluster does not have logical slots. */
> + if (count_old_cluster_logical_slots() == 0)
> + return;
> 
> Refer [1]#5. Can remove this because #1b above.

IIUC these points were disagreed by Amit, so I would keep my code until he posts
opinions.

> 4. .../t/003_logical_replication_slots.pl
> 
> /shipped/replicated/
> 
> Kuroda-san 26/8 wrote:
> You meant to say s/replicated/shipped/, right? Fixed.
> 
> No, I meant what I wrote for [1]#7. I was referring to the word
> "shipped" in the message 'check changes are shipped to the
> subscriber'. Now there are 2 places to change instead of one.
>

Oh, sorry for that. Both places was fixed.

Best Regards,
Hayato Kuroda
FUJITSU LIMITED