Re: A Modest Upgrade Proposal
| От | Craig Ringer |
|---|---|
| Тема | Re: A Modest Upgrade Proposal |
| Дата | |
| Msg-id | CAMsr+YFz63drDzjTwmTWSzvop7V+axrK1Ncq56aSNhqbULJmow@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: A Modest Upgrade Proposal (Bruce Momjian <bruce@momjian.us>) |
| Ответы |
Re: A Modest Upgrade Proposal
Re: A Modest Upgrade Proposal |
| Список | pgsql-hackers |
On 28 July 2016 at 04:35, Bruce Momjian <bruce@momjian.us> wrote:
On Fri, Jul 8, 2016 at 12:18:28AM +0100, Simon Riggs wrote:
> On 7 July 2016 at 21:10, Robert Haas <robertmhaas@gmail.com> wrote:
>
> pg_upgrade does that, kinda. I'd like to have something better, but
> in the absence of that, I think it's quite wrong to think about
> deprecating it, even if we had logical replication fully integrated
> into core today. Which we by no means do.
>
> I don't see any problem with extending pg_upgrade to use logical replication
> features under the covers.
>
> It seems very smooth to be able to just say
>
> pg_upgrade --online
>
> and then specify whatever other parameters that requires.
>
> It would be much easier to separate out that as a use-case so we can be sure we
> get that in 10.0, even if nothing else lands.
Uh, while "pg_upgrade --online" looks cool, I am not sure a solution
based on logical replication would share _any_ code with the existing
pg_upgrade tool, so it seems best to use another binary for this.
It might, actually. One approach for online upgrade is to:
* pg_basebackup the master
* start the replica and let it catch up
* create a logical replication slot on the master
* replace the replication.conf on the basebackup so it stops recovery at the lsn of the replication slot's confirmed_flush_lsn
* stop the replica and pg_upgrade it
* have the upgraded replica, now a master, replay from the old master over logical replication
* once caught up, switch over
This means a full dump and reload with a full rebuild of all indexes, etc, isn't needed. All shared catalog stuff is copied (until we switch to logical rep for the final catch-up).
I guess we could use the pg_dump/pg_restore pg_upgrade code to create
the objects, and use logical replication to copy the rows, but what does
this gain us that pg_dump/pg_restore doesn't?
A consistent switch-over point, where the upgrade can happen while the master is still writing.
We create a slot, dump from the slot's exported snapshot, and switch over to logical replication consistently at the end of the dump.
That's pretty much what BDR and pglogical do.
В списке pgsql-hackers по дате отправления: