Re: Oracle vs. PostgreSQL - a comment

On Wed, Jun 3, 2020 at 7:45 PM Andreas Joseph Krogh <andreas(at)visena(dot)com>
wrote:

> På onsdag 03. juni 2020 kl. 18:50:12, skrev Jeremy Schneider <
> schnjere(at)amazon(dot)com>:
>
> > On 6/2/20 1:30 PM, Stephen Frost wrote:
> >> No, nothing does as PG doesn't support it as we have one WAL stream for
> >> the entire cluster.
>
> On 6/2/20 11:38, Ron wrote:
> > Right. Making WAL files specific to a database should be high on the
> > list of priorities.
>
> Did Oracle change this? Last time I looked, I don't think Oracle
> supported local redo in their multitenant architecture either.
>
>
>
> Regardless of what Oracle does, I agree this would be a huge step in the
> right direction for pg-DBAs.
> I have absolutely no clue about how much work is required etc., but I
> think it's kind of strange that no companies have invested in making this
> happen.
>

I manage database clusters where the number of databases is a reason not to
do logical replication based upgrades, where pg_upgrade is far preferred
instead.

If this were to be the case, I would be very concerned that a bunch of
things would have to change:
1. Shared catalogs would have txid problems unless you stay with global
txids and then how do local wal streams work there?
2. Possibility that suddenly streaming replication has the possibility of
different databases having different amounts of lag
3. Problems with io management on WAL on high throughput systems (I have
systems where a db cluster generates 10-20TB of WAL per day)

So I am not at all sure this would be a step in the right direction or
worth the work.

>
> --
> Andreas Joseph Krogh
>

--
Best Wishes,
Chris Travers

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