Re: Incremental backup

On 10/28/21 2:06 PM, Adrian Klaver wrote:
> On 10/28/21 11:48, Ron wrote:
>> On 10/28/21 1:00 PM, Adrian Klaver wrote:
>>> On 10/28/21 10:51, Ron wrote:
>>>
>
>> Not doable in Postgresql because WAL files are global to cluster. I've
>> read multiple times that will not be changed.
>
> Yet somehow logical replication does it:
>
> https://www.postgresql.org/docs/14/logical-replication-architecture.html
>
> "
> Logical replication is built with an architecture similar to physical
> streaming replication (see Section 27.2.5). It is implemented by
> “walsender” and “apply” processes. The walsender process starts logical
> decoding (described in Chapter 49) of the WAL and loads the

Scans the (global) WAL data for only the that portion from the relevant
database?

If so, definitely not the same as having per-database WAL files.

Just as importantly, replication is not, and never will be, a substitute for
backups.

> standard logical decoding plugin (pgoutput). The plugin transforms the
> changes read from WAL to the logical replication protocol (see Section
> 53.5) and filters the data according to the publication specification. The
> data is then continuously transferred using the streaming replication
> protocol to the apply worker, which maps the data to local tables and
> applies the individual changes as they are received, in correct
> transactional order.
> "
>
> https://www.postgresql.org/docs/14/logical-replication.html
>
> "The typical use-cases for logical replication are:
>
>     Sending incremental changes in a single database or a subset of a
> database to subscribers as they occur.
>  ...
> "

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