Re: PostgreSQL intenal scheduler?

If I follow your use case, we have written something that just may fit your
scenario and plan to open source it rather soon.

It has several layers but let me boil it down. First we use an open sourced
auditing system to log changes to the source tables. This becomes your
queue. A postgres background worker will asynchronously process these
changes based on your configuration, which is highly configurable. It also
handles the concurrency you are questioning.

This allows you to build history tables without requiring you for example
to do it directly via a trigger. It also removes redundancy if you have the
same key updated multiple times. It assumes we are fine with the data built
not being 100% up to date data because these updates obviously don’t all
happen in the same transaction as the source data change.

Let me know if this interests you and I can share more.

Thanks,
Jeremy

On Wed, Sep 5, 2018 at 10:07 AM Thiemo Kellner <thiemo(at)gelassene-pferde(dot)biz>
wrote:

>
> Hi all
>
> I am designing a framework for historisation implementation (SCD). One
> feature I would like to provide is a table in that the actual state of
> an entity is put and if this is complete, this history table is
> "updated":
>
> ------------ -------------
> ==> | ENTITY_ACT | ==> | ENTITY_HIST |
> ------------ -------------
>
> I plan to use instead-of-triggers on the hist table that read the
> actual table and perfoms all necessary inserts und updates on the
> history table. If I want the termination of a record version (actually
> the record of a specific business key with a specific payload) to get
> propagated up and/or down referential integrities (no overlapping
> validities) I have to make sure that only one of those processes is
> modifying a table. I was thinking of a scheduler queue where the
> trigger would put a process request and PostgreSQL would work through.
> Is there a scheduler within PostgreSQL? I read the documentation and
> searched the web but could not find a hint. But before going another
> road or implementing something myself, I ask. Maybe this design is no
> good at all.
>
> Kind regards
>
> Thiemo
>
>
>