Re: Proposal: Generic WAL logical messages

On 1 January 2016 at 03:59, Petr Jelinek <petr(at)2ndquadrant(dot)com> wrote:

> I would like to introduce concept of generic WAL logical messages.
>

Couple of points...

* Genenric misspelled

* You call them "logical messages" here, but standby messages in code. But
they only apply to logical decoding, so "logical message" seems a better
name. Can we avoid calling them "messages" cos that will get confusing.

> For standard WAL reply, these are basically noop
>

We should document that.

> These messages can be both transactional (decoded on commit) or
> non-transactional (decoded immediately). Each message has prefix to
> differentiate between individual plugins. The prefix has to be registered
> exactly once (in similar manner as security label providers) to avoid
> conflicts between plugins.
>

I'm not sure what "transactional" means, nor is that documented.
(Conversely, I think "immediate" fairly clear)

Are they fired only on commit? (Guess so)
Are they fired in the original order, if multiple messages in same
transaction? (Hope so)
Are they fired as they come in the original message sequence, or before
anything else or after everything else? For example, cache invalidation
messages are normally fired right at the end of a transaction, no matter
when they were triggered.

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