Re: Built-in plugin for logical decoding output

On 25/09/17 19:39, Petr Jelinek wrote:
>
> Well, test_decoding is not meant for production use anyway, no need for
> middleware to support it. The pgoutput is primarily used for internal
> replication purposes, which is why we need something with more
> interoperability in mind in the first place. The new plugin should still
> support publications etc though IMHO.
>
>>     However, having said that, and while json is a great output format
>> for interoperability, if there's a discussion on which plugin to include
>> next, I'd also favor one that has some more compact representation
>> format (or that supports several formats, not only json).
>>
> JSON is indeed great for interoperability, if you want more compact
> format, use either pgoutput or write something of your own or do
> conversion to something else in your consumer. I don't think postgres
> needs to provide 100 different formats out of the box when there is an
> API. The JSON output does not have to be extremely chatty either btw.
>

    In my opinion, logical decoding plugins that don't come with core
are close to worthless (don't get me wrong):

- They very unlikely will be installed in managed environments (an area
growing significantly).
- As anything that is not in core, raises concerns by users.
- Distribution and testing are non-trivial: many OS/archs combinations.

    Given the above, I believe having a general-purpose output plugin
in-core is critical to the use of logical decoding. As for 9.4-9.6 there
is test_decoding, and given that AWS uses it for production, that's kind
of fine. For 10 there is at least pgoutput, which could be used (even
though it was meant for replication). But if a new plugin is to be
developed for 11+, one really general purpose one, I'd say json is not a
good choice if it is the only output it would support. json is too
verbose, and replication, if anything, needs performance (it is both
network heavy and serialization/deserialization is quite expensive). Why
not, if one and only one plugin would be developed for 11+, general
purpose, do something that is, indeed, more general, i.e., that supports
high-performance scenarios too?

    Álvaro

--

Alvaro Hernandez

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