Re: Logical Replication and Character encoding

On 14/02/17 03:23, Kyotaro HORIGUCHI wrote:
> At Sat, 4 Feb 2017 21:27:32 +0100, Petr Jelinek <petr(dot)jelinek(at)2ndquadrant(dot)com> wrote in <bcc7f7e9-f558-b19e-b544-000ba7cf286c(at)2ndquadrant(dot)com>
>> Hmm I wonder if we should just make the subscriber send the
>> client_encoding always (based on server encoding of the subscriber).
>> That should solve the issue in combination with your patch no?
>
> Yeah, right. I considered that a subscriber might want to set its
> own value for that but that is useless.
>
> The attached patch does the following things to just prevent
> making a logical replication connection between databases with
> inconsistent encodings.
>
> - added client_encoding with subscriber(or standby)'s encoding at
> the last of options in libpqrcv_connect.
>
> - CheckLogicalDecodingRequirements refuses connection for a
> request with inconsistent encodings.
>
>> ERROR: logical replication requires consistent encodings on both side (publisher = UTF8, subscriber = EUC_JP)
>

I am not quite convinced that this should be handled by logical decoding
itself. It's quite possible to have output plugins that will handle this
correctly for their use-cases (by doing similar conversion you did in
the original patch) so they should not be prevented doing so.
So it's probably better to check this in the plugin.

I do like the idea of just using client_encoding in libpqrcv_connect though.

--
Petr Jelinek http://www.2ndQuadrant.com/
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