There's no such field as OutputPluginOptions.output_mode;
it's actually output_type. Noted by T. Katsumata.
Discussion: https://postgr.es/m/
20170215072115.6101.29870@wrigleys.postgresql.org
data in a data type that can contain arbitrary data (e.g., <type>bytea</type>) is
cumbersome. If the output plugin only outputs textual data in the
server's encoding, it can declare that by
- setting <literal>OutputPluginOptions.output_mode</>
+ setting <literal>OutputPluginOptions.output_type</>
to <literal>OUTPUT_PLUGIN_TEXTUAL_OUTPUT</> instead
of <literal>OUTPUT_PLUGIN_BINARY_OUTPUT</> in
the <link linkend="logicaldecoding-output-plugin-startup">startup