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Improve documentation about binary/textual output mode for output plugins.

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Discussion: CAB7nPqQrqFzjqCjxu4GZzTrD9kpj6HMn9G5aOOMwt1WZ8NfqeA@mail.gmail.com,
    CAB7nPqQXc_+g95zWnqaa=mVQ4d3BVRs6T41frcEYi2ocUrR3+A@mail.gmail.com

Per discussion between Michael Paquier, Robert Haas and Andres Freund

Backpatch to 9.4 where logical decoding was introduced.
This commit is contained in:
Andres Freund
2014-10-01 13:13:59 +02:00
parent f78319fec8
commit ce84b0682c
3 changed files with 24 additions and 3 deletions
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21
doc/src/sgml/logicaldecoding.sgml
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@ -355,6 +355,24 @@ CREATE TABLE another_catalog_table(data text) WITH (user_catalog_table = true);
</para>
</sect2>
<sect2 id="logicaldecoding-output-mode">
<title>Output Modes</title>
<para>
Output plugin callbacks can pass data to the consumer in nearly arbitrary
formats. For some use cases, like viewing the changes via SQL, returning
data in a datatype that can contain arbitrary data (i.e. bytea) 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</>
to <literal>OUTPUT_PLUGIN_TEXTUAL_OUTPUT</> instead
of <literal>OUTPUT_PLUGIN_BINARY_OUTPUT</> in
the <link linkend="logicaldecoding-output-plugin-startup">startup
callback</>. In that case all the data has to be in the server's encoding
so a <type>text</> can contain it. This is checked in assertion enabled
builds.
</para>
</sect2>
<sect2 id="logicaldecoding-output-plugin-callbacks">
<title>Output Plugin Callbacks</title>
<para>
@ -405,7 +423,8 @@ typedef struct OutputPluginOptions
</programlisting>
<literal>output_type</literal> has to either be set to
<literal>OUTPUT_PLUGIN_TEXTUAL_OUTPUT</literal>
or <literal>OUTPUT_PLUGIN_BINARY_OUTPUT</literal>.
or <literal>OUTPUT_PLUGIN_BINARY_OUTPUT</literal>. See also
<xref linkend="logicaldecoding-output-mode"/>.
</para>
<para>
The startup callback should validate the options present in