-- fails, binary plugin, textual consumer

SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'force-binary', '1');

ERROR: output plugincannot produce binary output

ERROR:logical decodingoutput plugin"test_decoding" produces binary output, but "pg_logical_slot_get_changes(name,pg_lsn,integer,text[])" expects textual data

-- succeeds, textual plugin, binary consumer

SELECT data FROM pg_logical_slot_get_binary_changes('regression_slot', NULL, NULL, 'force-binary', '0');

data

</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>

</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

ctx->options.output_type!=OUTPUT_PLUGIN_TEXTUAL_OUTPUT)

ereport(ERROR,

(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),

errmsg("output plugin cannot produce binary output")));

errmsg("logical decoding output plugin \"%s\" produces binary output, but \"%s\" expects textual data",

NameStr(MyReplicationSlot->data.plugin),

format_procedure(fcinfo->flinfo->fn_oid))));

ctx->output_writer_private=p;