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doc: Enhance documentation for postgres_fdw_get_connections() output columns. 

The documentation previously described the output columns of
postgres_fdw_get_connections() in text format, which was manageable
for the original two columns. However, upcoming patches will add
new columns, making text descriptions less readable.

This commit updates the documentation to use a table format,
making it easier for users to understand each output column.

Author: Fujii Masao, Hayato Kuroda
Reviewed-by: Hayato Kuroda
Discussion: https://postgr.es/m/d04aae8d-05f5-42f4-a263-b962334d9f75@oss.nttdata.com
This commit is contained in:
Fujii Masao 2024-07-26 20:47:05 +09:00
parent 274bbced85
commit 284c030a10
1 changed files with 42 additions and 11 deletions
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53
doc/src/sgml/postgres-fdw.sgml
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@ -780,17 +780,9 @@ OPTIONS (ADD password_required 'false');
<term><function>postgres_fdw_get_connections(OUT server_name text, OUT valid boolean) returns setof record</function></term>
<listitem>
<para>
This function returns the foreign server names of all the open
connections that <filename>postgres_fdw</filename> established from
the local session to the foreign servers. It also returns whether
each connection is valid or not. <literal>false</literal> is returned
if the foreign server connection is used in the current local
transaction but its foreign server or user mapping is changed or
dropped (Note that server name of an invalid connection will be
<literal>NULL</literal> if the server is dropped),
and then such invalid connection will be closed at
the end of that transaction. <literal>true</literal> is returned
otherwise. If there are no open connections, no record is returned.
This function returns information about all open connections postgres_fdw
has established from the local session to foreign servers. If there are
no open connections, no records are returned.
Example usage of the function:
<screen>
postgres=# SELECT * FROM postgres_fdw_get_connections() ORDER BY 1;
@ -799,7 +791,46 @@ postgres=# SELECT * FROM postgres_fdw_get_connections() ORDER BY 1;
loopback1 | t
loopback2 | f
</screen>
The output columns are described in
<xref linkend="postgres-fdw-get-connections-columns"/>.
</para>
<table id="postgres-fdw-get-connections-columns">
<title><function>postgres_fdw_get_connections</function> Output Columns</title>
<tgroup cols="3">
<thead>
<row>
<entry>Column</entry>
<entry>Type</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry><structfield>server_name</structfield></entry>
<entry><type>text</type></entry>
<entry>
The foreign server name of this connection. If the server is
dropped but the connection remains open (i.e., marked as
invalid), this will be <literal>NULL</literal>.
</entry>
</row>
<row>
<entry><structfield>valid</structfield></entry>
<entry><type>boolean</type></entry>
<entry>
False if this connection is invalid, meaning it is used in
the current transaction, but its foreign server or
user mapping has been changed or dropped.
The invalid connection will be closed at the end of
the transaction. True is returned otherwise.
</entry>
</row>
</tbody>
</tgroup>
</table>
</listitem>
</varlistentry>