diff options
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/postgres-fdw.sgml | 42 |
1 files changed, 35 insertions, 7 deletions
diff --git a/doc/src/sgml/postgres-fdw.sgml b/doc/src/sgml/postgres-fdw.sgml index b904f7a33ec..90969f63ca7 100644 --- a/doc/src/sgml/postgres-fdw.sgml +++ b/doc/src/sgml/postgres-fdw.sgml @@ -777,21 +777,39 @@ OPTIONS (ADD password_required 'false'); <variablelist> <varlistentry> - <term><function>postgres_fdw_get_connections(OUT server_name text, - OUT valid boolean, OUT used_in_xact boolean) + <term><function>postgres_fdw_get_connections( + IN check_conn boolean DEFAULT false, OUT server_name text, + OUT valid boolean, OUT used_in_xact boolean, OUT closed boolean) returns setof record</function></term> <listitem> <para> 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. + </para> + <para> + If <literal>check_conn</literal> is set to <literal>true</literal>, + the function checks the status of each connection and shows + the result in the <literal>closed</literal> column. + This feature is currently available only on systems that support + the non-standard <symbol>POLLRDHUP</symbol> extension to + the <symbol>poll</symbol> system call, including Linux. + This is useful to check if all connections used within + a transaction are still open. If any connections are closed, + the transaction cannot be committed successfully, + so it is better to roll back as soon as a closed connection is detected, + rather than continuing to the end. Users can roll back the transaction + immediately if the function reports connections where both + <literal>used_in_xact</literal> and <literal>closed</literal> are + <literal>true</literal>. + </para> + <para> Example usage of the function: <screen> -postgres=*# SELECT * FROM postgres_fdw_get_connections() ORDER BY 1; - server_name | valid | used_in_xact --------------+-------+-------------- - loopback1 | t | t - loopback2 | f | t + server_name | valid | used_in_xact | closed +-------------+-------+--------------+-------- + loopback1 | t | t | + loopback2 | f | t | </screen> The output columns are described in <xref linkend="postgres-fdw-get-connections-columns"/>. @@ -836,6 +854,16 @@ postgres=*# SELECT * FROM postgres_fdw_get_connections() ORDER BY 1; True if this connection is used in the current transaction. </entry> </row> + <row> + <entry><structfield>closed</structfield></entry> + <entry><type>boolean</type></entry> + <entry> + True if this connection is closed, false otherwise. + <literal>NULL</literal> is returned if <literal>check_conn</literal> + is set to <literal>false</literal> or if the connection status check + is not available on this platform. + </entry> + </row> </tbody> </tgroup> </table> |