/* Number of output arguments (columns) for various API versions */
#define POSTGRES_FDW_GET_CONNECTIONS_COLS_V1_1 2
-#define POSTGRES_FDW_GET_CONNECTIONS_COLS_V1_2 5
-#define POSTGRES_FDW_GET_CONNECTIONS_COLS 5 /* maximum of above */
+#define POSTGRES_FDW_GET_CONNECTIONS_COLS_V1_2 6
+#define POSTGRES_FDW_GET_CONNECTIONS_COLS 6 /* maximum of above */
/*
* Internal function used by postgres_fdw_get_connections variants.
*
* For API version 1.2 and later, this function takes an input parameter
* to check a connection status and returns the following
- * additional values along with the three values from version 1.1:
+ * additional values along with the four values from version 1.1:
*
* - user_name - the local user name of the active connection. In case the
* user mapping is dropped but the connection is still active, then the
* user name will be NULL in the output.
* - used_in_xact - true if the connection is used in the current transaction.
* - closed - true if the connection is closed.
+ * - remote_backend_pid - process ID of the remote backend, on the foreign
+ * server, handling the connection.
*
* No records are returned when there are no cached connections at all.
*/
values[i++] = BoolGetDatum(pgfdw_conn_check(entry->conn) != 0);
else
nulls[i++] = true;
+
+ /* Return process ID of remote backend */
+ values[i++] = Int32GetDatum(PQbackendPID(entry->conn));
}
tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
-- List all the existing cached connections. loopback and loopback3
-- should be output as invalid connections. Also the server name and user name
-- for loopback3 should be NULL because both server and user mapping were
--- dropped.
-SELECT server_name, user_name = CURRENT_USER as "user_name = CURRENT_USER", valid, used_in_xact, closed
-FROM postgres_fdw_get_connections() ORDER BY 1;
- server_name | user_name = CURRENT_USER | valid | used_in_xact | closed
--------------+--------------------------+-------+--------------+--------
- loopback | t | f | t |
- | | f | t |
+-- dropped. In this test, the PIDs of remote backends can be gathered from
+-- pg_stat_activity, and remote_backend_pid should match one of those PIDs.
+SELECT server_name, user_name = CURRENT_USER as "user_name = CURRENT_USER",
+ valid, used_in_xact, closed,
+ remote_backend_pid = ANY(SELECT pid FROM pg_stat_activity
+ WHERE backend_type = 'client backend' AND pid <> pg_backend_pid())
+ as remote_backend_pid
+ FROM postgres_fdw_get_connections() ORDER BY 1;
+ server_name | user_name = CURRENT_USER | valid | used_in_xact | closed | remote_backend_pid
+-------------+--------------------------+-------+--------------+--------+--------------------
+ loopback | t | f | t | | t
+ | | f | t | | t
(2 rows)
-- The invalid connections get closed in pgfdw_xact_callback during commit.
-- Since the remote server is still connected, "closed" should be FALSE,
-- or NULL if the connection status check is not available.
-SELECT CASE WHEN closed IS NOT true THEN 1 ELSE 0 END
+-- In this test, the remote backend handling this connection should have
+-- application_name set to "fdw_conn_check", so remote_backend_pid should
+-- match the PID from the pg_stat_activity entry with that application_name.
+SELECT server_name,
+ CASE WHEN closed IS NOT true THEN false ELSE true END AS closed,
+ remote_backend_pid = (SELECT pid FROM pg_stat_activity
+ WHERE application_name = 'fdw_conn_check') AS remote_backend_pid
FROM postgres_fdw_get_connections(true);
- case
-------
- 1
+ server_name | closed | remote_backend_pid
+-------------+--------+--------------------
+ loopback | f | t
(1 row)
-- After terminating the remote backend, since the connection is closed,
-- "closed" should be TRUE, or NULL if the connection status check
--- is not available.
+-- is not available. Despite the termination, remote_backend_pid should
+-- still show the non-zero PID of the terminated remote backend.
DO $$ BEGIN
PERFORM pg_terminate_backend(pid, 180000) FROM pg_stat_activity
WHERE application_name = 'fdw_conn_check';
END $$;
-SELECT CASE WHEN closed IS NOT false THEN 1 ELSE 0 END
+SELECT server_name,
+ CASE WHEN closed IS NOT false THEN true ELSE false END AS closed,
+ remote_backend_pid <> 0 AS remote_backend_pid
FROM postgres_fdw_get_connections(true);
- case
-------
- 1
+ server_name | closed | remote_backend_pid
+-------------+--------+--------------------
+ loopback | t | t
(1 row)
-- Clean up
CREATE FUNCTION postgres_fdw_get_connections (
IN check_conn boolean DEFAULT false, OUT server_name text,
OUT user_name text, OUT valid boolean, OUT used_in_xact boolean,
- OUT closed boolean)
+ OUT closed boolean, OUT remote_backend_pid int4)
RETURNS SETOF record
AS 'MODULE_PATHNAME', 'postgres_fdw_get_connections_1_2'
LANGUAGE C STRICT PARALLEL RESTRICTED;
-- List all the existing cached connections. loopback and loopback3
-- should be output as invalid connections. Also the server name and user name
-- for loopback3 should be NULL because both server and user mapping were
--- dropped.
-SELECT server_name, user_name = CURRENT_USER as "user_name = CURRENT_USER", valid, used_in_xact, closed
-FROM postgres_fdw_get_connections() ORDER BY 1;
+-- dropped. In this test, the PIDs of remote backends can be gathered from
+-- pg_stat_activity, and remote_backend_pid should match one of those PIDs.
+SELECT server_name, user_name = CURRENT_USER as "user_name = CURRENT_USER",
+ valid, used_in_xact, closed,
+ remote_backend_pid = ANY(SELECT pid FROM pg_stat_activity
+ WHERE backend_type = 'client backend' AND pid <> pg_backend_pid())
+ as remote_backend_pid
+ FROM postgres_fdw_get_connections() ORDER BY 1;
-- The invalid connections get closed in pgfdw_xact_callback during commit.
COMMIT;
-- All cached connections were closed while committing above xact, so no
-- Since the remote server is still connected, "closed" should be FALSE,
-- or NULL if the connection status check is not available.
-SELECT CASE WHEN closed IS NOT true THEN 1 ELSE 0 END
+-- In this test, the remote backend handling this connection should have
+-- application_name set to "fdw_conn_check", so remote_backend_pid should
+-- match the PID from the pg_stat_activity entry with that application_name.
+SELECT server_name,
+ CASE WHEN closed IS NOT true THEN false ELSE true END AS closed,
+ remote_backend_pid = (SELECT pid FROM pg_stat_activity
+ WHERE application_name = 'fdw_conn_check') AS remote_backend_pid
FROM postgres_fdw_get_connections(true);
-- After terminating the remote backend, since the connection is closed,
-- "closed" should be TRUE, or NULL if the connection status check
--- is not available.
+-- is not available. Despite the termination, remote_backend_pid should
+-- still show the non-zero PID of the terminated remote backend.
DO $$ BEGIN
PERFORM pg_terminate_backend(pid, 180000) FROM pg_stat_activity
WHERE application_name = 'fdw_conn_check';
END $$;
-SELECT CASE WHEN closed IS NOT false THEN 1 ELSE 0 END
+SELECT server_name,
+ CASE WHEN closed IS NOT false THEN true ELSE false END AS closed,
+ remote_backend_pid <> 0 AS remote_backend_pid
FROM postgres_fdw_get_connections(true);
-- Clean up
<term><function>postgres_fdw_get_connections(
IN check_conn boolean DEFAULT false, OUT server_name text,
OUT user_name text, OUT valid boolean, OUT used_in_xact boolean,
- OUT closed boolean)
+ OUT closed boolean, OUT remote_backend_pid int4)
returns setof record</function></term>
<listitem>
<para>
Example usage of the function:
<screen>
postgres=# SELECT * FROM postgres_fdw_get_connections(true);
- server_name | user_name | valid | used_in_xact | closed
--------------+-----------+-------+--------------+--------
- loopback1 | postgres | t | t | f
- loopback2 | public | t | t | f
- loopback3 | | f | t | f
+ server_name | user_name | valid | used_in_xact | closed | remote_backend_pid
+-------------+-----------+-------+--------------+-----------------------------
+ loopback1 | postgres | t | t | f | 1353340
+ loopback2 | public | t | t | f | 1353120
+ loopback3 | | f | t | f | 1353156
</screen>
The output columns are described in
<xref linkend="postgres-fdw-get-connections-columns"/>.
is not available on this platform.
</entry>
</row>
+ <row>
+ <entry><structfield>remote_backend_pid</structfield></entry>
+ <entry><type>int4</type></entry>
+ <entry>
+ Process ID of the remote backend, on the foreign server,
+ handling the connection. If the remote backend is terminated and
+ the connection is closed (with <literal>closed</literal> set to
+ <literal>true</literal>), this still shows the process ID of
+ the terminated backend.
+ </entry>
+ </row>
</tbody>
</tgroup>
</table>
projects / postgresql.git / commitdiff