This patch adds the ability to retrieve async notifications using dblink,
via the addition of the function dblink_get_notify.
It is written against cvs head, includes documentation and regression
testing. It compiles, tests and works well.
I would be interested in some feedback on the regression test.
My initial thought was to test the function as thoroughly as possible. So I
perform listen and notify commands within the test to be able to test all
aspects of the code. Even though this works well for me, I get the feeling
that this is not the correct way to do it. I can find no other testing of
the listen/notify functionality in the regression tests, and I imagine this
is for good reason.
If someone would care to explain this, and maybe give a hint about what
amount of testing is appropriate for this fairly trivial patch, it would be
appreciated.
Best regards,
Marcus Kempe
*** ./pgsql/contrib/dblink/dblink.c.orig 2008-11-17 00:23:45.000000000 +0100
--- ./pgsql/contrib/dblink/dblink.c 2008-11-18 23:21:39.000000000 +0100
***************
*** 1597,1602 ****
--- 1597,1644 ----
PG_RETURN_TEXT_P(cstring_to_text(sql));
}
+
+ /*
+ * Retrieve async notifications for a connection.
+ *
+ * Returns an array of notifications, or NULL if none recieved.
+ * Can optionally take a named connection as parameter, but uses the unnamed connection per default.
+ *
+ */
+ PG_FUNCTION_INFO_V1(dblink_get_notify);
+ Datum
+ dblink_get_notify(PG_FUNCTION_ARGS)
+ {
+ PGconn *conn = NULL;
+ remoteConn *rconn = NULL;
+ ArrayBuildState *astate = NULL;
+ PGnotify *notify;
+
+ DBLINK_INIT;
+ if (PG_NARGS() == 1)
+ DBLINK_GET_NAMED_CONN;
+ else
+ conn = pconn->conn;
+
+ PQconsumeInput(conn);
+
+ while ((notify = PQnotifies(conn)) != NULL)
+ {
+ /* stash away current value */
+ astate = accumArrayResult(astate,
+ PointerGetDatum(GET_TEXT(notify->relname)),
+ false, TEXTOID, CurrentMemoryContext);
+ PQfreemem(notify);
+ PQconsumeInput(conn);
+ }
+
+ if (astate)
+ PG_RETURN_ARRAYTYPE_P(makeArrayResult(astate,
+ CurrentMemoryContext));
+ else
+ PG_RETURN_NULL();
+ }
+
/*************************************************************
* internal functions
*/
*** ./pgsql/contrib/dblink/dblink.h.orig 2008-11-17 00:23:48.000000000 +0100
--- ./pgsql/contrib/dblink/dblink.h 2008-11-18 23:22:12.000000000 +0100
***************
*** 56,60 ****
--- 56,61 ----
extern Datum dblink_build_sql_insert(PG_FUNCTION_ARGS);
extern Datum dblink_build_sql_delete(PG_FUNCTION_ARGS);
extern Datum dblink_build_sql_update(PG_FUNCTION_ARGS);
+ extern Datum dblink_get_notify(PG_FUNCTION_ARGS);
#endif /* DBLINK_H */
*** ./pgsql/contrib/dblink/dblink.sql.in.orig 2008-11-17 00:24:28.000000000 +0100
--- ./pgsql/contrib/dblink/dblink.sql.in 2008-11-18 23:23:09.000000000 +0100
***************
*** 202,204 ****
--- 202,214 ----
RETURNS text
AS 'MODULE_PATHNAME', 'dblink_error_message'
LANGUAGE C STRICT;
+
+ CREATE OR REPLACE FUNCTION dblink_get_notify()
+ RETURNS text[]
+ AS '$libdir/dblink', 'dblink_get_notify'
+ LANGUAGE C STRICT;
+
+ CREATE OR REPLACE FUNCTION dblink_get_notify(conname text)
+ RETURNS text[]
+ AS '$libdir/dblink', 'dblink_get_notify'
+ LANGUAGE C STRICT;
*** ./pgsql/contrib/dblink/expected/dblink.out.orig 2008-11-17 00:24:04.000000000 +0100
--- ./pgsql/contrib/dblink/expected/dblink.out 2008-11-18 23:47:37.000000000 +0100
***************
*** 784,786 ****
--- 784,827 ----
OK
(1 row)
+ -- test asynchronous notifications
+ SELECT dblink_connect('dbname=contrib_regression');
+ dblink_connect
+ ----------------
+ OK
+ (1 row)
+
+ --should return listen
+ SELECT dblink_exec('LISTEN regression');
+ dblink_exec
+ -------------
+ LISTEN
+ (1 row)
+
+ --should return NOTIFY
+ SELECT dblink_exec('NOTIFY regression');
+ dblink_exec
+ -------------
+ NOTIFY
+ (1 row)
+
+ --should return {regression}
+ SELECT dblink_get_notify();
+ dblink_get_notify
+ -------------------
+ {regression}
+ (1 row)
+
+ --should return null
+ SELECT dblink_get_notify();
+ dblink_get_notify
+ -------------------
+
+ (1 row)
+
+ SELECT dblink_disconnect();
+ dblink_disconnect
+ -------------------
+ OK
+ (1 row)
+
*** ./pgsql/contrib/dblink/sql/dblink.sql.orig 2008-11-17 00:24:12.000000000 +0100
--- ./pgsql/contrib/dblink/sql/dblink.sql 2008-11-18 23:48:17.000000000 +0100
***************
*** 364,366 ****
--- 364,384 ----
SELECT dblink_cancel_query('dtest1');
SELECT dblink_error_message('dtest1');
SELECT dblink_disconnect('dtest1');
+
+ -- test asynchronous notifications
+ SELECT dblink_connect('dbname=contrib_regression');
+
+ --should return listen
+ SELECT dblink_exec('LISTEN regression');
+
+ --should return NOTIFY
+ SELECT dblink_exec('NOTIFY regression');
+
+ --should return {regression}
+ SELECT dblink_get_notify();
+
+ --should return null
+ SELECT dblink_get_notify();
+
+ SELECT dblink_disconnect();
+
*** ./pgsql/contrib/dblink/uninstall_dblink.sql.orig 2008-11-17 00:24:57.000000000 +0100
--- ./pgsql/contrib/dblink/uninstall_dblink.sql 2008-11-18 23:25:21.000000000 +0100
***************
*** 76,78 ****
--- 76,83 ----
DROP FUNCTION dblink_is_busy(text);
DROP FUNCTION dblink_send_query(text, text);
+
+ DROP FUNCTION dblink_get_notify();
+
+ DROP FUNCTION dblink_get_notify(text);
+
*** ./pgsql/doc/src/sgml/dblink.sgml.orig 2008-11-17 00:23:16.000000000 +0100
--- ./pgsql/doc/src/sgml/dblink.sgml 2008-11-18 23:55:20.000000000 +0100
***************
*** 1199,1204 ****
--- 1199,1278 ----
</refsect1>
</refentry>
+ <refentry id="CONTRIB-DBLINK-GET-NOTIFY">
+ <refnamediv>
+ <refname>dblink_get_notify</refname>
+ <refpurpose>retrieve async notifications on a connection</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <synopsis>
+ dblink_get_notify() returns text[]
+ dblink_get_notify(text connname) returns text[]
+ </synopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para>
+ <function>dblink_get_notify</> retrieves notifications on either
+ the unnamed connection, or on a named connection if specified.
+ To recieve notifications via dblink, <function>LISTEN</> must
+ first be issued, using <function>dblink_exec</>.
+ For details see <xref linkend="sql-listen"> and <xref linkend="sql-notify">.
+ </para>
+
+ </refsect1>
+
+ <refsect1>
+ <title>Arguments</title>
+
+ <variablelist>
+ <varlistentry>
+ <term><parameter>conname</parameter></term>
+ <listitem>
+ <para>
+ The name of a named connection to get notifications on.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Return Value</title>
+ <para>Returns a text array of notification names, or NULL if none.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Example</title>
+
+ <programlisting>
+ test=# SELECT dblink_exec('LISTEN virtual');
+ dblink_exec
+ -------------
+ LISTEN
+ (1 row)
+
+ test=# SELECT dblink_get_notify();
+ dblink_get_notify
+ -------------------
+
+ (1 row)
+
+ test=# NOTIFY virtual;
+ NOTIFY
+
+ test=# SELECT dblink_get_notify();
+ dblink_get_notify
+ -------------------
+ {virtual}
+ (1 row)
+ </programlisting>
+ </refsect1>
+ </refentry>
+
<refentry id="CONTRIB-DBLINK-GET-RESULT">
<refmeta>
<refentrytitle>dblink_get_result</refentrytitle>
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