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Tom Lane wrote:
> [ thinks for awhile... ] Actually, it seems to me that the present
> patch's definition of the function would be very hard to work with.
> You would normally want to work with the events one at a time.
> There isn't much you could do with the array result except unnest() it,
> and I'm a bit worried that careless usage could result in multiple
> evaluation of the function and hence loss of events. I wonder whether
> it would be better to have the function return setof record. Which, not
> incidentally, would greatly simplify adding in those extra result
> fields.
OK, how's this look?
Joe
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Index: contrib/dblink/dblink.c
===================================================================
RCS file: /opt/src/cvs/pgsql/contrib/dblink/dblink.c,v
retrieving revision 1.82
diff -c -r1.82 dblink.c
*** contrib/dblink/dblink.c 11 Jun 2009 14:48:50 -0000 1.82
--- contrib/dblink/dblink.c 4 Aug 2009 03:48:33 -0000
***************
*** 1635,1640 ****
--- 1635,1723 ----
PG_RETURN_DATUM(current_query(fcinfo));
}
+ /*
+ * Retrieve async notifications for a connection.
+ *
+ * Returns an setof record of notifications, or an empty set if none recieved.
+ * Can optionally take a named connection as parameter, but uses the unnamed connection per default.
+ *
+ */
+ #define DBLINK_NOTIFY_COLS 3
+
+ PG_FUNCTION_INFO_V1(dblink_get_notify);
+ Datum
+ dblink_get_notify(PG_FUNCTION_ARGS)
+ {
+ PGconn *conn = NULL;
+ remoteConn *rconn = NULL;
+ PGnotify *notify;
+ ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+ TupleDesc tupdesc;
+ Tuplestorestate *tupstore;
+ MemoryContext per_query_ctx;
+ MemoryContext oldcontext;
+
+ DBLINK_INIT;
+ if (PG_NARGS() == 1)
+ DBLINK_GET_NAMED_CONN;
+ else
+ conn = pconn->conn;
+
+ /* create the tuplestore */
+ per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
+ oldcontext = MemoryContextSwitchTo(per_query_ctx);
+
+ tupdesc = CreateTemplateTupleDesc(DBLINK_NOTIFY_COLS, false);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "notify_name",
+ TEXTOID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "be_pid",
+ INT4OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "extra",
+ TEXTOID, -1, 0);
+
+ tupstore = tuplestore_begin_heap(true, false, work_mem);
+ rsinfo->returnMode = SFRM_Materialize;
+ rsinfo->setResult = tupstore;
+ rsinfo->setDesc = tupdesc;
+
+ MemoryContextSwitchTo(oldcontext);
+
+ PQconsumeInput(conn);
+ while ((notify = PQnotifies(conn)) != NULL)
+ {
+ Datum values[DBLINK_NOTIFY_COLS];
+ bool nulls[DBLINK_NOTIFY_COLS];
+
+ memset(values, 0, sizeof(values));
+ memset(nulls, 0, sizeof(nulls));
+
+ if (notify->relname != NULL)
+ values[0] = CStringGetTextDatum(notify->relname);
+ else
+ nulls[0] = true;
+
+ values[1] = Int32GetDatum(notify->be_pid);
+
+ if (notify->extra != NULL)
+ values[2] = CStringGetTextDatum(notify->extra);
+ else
+ nulls[2] = true;
+
+ /* switch to appropriate context while storing the tuple */
+ MemoryContextSwitchTo(per_query_ctx);
+ tuplestore_putvalues(tupstore, tupdesc, values, nulls);
+ MemoryContextSwitchTo(oldcontext);
+
+ PQfreemem(notify);
+ PQconsumeInput(conn);
+ }
+
+ /* clean up and return the tuplestore */
+ tuplestore_donestoring(tupstore);
+
+ return (Datum) 0;
+ }
+
/*************************************************************
* internal functions
*/
Index: contrib/dblink/dblink.h
===================================================================
RCS file: /opt/src/cvs/pgsql/contrib/dblink/dblink.h,v
retrieving revision 1.22
diff -c -r1.22 dblink.h
*** contrib/dblink/dblink.h 9 Jun 2009 17:41:02 -0000 1.22
--- contrib/dblink/dblink.h 4 Aug 2009 02:35:59 -0000
***************
*** 57,61 ****
--- 57,62 ----
extern Datum dblink_build_sql_delete(PG_FUNCTION_ARGS);
extern Datum dblink_build_sql_update(PG_FUNCTION_ARGS);
extern Datum dblink_current_query(PG_FUNCTION_ARGS);
+ extern Datum dblink_get_notify(PG_FUNCTION_ARGS);
#endif /* DBLINK_H */
Index: contrib/dblink/dblink.sql.in
===================================================================
RCS file: /opt/src/cvs/pgsql/contrib/dblink/dblink.sql.in,v
retrieving revision 1.18
diff -c -r1.18 dblink.sql.in
*** contrib/dblink/dblink.sql.in 9 Jun 2009 17:41:02 -0000 1.18
--- contrib/dblink/dblink.sql.in 4 Aug 2009 03:51:03 -0000
***************
*** 202,204 ****
--- 202,221 ----
RETURNS text
AS 'MODULE_PATHNAME', 'dblink_error_message'
LANGUAGE C STRICT;
+
+ CREATE TYPE dblink_get_notify_type AS
+ (
+ notify_name TEXT,
+ be_pid INT4,
+ extra TEXT
+ );
+
+ CREATE OR REPLACE FUNCTION dblink_get_notify()
+ RETURNS setof dblink_get_notify_type
+ AS 'MODULE_PATHNAME', 'dblink_get_notify'
+ LANGUAGE C STRICT;
+
+ CREATE OR REPLACE FUNCTION dblink_get_notify(conname text)
+ RETURNS setof dblink_get_notify_type
+ AS 'MODULE_PATHNAME', 'dblink_get_notify'
+ LANGUAGE C STRICT;
Index: contrib/dblink/uninstall_dblink.sql
===================================================================
RCS file: /opt/src/cvs/pgsql/contrib/dblink/uninstall_dblink.sql,v
retrieving revision 1.7
diff -c -r1.7 uninstall_dblink.sql
*** contrib/dblink/uninstall_dblink.sql 5 Apr 2008 02:26:14 -0000 1.7
--- contrib/dblink/uninstall_dblink.sql 4 Aug 2009 02:35:59 -0000
***************
*** 76,78 ****
--- 76,82 ----
DROP FUNCTION dblink_is_busy(text);
DROP FUNCTION dblink_send_query(text, text);
+
+ DROP FUNCTION dblink_get_notify();
+
+ DROP FUNCTION dblink_get_notify(text);
Index: contrib/dblink/expected/dblink.out
===================================================================
RCS file: /opt/src/cvs/pgsql/contrib/dblink/expected/dblink.out,v
retrieving revision 1.25
diff -c -r1.25 dblink.out
*** contrib/dblink/expected/dblink.out 6 Jun 2009 21:27:56 -0000 1.25
--- contrib/dblink/expected/dblink.out 4 Aug 2009 04:07:05 -0000
***************
*** 827,829 ****
--- 827,870 ----
DROP USER MAPPING FOR public SERVER fdtest;
DROP SERVER fdtest;
DROP FOREIGN DATA WRAPPER postgresql;
+ -- 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 listen
+ SELECT dblink_exec('LISTEN foobar');
+ dblink_exec
+ -------------
+ LISTEN
+ (1 row)
+
+ NOTIFY regression;
+ NOTIFY foobar;
+ SELECT notify_name, be_pid/be_pid as be_pid, extra from dblink_get_notify();
+ notify_name | be_pid | extra
+ -------------+--------+-------
+ regression | 1 |
+ foobar | 1 |
+ (2 rows)
+
+ SELECT * from dblink_get_notify();
+ notify_name | be_pid | extra
+ -------------+--------+-------
+ (0 rows)
+
+ SELECT dblink_disconnect();
+ dblink_disconnect
+ -------------------
+ OK
+ (1 row)
+
Index: contrib/dblink/sql/dblink.sql
===================================================================
RCS file: /opt/src/cvs/pgsql/contrib/dblink/sql/dblink.sql,v
retrieving revision 1.21
diff -c -r1.21 dblink.sql
*** contrib/dblink/sql/dblink.sql 6 Jun 2009 21:27:56 -0000 1.21
--- contrib/dblink/sql/dblink.sql 4 Aug 2009 04:06:37 -0000
***************
*** 389,391 ****
--- 389,408 ----
DROP USER MAPPING FOR public SERVER fdtest;
DROP SERVER fdtest;
DROP FOREIGN DATA WRAPPER postgresql;
+
+ -- test asynchronous notifications
+ SELECT dblink_connect('dbname=contrib_regression');
+
+ --should return listen
+ SELECT dblink_exec('LISTEN regression');
+ --should return listen
+ SELECT dblink_exec('LISTEN foobar');
+
+ NOTIFY regression;
+ NOTIFY foobar;
+
+ SELECT notify_name, be_pid/be_pid as be_pid, extra from dblink_get_notify();
+
+ SELECT * from dblink_get_notify();
+
+ SELECT dblink_disconnect();
Index: doc/src/sgml/dblink.sgml
===================================================================
RCS file: /opt/src/cvs/pgsql/doc/src/sgml/dblink.sgml,v
retrieving revision 1.8
diff -c -r1.8 dblink.sgml
*** doc/src/sgml/dblink.sgml 18 Jun 2009 14:34:36 -0000 1.8
--- doc/src/sgml/dblink.sgml 4 Aug 2009 04:13:45 -0000
***************
*** 1260,1265 ****
--- 1260,1338 ----
</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 setof (notify_name text, be_pid int, extra text)
+ dblink_get_notify(text connname) returns setof (notify_name text, be_pid int, extra 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 receive 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 setof (notify_name text, be_pid int, extra text), or an empty set if none.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Example</title>
+
+ <programlisting>
+ test=# SELECT dblink_exec('LISTEN virtual');
+ dblink_exec
+ -------------
+ LISTEN
+ (1 row)
+
+ test=# SELECT * FROM dblink_get_notify();
+ notify_name | be_pid | extra
+ -------------+--------+-------
+ (0 rows)
+
+ test=# NOTIFY virtual;
+ NOTIFY
+
+ SELECT * FROM dblink_get_notify();
+ notify_name | be_pid | extra
+ -------------+--------+-------
+ virtual | 1229 |
+ (1 row)
+ </programlisting>
+ </refsect1>
+ </refentry>
+
<refentry id="CONTRIB-DBLINK-GET-RESULT">
<refmeta>
<refentrytitle>dblink_get_result</refentrytitle>
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