Add worker type to pg_stat_subscription.

Thanks to commit 2a8b40e368, the logical replication worker type is
easily determined.  The worker type could already be deduced via
other columns such as leader_pid and relid, but that is unnecessary
complexity for users.

Bumps catversion.

Author: Peter Smith
Reviewed-by: Michael Paquier, Maxim Orlov, Amit Kapila
Discussion: https://postgr.es/m/CAHut%2BPtmbSMfErSk0S7xxVdZJ9XVE3xVLhqBTmT91kf57BeKDQ%40mail.gmail.com

doc/src/sgml/monitoring.sgml

@@ -1993,6 +1993,17 @@ description | Waiting for a newly initialized WAL file to reach durable storage
       </para></entry>
      </row>
 
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>worker_type</structfield> <type>text</type>
+      </para>
+      <para>
+       Type of the subscription worker process.  Possible types are
+       <literal>apply</literal>, <literal>parallel apply</literal>, and
+       <literal>table synchronization</literal>.
+      </para></entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>pid</structfield> <type>integer</type>
@@ -2008,7 +2019,7 @@ description | Waiting for a newly initialized WAL file to reach durable storage
       </para>
       <para>
        Process ID of the leader apply worker if this process is a parallel
-       apply worker; NULL if this process is a leader apply worker or a
+       apply worker; NULL if this process is a leader apply worker or a table
        synchronization worker
       </para></entry>
      </row>

src/backend/catalog/system_views.sql

@@ -949,6 +949,7 @@ CREATE VIEW pg_stat_subscription AS
     SELECT
             su.oid AS subid,
             su.subname,
+            st.worker_type,
             st.pid,
             st.leader_pid,
             st.relid,

src/backend/replication/logical/launcher.c

@@ -1278,7 +1278,7 @@ GetLeaderApplyWorkerPid(pid_t pid)
 Datum
 pg_stat_get_subscription(PG_FUNCTION_ARGS)
 {
-#define PG_STAT_GET_SUBSCRIPTION_COLS	9
+#define PG_STAT_GET_SUBSCRIPTION_COLS	10
 	Oid			subid = PG_ARGISNULL(0) ? InvalidOid : PG_GETARG_OID(0);
 	int			i;
 	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
@@ -1339,6 +1339,22 @@ pg_stat_get_subscription(PG_FUNCTION_ARGS)
 		else
 			values[8] = TimestampTzGetDatum(worker.reply_time);
 
+		switch (worker.type)
+		{
+			case WORKERTYPE_APPLY:
+				values[9] = CStringGetTextDatum("apply");
+				break;
+			case WORKERTYPE_PARALLEL_APPLY:
+				values[9] = CStringGetTextDatum("parallel apply");
+				break;
+			case WORKERTYPE_TABLESYNC:
+				values[9] = CStringGetTextDatum("table synchronization");
+				break;
+			case WORKERTYPE_UNKNOWN:
+				/* Should never happen. */
+				elog(ERROR, "unknown worker type");
+		}
+
 		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc,
 							 values, nulls);
 

src/include/catalog/catversion.h

@@ -57,6 +57,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	202309221
+#define CATALOG_VERSION_NO	202309251
 
 #endif

src/include/catalog/pg_proc.dat

@@ -5484,9 +5484,9 @@
   proname => 'pg_stat_get_subscription', prorows => '10', proisstrict => 'f',
   proretset => 't', provolatile => 's', proparallel => 'r',
   prorettype => 'record', proargtypes => 'oid',
-  proallargtypes => '{oid,oid,oid,int4,int4,pg_lsn,timestamptz,timestamptz,pg_lsn,timestamptz}',
-  proargmodes => '{i,o,o,o,o,o,o,o,o,o}',
-  proargnames => '{subid,subid,relid,pid,leader_pid,received_lsn,last_msg_send_time,last_msg_receipt_time,latest_end_lsn,latest_end_time}',
+  proallargtypes => '{oid,oid,oid,int4,int4,pg_lsn,timestamptz,timestamptz,pg_lsn,timestamptz,text}',
+  proargmodes => '{i,o,o,o,o,o,o,o,o,o,o}',
+  proargnames => '{subid,subid,relid,pid,leader_pid,received_lsn,last_msg_send_time,last_msg_receipt_time,latest_end_lsn,latest_end_time,worker_type}',
   prosrc => 'pg_stat_get_subscription' },
 { oid => '2026', descr => 'statistics: current backend PID',
   proname => 'pg_backend_pid', provolatile => 's', proparallel => 'r',

src/test/regress/expected/rules.out

@@ -2118,6 +2118,7 @@ pg_stat_ssl| SELECT pid,
   WHERE (client_port IS NOT NULL);
 pg_stat_subscription| SELECT su.oid AS subid,
     su.subname,
+    st.worker_type,
     st.pid,
     st.leader_pid,
     st.relid,
@@ -2127,7 +2128,7 @@ pg_stat_subscription| SELECT su.oid AS subid,
     st.latest_end_lsn,
     st.latest_end_time
    FROM (pg_subscription su
-     LEFT JOIN pg_stat_get_subscription(NULL::oid) st(subid, relid, pid, leader_pid, received_lsn, last_msg_send_time, last_msg_receipt_time, latest_end_lsn, latest_end_time) ON ((st.subid = su.oid)));
+     LEFT JOIN pg_stat_get_subscription(NULL::oid) st(subid, relid, pid, leader_pid, received_lsn, last_msg_send_time, last_msg_receipt_time, latest_end_lsn, latest_end_time, worker_type) ON ((st.subid = su.oid)));
 pg_stat_subscription_stats| SELECT ss.subid,
     s.subname,
     ss.apply_error_count,

src/test/subscription/t/004_sync.pl

@@ -80,7 +80,7 @@ $node_subscriber->safe_psql('postgres',
 
 # wait for it to start
 $node_subscriber->poll_query_until('postgres',
-	"SELECT pid IS NOT NULL FROM pg_stat_subscription WHERE subname = 'tap_sub2' AND relid IS NULL"
+	"SELECT pid IS NOT NULL FROM pg_stat_subscription WHERE subname = 'tap_sub2' AND worker_type = 'apply'"
 ) or die "Timed out while waiting for subscriber to start";
 
 # and drop both subscriptions