From dcc7c575bdddc671bcf3c5620c56f1bc28f64fb8 Mon Sep 17 00:00:00 2001
From: "houzj.fnst" <houzj.fnst@cn.fujitsu.com>
Date: Thu, 6 Oct 2022 14:42:24 +0800
Subject: [PATCH v41 6/6] Add a main_worker_pid to pg_stat_subscription

main_worker_pid is Process ID of the leader apply worker, if this process is a
apply parallel worker. NULL if this process is a leader apply worker or a
synchronization worker.

The new column can make it easier to distinguish leader apply worker and apply
parallel worker which is also similar to the 'leader_pid' column in
pg_stat_activity.
---
 doc/src/sgml/monitoring.sgml               | 26 ++++++++++++++----
 src/backend/catalog/system_views.sql       |  1 +
 src/backend/replication/logical/launcher.c | 32 ++++++++++++----------
 src/include/catalog/pg_proc.dat            |  6 ++--
 src/test/regress/expected/rules.out        |  3 +-
 5 files changed, 43 insertions(+), 25 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index e5d622d514..8726530d28 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -3178,13 +3178,24 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
       </para></entry>
      </row>
 
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>apply_leader_pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of the leader apply worker, if this process is a apply
+       parallel worker. NULL if this process is a leader apply worker or a
+       synchronization worker.
+      </para></entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>relid</structfield> <type>oid</type>
       </para>
       <para>
        OID of the relation that the worker is synchronizing; null for the
-       main apply worker
+       main apply worker and the parallel apply worker
       </para></entry>
      </row>
 
@@ -3194,7 +3205,7 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
       </para>
       <para>
        Last write-ahead log location received, the initial value of
-       this field being 0
+       this field being 0; null for the parallel apply worker
       </para></entry>
      </row>
 
@@ -3203,7 +3214,8 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
        <structfield>last_msg_send_time</structfield> <type>timestamp with time zone</type>
       </para>
       <para>
-       Send time of last message received from origin WAL sender
+       Send time of last message received from origin WAL sender; null for the
+       parallel apply worker
       </para></entry>
      </row>
 
@@ -3212,7 +3224,8 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
        <structfield>last_msg_receipt_time</structfield> <type>timestamp with time zone</type>
       </para>
       <para>
-       Receipt time of last message received from origin WAL sender
+       Receipt time of last message received from origin WAL sender; null for
+       the parallel apply worker
       </para></entry>
      </row>
 
@@ -3221,7 +3234,8 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
        <structfield>latest_end_lsn</structfield> <type>pg_lsn</type>
       </para>
       <para>
-       Last write-ahead log location reported to origin WAL sender
+       Last write-ahead log location reported to origin WAL sender; null for
+       the parallel apply worker
       </para></entry>
      </row>
 
@@ -3231,7 +3245,7 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
       </para>
       <para>
        Time of last write-ahead log location reported to origin WAL
-       sender
+       sender; null for the parallel apply worker
       </para></entry>
      </row>
     </tbody>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index c2c7d8a8b7..f2825705f1 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -949,6 +949,7 @@ CREATE VIEW pg_stat_subscription AS
             su.oid AS subid,
             su.subname,
             st.pid,
+            st.apply_leader_pid,
             st.relid,
             st.received_lsn,
             st.last_msg_send_time,
diff --git a/src/backend/replication/logical/launcher.c b/src/backend/replication/logical/launcher.c
index 66ca19f43d..20e0232468 100644
--- a/src/backend/replication/logical/launcher.c
+++ b/src/backend/replication/logical/launcher.c
@@ -1058,7 +1058,7 @@ IsLogicalLauncher(void)
 Datum
 pg_stat_get_subscription(PG_FUNCTION_ARGS)
 {
-#define PG_STAT_GET_SUBSCRIPTION_COLS	8
+#define PG_STAT_GET_SUBSCRIPTION_COLS	9
 	Oid			subid = PG_ARGISNULL(0) ? InvalidOid : PG_GETARG_OID(0);
 	int			i;
 	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
@@ -1084,10 +1084,6 @@ pg_stat_get_subscription(PG_FUNCTION_ARGS)
 		if (OidIsValid(subid) && worker.subid != subid)
 			continue;
 
-		/* Skip if this is a parallel apply worker */
-		if (isParallelApplyWorker(&worker))
-			continue;
-
 		worker_pid = worker.proc->pid;
 
 		values[0] = ObjectIdGetDatum(worker.subid);
@@ -1096,26 +1092,32 @@ pg_stat_get_subscription(PG_FUNCTION_ARGS)
 		else
 			nulls[1] = true;
 		values[2] = Int32GetDatum(worker_pid);
-		if (XLogRecPtrIsInvalid(worker.last_lsn))
+
+		if (worker.apply_leader_pid == InvalidPid)
 			nulls[3] = true;
 		else
-			values[3] = LSNGetDatum(worker.last_lsn);
-		if (worker.last_send_time == 0)
+			values[3] = Int32GetDatum(worker.apply_leader_pid);
+
+		if (XLogRecPtrIsInvalid(worker.last_lsn))
 			nulls[4] = true;
 		else
-			values[4] = TimestampTzGetDatum(worker.last_send_time);
-		if (worker.last_recv_time == 0)
+			values[4] = LSNGetDatum(worker.last_lsn);
+		if (worker.last_send_time == 0)
 			nulls[5] = true;
 		else
-			values[5] = TimestampTzGetDatum(worker.last_recv_time);
-		if (XLogRecPtrIsInvalid(worker.reply_lsn))
+			values[5] = TimestampTzGetDatum(worker.last_send_time);
+		if (worker.last_recv_time == 0)
 			nulls[6] = true;
 		else
-			values[6] = LSNGetDatum(worker.reply_lsn);
-		if (worker.reply_time == 0)
+			values[6] = TimestampTzGetDatum(worker.last_recv_time);
+		if (XLogRecPtrIsInvalid(worker.reply_lsn))
 			nulls[7] = true;
 		else
-			values[7] = TimestampTzGetDatum(worker.reply_time);
+			values[7] = LSNGetDatum(worker.reply_lsn);
+		if (worker.reply_time == 0)
+			nulls[8] = true;
+		else
+			values[8] = TimestampTzGetDatum(worker.reply_time);
 
 		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc,
 							 values, nulls);
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 62a5b8e655..fd8469ef1f 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5400,9 +5400,9 @@
   proname => 'pg_stat_get_subscription', prorows => '10', proisstrict => 'f',
   proretset => 't', provolatile => 's', proparallel => 'r',
   prorettype => 'record', proargtypes => 'oid',
-  proallargtypes => '{oid,oid,oid,int4,pg_lsn,timestamptz,timestamptz,pg_lsn,timestamptz}',
-  proargmodes => '{i,o,o,o,o,o,o,o,o}',
-  proargnames => '{subid,subid,relid,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}',
+  proargmodes => '{i,o,o,o,o,o,o,o,o,o}',
+  proargnames => '{subid,subid,relid,pid,apply_leader_pid,received_lsn,last_msg_send_time,last_msg_receipt_time,latest_end_lsn,latest_end_time}',
   prosrc => 'pg_stat_get_subscription' },
 { oid => '2026', descr => 'statistics: current backend PID',
   proname => 'pg_backend_pid', provolatile => 's', proparallel => 'r',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index bfcd8ac9a0..bef75f66f9 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -2089,6 +2089,7 @@ pg_stat_ssl| SELECT s.pid,
 pg_stat_subscription| SELECT su.oid AS subid,
     su.subname,
     st.pid,
+    st.apply_leader_pid,
     st.relid,
     st.received_lsn,
     st.last_msg_send_time,
@@ -2096,7 +2097,7 @@ 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, 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, apply_leader_pid, received_lsn, last_msg_send_time, last_msg_receipt_time, latest_end_lsn, latest_end_time) ON ((st.subid = su.oid)));
 pg_stat_subscription_stats| SELECT ss.subid,
     s.subname,
     ss.apply_error_count,
-- 
2.23.0.windows.1

