From b1051379bfdf4a1803dbf2109dfeac6b283ae457 Mon Sep 17 00:00:00 2001
From: "houzj.fnst" <houzj.fnst@cn.fujitsu.com>
Date: Thu, 11 Aug 2022 11:49:08 +0800
Subject: [PATCH v21 5/5] Add a main_worker_pid to pg_stat_subscription

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

The new column can make it easier to distinguish main apply worker and apply
background worker.

---
 doc/src/sgml/monitoring.sgml               | 11 +++++++++++
 src/backend/catalog/system_views.sql       |  1 +
 src/backend/replication/logical/launcher.c | 28 +++++++++++++++++-----------
 src/include/catalog/pg_proc.dat            |  6 +++---
 src/test/regress/expected/rules.out        |  3 ++-
 5 files changed, 34 insertions(+), 15 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index a6e7e3b..0c14709 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -3180,6 +3180,17 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>main_worker_pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of the main apply worker, if this process is a apply
+       background worker. NULL if this process is a main 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>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 8284cdd..ecd08dd 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -947,6 +947,7 @@ CREATE VIEW pg_stat_subscription AS
             su.oid AS subid,
             su.subname,
             st.pid,
+            st.main_worker_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 825e756..5a92701 100644
--- a/src/backend/replication/logical/launcher.c
+++ b/src/backend/replication/logical/launcher.c
@@ -1010,7 +1010,7 @@ 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;
@@ -1044,26 +1044,32 @@ pg_stat_get_subscription(PG_FUNCTION_ARGS)
 		else
 			nulls[1] = true;
 		values[2] = Int32GetDatum(worker_pid);
-		if (XLogRecPtrIsInvalid(worker.last_lsn))
+
+		if (worker.main_worker_pid == 0)
 			nulls[3] = true;
 		else
-			values[3] = LSNGetDatum(worker.last_lsn);
-		if (worker.last_send_time == 0)
+			values[3] = Int32GetDatum(worker.main_worker_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 be47583..b7fa2c1 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5393,9 +5393,9 @@
   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,main_worker_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 7ec3d26..be12c62 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -2091,6 +2091,7 @@ pg_stat_ssl| SELECT s.pid,
 pg_stat_subscription| SELECT su.oid AS subid,
     su.subname,
     st.pid,
+    st.main_worker_pid,
     st.relid,
     st.received_lsn,
     st.last_msg_send_time,
@@ -2098,7 +2099,7 @@ 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, main_worker_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,
-- 
2.7.2.windows.1

