From 9402f8868d64f12cf6cd7b2fea5aeec146a5c54d Mon Sep 17 00:00:00 2001
From: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Date: Tue, 19 Jul 2022 08:52:19 +0000
Subject: [PATCH v1] Add new function pg_last_wal_replay_info()

---
 src/backend/access/transam/xlogfuncs.c | 36 ++++++++++++++++++++++++++
 src/include/catalog/pg_proc.dat        |  5 ++++
 2 files changed, 41 insertions(+)

diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c
index 61e0f4a29c..db07dbb6a8 100644
--- a/src/backend/access/transam/xlogfuncs.c
+++ b/src/backend/access/transam/xlogfuncs.c
@@ -313,6 +313,42 @@ pg_last_wal_replay_lsn(PG_FUNCTION_ARGS)
 	PG_RETURN_LSN(recptr);
 }
 
+#define PG_LAST_WAL_REPLAY_INFO_COLS 2
+Datum
+pg_last_wal_replay_info(PG_FUNCTION_ARGS)
+{
+	HeapTuple	tuple;
+	TupleDesc	tupleDesc;
+	Datum		values[PG_LAST_WAL_REPLAY_INFO_COLS] = {0};
+	bool		nulls[PG_LAST_WAL_REPLAY_INFO_COLS] = {0};
+	Datum		result;
+	XLogRecPtr	recptr;
+	TimeLineID	tli;
+
+	recptr = GetXLogReplayRecPtr(&tli);
+
+	/*
+	 * Build a tuple descriptor for our result type
+	 */
+	if (get_call_result_type(fcinfo, NULL, &tupleDesc) != TYPEFUNC_COMPOSITE)
+		elog(ERROR, "return type must be a row type");
+
+	if (recptr == 0)
+		PG_RETURN_NULL();
+
+	values[0] = Int32GetDatum(recptr);
+	values[1] = Int64GetDatum(tli);
+
+	/*
+	 * Build and return the tuple
+	 */
+	tuple = heap_form_tuple(tupleDesc, values, nulls);
+	result = HeapTupleGetDatum(tuple);
+
+	PG_RETURN_DATUM(result);
+}
+#undef PG_LAST_WAL_REPLAY_INFO_COLS
+
 /*
  * Compute an xlog file name and decimal byte offset given a WAL location,
  * such as is returned by pg_backup_stop() or pg_switch_wal().
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 2e41f4d9e8..71ce3720ca 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6356,6 +6356,11 @@
   proname => 'pg_last_xact_replay_timestamp', provolatile => 'v',
   prorettype => 'timestamptz', proargtypes => '',
   prosrc => 'pg_last_xact_replay_timestamp' },
+{ oid => '9319', descr => 'get last replayed wal info such as lsn, timeline id',
+  proname => 'pg_last_wal_replay_info', prorows => '1',
+  provolatile => 'v', prorettype => 'record', proargtypes => '',
+  proallargtypes => '{pg_lsn,int4}', proargmodes => '{o,o}',
+  proargnames => '{lsn, timeline_id}', prosrc => 'pg_last_wal_replay_info' },
 
 { oid => '3071', descr => 'pause wal replay',
   proname => 'pg_wal_replay_pause', provolatile => 'v', prorettype => 'void',
-- 
2.25.1