Some hacks for replica primotion

pgxn/neon/walproposer.c

@@ -1379,7 +1379,12 @@ ProcessPropStartPos(WalProposer *wp)
 	 * we must bail out, as clog and other non rel data is inconsistent.
 	 */
 	walprop_shared = wp->api.get_shmem_state(wp);
-	if (!wp->config->syncSafekeepers)
+	if (wp->api.get_shmem_state(wp)->bgw_started)
+	{
+		/* Replica promotion */
+		wp->api.set_redo_start_lsn(wp, wp->propTermStartLsn);
+	}
+	else if (!wp->config->syncSafekeepers)
 	{
 		/*
 		 * Basebackup LSN always points to the beginning of the record (not

pgxn/neon/walproposer.h

@@ -675,6 +675,12 @@ typedef struct walproposer_api
 	 */
 	XLogRecPtr	(*get_redo_start_lsn) (WalProposer *wp);
 
+	/*
+	 * Get a basebackup LSN. Used to cross-validate with the latest available
+	 * LSN on the safekeepers.
+	 */
+	void 		(*set_redo_start_lsn) (WalProposer *wp, XLogRecPtr lsn);
+
 	/*
 	 * Finish sync safekeepers with the given LSN. This function should not
 	 * return and should exit the program.

pgxn/neon/walproposer_pg.c

@@ -2040,6 +2040,14 @@ walprop_pg_get_redo_start_lsn(WalProposer *wp)
 	return GetRedoStartLsn();
 }
 
+static void
+walprop_pg_set_redo_start_lsn(WalProposer *wp, XLogRecPtr lsn)
+{
+#if PG_VERSION_NUM >= 150000
+	SetRedoStartLsn(lsn);
+#endif
+}
+
 static bool
 walprop_pg_strong_random(WalProposer *wp, void *buf, size_t len)
 {
@@ -2095,6 +2103,7 @@ static const walproposer_api walprop_pg = {
 	.wait_event_set = walprop_pg_wait_event_set,
 	.strong_random = walprop_pg_strong_random,
 	.get_redo_start_lsn = walprop_pg_get_redo_start_lsn,
+	.set_redo_start_lsn = walprop_pg_set_redo_start_lsn,
 	.finish_sync_safekeepers = walprop_pg_finish_sync_safekeepers,
 	.process_safekeeper_feedback = walprop_pg_process_safekeeper_feedback,
 	.log_internal = walprop_pg_log_internal,

test_runner/regress/test_replica_promote.py

@@ -5,6 +5,7 @@ This far, only contains a test that we don't break and that the data is persiste
 """
 
 import psycopg2
+import time
 from fixtures.neon_fixtures import Endpoint, NeonEnv, wait_replica_caughtup
 from fixtures.pg_version import PgVersion
 from pytest import raises