From bd093125a4f971da0ee1226c0ef12875ca7df16c Mon Sep 17 00:00:00 2001
From: Dilip Kumar <dilipkumar@localhost.localdomain>
Date: Fri, 24 Sep 2021 18:29:17 +0530
Subject: [PATCH v3 5/6] New interface to lock relation id

Same as LockRelationOid, but instead of rel oid it will take
LockRelId object as an input.  So instead of using MyDatabaseId it
will use the dboid passed in the LockRelId object. So this will
provide an option to lock the relation even if we are not connected
to the database.
---
 src/backend/storage/lmgr/lmgr.c | 28 ++++++++++++++++++++++++++++
 src/include/storage/lmgr.h      |  1 +
 2 files changed, 29 insertions(+)

diff --git a/src/backend/storage/lmgr/lmgr.c b/src/backend/storage/lmgr/lmgr.c
index cdf2266d6d..4a321aa4b2 100644
--- a/src/backend/storage/lmgr/lmgr.c
+++ b/src/backend/storage/lmgr/lmgr.c
@@ -175,6 +175,34 @@ ConditionalLockRelationOid(Oid relid, LOCKMODE lockmode)
 	return true;
 }
 
+/*
+ *		LockRelationId
+ *
+ * Lock, given a LockRelId.  Same as LockRelationOid but take LockRelId as an
+ * input.
+ */
+void
+LockRelationId(LockRelId *relid, LOCKMODE lockmode)
+{
+	LOCKTAG		tag;
+	LOCALLOCK  *locallock;
+	LockAcquireResult res;
+
+	SET_LOCKTAG_RELATION(tag, relid->dbId, relid->relId);
+
+	res = LockAcquireExtended(&tag, lockmode, false, false, true, &locallock);
+
+	/*
+	 * Now that we have the lock, check for invalidation messages; see notes
+	 * in LockRelationOid.
+	 */
+	if (res != LOCKACQUIRE_ALREADY_CLEAR)
+	{
+		AcceptInvalidationMessages();
+		MarkLockClear(locallock);
+	}
+}
+
 /*
  *		UnlockRelationId
  *
diff --git a/src/include/storage/lmgr.h b/src/include/storage/lmgr.h
index b009559229..092ee934b4 100644
--- a/src/include/storage/lmgr.h
+++ b/src/include/storage/lmgr.h
@@ -38,6 +38,7 @@ extern void RelationInitLockInfo(Relation relation);
 
 /* Lock a relation */
 extern void LockRelationOid(Oid relid, LOCKMODE lockmode);
+extern void LockRelationId(LockRelId *relid, LOCKMODE lockmode);
 extern bool ConditionalLockRelationOid(Oid relid, LOCKMODE lockmode);
 extern void UnlockRelationId(LockRelId *relid, LOCKMODE lockmode);
 extern void UnlockRelationOid(Oid relid, LOCKMODE lockmode);
-- 
2.23.0