From 13e78ef824618f0ee1d05ca887c2bfc1f23b7bd8 Mon Sep 17 00:00:00 2001
From: Yugo Nagata <nagata@sraoss.co.jp>
Date: Tue, 2 Jul 2024 15:12:09 +0900
Subject: [PATCH v2 1/2] Deduplicate codes of LargeObjectExists and
 mvLargeObjectExists

myLargeObjectExists() and LargeObjectExists() share almost same codes
except to whether snapshot can be specified. To deduplicate it,
thie commit renames myLargeObjectExists() to LargeObjectExistsWithSnapshot()
and rewrites LargeObjectExists() to call this internally.
---
 src/backend/catalog/pg_largeobject.c       | 13 +++++--
 src/backend/storage/large_object/inv_api.c | 40 +---------------------
 src/include/catalog/pg_largeobject.h       |  2 ++
 3 files changed, 13 insertions(+), 42 deletions(-)

diff --git a/src/backend/catalog/pg_largeobject.c b/src/backend/catalog/pg_largeobject.c
index e235f7c5e6..5d9fdfbd4c 100644
--- a/src/backend/catalog/pg_largeobject.c
+++ b/src/backend/catalog/pg_largeobject.c
@@ -14,8 +14,6 @@
  */
 #include "postgres.h"
 
-#include "access/genam.h"
-#include "access/htup_details.h"
 #include "access/table.h"
 #include "catalog/catalog.h"
 #include "catalog/indexing.h"
@@ -153,6 +151,15 @@ LargeObjectDrop(Oid loid)
  */
 bool
 LargeObjectExists(Oid loid)
+{
+	return LargeObjectExistsWithSnapshot(loid, NULL);
+}
+
+/*
+ * Same as LargeObjectExists(), except snapshot to read with can be specified.
+ */
+bool
+LargeObjectExistsWithSnapshot(Oid loid, Snapshot snapshot)
 {
 	Relation	pg_lo_meta;
 	ScanKeyData skey[1];
@@ -170,7 +177,7 @@ LargeObjectExists(Oid loid)
 
 	sd = systable_beginscan(pg_lo_meta,
 							LargeObjectMetadataOidIndexId, true,
-							NULL, 1, skey);
+							snapshot, 1, skey);
 
 	tuple = systable_getnext(sd);
 	if (HeapTupleIsValid(tuple))
diff --git a/src/backend/storage/large_object/inv_api.c b/src/backend/storage/large_object/inv_api.c
index f951083324..afce51c167 100644
--- a/src/backend/storage/large_object/inv_api.c
+++ b/src/backend/storage/large_object/inv_api.c
@@ -41,7 +41,6 @@
 #include "catalog/indexing.h"
 #include "catalog/objectaccess.h"
 #include "catalog/pg_largeobject.h"
-#include "catalog/pg_largeobject_metadata.h"
 #include "libpq/libpq-fs.h"
 #include "miscadmin.h"
 #include "storage/large_object.h"
@@ -123,43 +122,6 @@ close_lo_relation(bool isCommit)
 }
 
 
-/*
- * Same as pg_largeobject.c's LargeObjectExists(), except snapshot to
- * read with can be specified.
- */
-static bool
-myLargeObjectExists(Oid loid, Snapshot snapshot)
-{
-	Relation	pg_lo_meta;
-	ScanKeyData skey[1];
-	SysScanDesc sd;
-	HeapTuple	tuple;
-	bool		retval = false;
-
-	ScanKeyInit(&skey[0],
-				Anum_pg_largeobject_metadata_oid,
-				BTEqualStrategyNumber, F_OIDEQ,
-				ObjectIdGetDatum(loid));
-
-	pg_lo_meta = table_open(LargeObjectMetadataRelationId,
-							AccessShareLock);
-
-	sd = systable_beginscan(pg_lo_meta,
-							LargeObjectMetadataOidIndexId, true,
-							snapshot, 1, skey);
-
-	tuple = systable_getnext(sd);
-	if (HeapTupleIsValid(tuple))
-		retval = true;
-
-	systable_endscan(sd);
-
-	table_close(pg_lo_meta, AccessShareLock);
-
-	return retval;
-}
-
-
 /*
  * Extract data field from a pg_largeobject tuple, detoasting if needed
  * and verifying that the length is sane.  Returns data pointer (a bytea *),
@@ -279,7 +241,7 @@ inv_open(Oid lobjId, int flags, MemoryContext mcxt)
 		snapshot = GetActiveSnapshot();
 
 	/* Can't use LargeObjectExists here because we need to specify snapshot */
-	if (!myLargeObjectExists(lobjId, snapshot))
+	if (!LargeObjectExistsWithSnapshot(lobjId, snapshot))
 		ereport(ERROR,
 				(errcode(ERRCODE_UNDEFINED_OBJECT),
 				 errmsg("large object %u does not exist", lobjId)));
diff --git a/src/include/catalog/pg_largeobject.h b/src/include/catalog/pg_largeobject.h
index b40c90b749..e684c58ca9 100644
--- a/src/include/catalog/pg_largeobject.h
+++ b/src/include/catalog/pg_largeobject.h
@@ -20,6 +20,7 @@
 
 #include "catalog/genbki.h"
 #include "catalog/pg_largeobject_d.h"
+#include "utils/snapshot.h"
 
 /* ----------------
  *		pg_largeobject definition.  cpp turns this into
@@ -49,5 +50,6 @@ DECLARE_UNIQUE_INDEX_PKEY(pg_largeobject_loid_pn_index, 2683, LargeObjectLOidPNI
 extern Oid	LargeObjectCreate(Oid loid);
 extern void LargeObjectDrop(Oid loid);
 extern bool LargeObjectExists(Oid loid);
+extern bool LargeObjectExistsWithSnapshot(Oid loid, Snapshot snapshot);
 
 #endif							/* PG_LARGEOBJECT_H */
-- 
2.34.1