Increase width of RelFileNumbers from 32 bits to 56 bits.

RelFileNumbers are now assigned using a separate counter, instead of
being assigned from the OID counter. This counter never wraps around:
if all 2^56 possible RelFileNumbers are used, an internal error
occurs. As the cluster is limited to 2^64 total bytes of WAL, this
limitation should not cause a problem in practice.

If the counter were 64 bits wide rather than 56 bits wide, we would
need to increase the width of the BufferTag, which might adversely
impact buffer lookup performance. Also, this lets us use bigint for
pg_class.relfilenode and other places where these values are exposed
at the SQL level without worrying about overflow.

This should remove the need to keep "tombstone" files around until
the next checkpoint when relations are removed. We do that to keep
RelFileNumbers from being recycled, but now that won't happen
anyway. However, this patch doesn't actually change anything in
this area; it just makes it possible for a future patch to do so.

Dilip Kumar, based on an idea from Andres Freund, who also reviewed
some earlier versions of the patch. Further review and some
wordsmithing by me. Also reviewed at various points by Ashutosh
Sharma, Vignesh C, Amul Sul, Álvaro Herrera, and Tom Lane.

Discussion: http://postgr.es/m/CA+Tgmobp7+7kmi4gkq7Y+4AM9fTvL+O1oQ4-5gFTT+6Ng-dQ=g@mail.gmail.com

contrib/pg_buffercache/Makefile

@@ -6,8 +6,8 @@ OBJS = \
 	pg_buffercache_pages.o
 
 EXTENSION = pg_buffercache
-DATA = pg_buffercache--1.2.sql pg_buffercache--1.2--1.3.sql \
+DATA = pg_buffercache--1.0--1.1.sql pg_buffercache--1.1--1.2.sql pg_buffercache--1.2.sql \
-	pg_buffercache--1.1--1.2.sql pg_buffercache--1.0--1.1.sql
+	pg_buffercache--1.2--1.3.sql pg_buffercache--1.3--1.4.sql
 PGFILEDESC = "pg_buffercache - monitoring of shared buffer cache in real-time"
 
 REGRESS = pg_buffercache

contrib/pg_buffercache/pg_buffercache--1.3--1.4.sql

@@ -0,0 +1,30 @@
+/* contrib/pg_buffercache/pg_buffercache--1.3--1.4.sql */
+
+-- complain if script is sourced in psql, rather than via ALTER EXTENSION
+\echo Use "ALTER EXTENSION pg_buffercache UPDATE TO '1.4'" to load this file. \quit
+
+/* First we have to remove them from the extension */
+ALTER EXTENSION pg_buffercache DROP VIEW pg_buffercache;
+ALTER EXTENSION pg_buffercache DROP FUNCTION pg_buffercache_pages();
+
+/* Then we can drop them */
+DROP VIEW pg_buffercache;
+DROP FUNCTION pg_buffercache_pages();
+
+/* Now redefine */
+CREATE FUNCTION pg_buffercache_pages()
+RETURNS SETOF RECORD
+AS 'MODULE_PATHNAME', 'pg_buffercache_pages_v1_4'
+LANGUAGE C PARALLEL SAFE;
+
+CREATE VIEW pg_buffercache AS
+	SELECT P.* FROM pg_buffercache_pages() AS P
+	(bufferid integer, relfilenode int8, reltablespace oid, reldatabase oid,
+	 relforknumber int2, relblocknumber int8, isdirty bool, usagecount int2,
+	 pinning_backends int4);
+
+-- Don't want these to be available to public.
+REVOKE ALL ON FUNCTION pg_buffercache_pages() FROM PUBLIC;
+REVOKE ALL ON pg_buffercache FROM PUBLIC;
+GRANT EXECUTE ON FUNCTION pg_buffercache_pages() TO pg_monitor;
+GRANT SELECT ON pg_buffercache TO pg_monitor;

contrib/pg_buffercache/pg_buffercache.control

@@ -1,5 +1,5 @@
 # pg_buffercache extension
 comment = 'examine the shared buffer cache'
-default_version = '1.3'
+default_version = '1.4'
 module_pathname = '$libdir/pg_buffercache'
 relocatable = true

contrib/pg_buffercache/pg_buffercache_pages.c

@@ -59,9 +59,10 @@ typedef struct
  * relation node/tablespace/database/blocknum and dirty indicator.
  */
 PG_FUNCTION_INFO_V1(pg_buffercache_pages);
+PG_FUNCTION_INFO_V1(pg_buffercache_pages_v1_4);
 
-Datum
+static Datum
-pg_buffercache_pages(PG_FUNCTION_ARGS)
+pg_buffercache_pages_internal(PG_FUNCTION_ARGS, Oid rfn_typid)
 {
 	FuncCallContext *funcctx;
 	Datum		result;
@@ -103,7 +104,7 @@ pg_buffercache_pages(PG_FUNCTION_ARGS)
 		TupleDescInitEntry(tupledesc, (AttrNumber) 1, "bufferid",
 						   INT4OID, -1, 0);
 		TupleDescInitEntry(tupledesc, (AttrNumber) 2, "relfilenode",
-						   OIDOID, -1, 0);
+						   rfn_typid, -1, 0);
 		TupleDescInitEntry(tupledesc, (AttrNumber) 3, "reltablespace",
 						   OIDOID, -1, 0);
 		TupleDescInitEntry(tupledesc, (AttrNumber) 4, "reldatabase",
@@ -209,7 +210,24 @@ pg_buffercache_pages(PG_FUNCTION_ARGS)
 		}
 		else
 		{
-			values[1] = ObjectIdGetDatum(fctx->record[i].relfilenumber);
+			if (rfn_typid == INT8OID)
+				values[1] =
+					Int64GetDatum((int64) fctx->record[i].relfilenumber);
+			else
+			{
+				Assert(rfn_typid == OIDOID);
+
+				if (fctx->record[i].relfilenumber > OID_MAX)
+					ereport(ERROR,
+							errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+							errmsg("relfilenode %llu is too large to be represented as an OID",
+									(unsigned long long) fctx->record[i].relfilenumber),
+							errhint("Upgrade the extension using ALTER EXTENSION pg_buffercache UPDATE"));
+
+				values[1] =
+					ObjectIdGetDatum((Oid) fctx->record[i].relfilenumber);
+			}
+
 			nulls[1] = false;
 			values[2] = ObjectIdGetDatum(fctx->record[i].reltablespace);
 			nulls[2] = false;
@@ -237,3 +255,16 @@ pg_buffercache_pages(PG_FUNCTION_ARGS)
 	else
 		SRF_RETURN_DONE(funcctx);
 }
+
+/* entry point for old extension version */
+Datum
+pg_buffercache_pages(PG_FUNCTION_ARGS)
+{
+	return pg_buffercache_pages_internal(fcinfo, OIDOID);
+}
+
+Datum
+pg_buffercache_pages_v1_4(PG_FUNCTION_ARGS)
+{
+	return pg_buffercache_pages_internal(fcinfo, INT8OID);
+}

contrib/pg_prewarm/autoprewarm.c

@@ -345,7 +345,7 @@ apw_load_buffers(void)
 	{
 		unsigned	forknum;
 
-		if (fscanf(file, "%u,%u,%u,%u,%u\n", &blkinfo[i].database,
+		if (fscanf(file, "%u,%u," UINT64_FORMAT ",%u,%u\n", &blkinfo[i].database,
 				   &blkinfo[i].tablespace, &blkinfo[i].filenumber,
 				   &forknum, &blkinfo[i].blocknum) != 5)
 			ereport(ERROR,
@@ -669,7 +669,7 @@ apw_dump_now(bool is_bgworker, bool dump_unlogged)
 	{
 		CHECK_FOR_INTERRUPTS();
 
-		ret = fprintf(file, "%u,%u,%u,%u,%u\n",
+		ret = fprintf(file, "%u,%u," UINT64_FORMAT ",%u,%u\n",
 					  block_info_array[i].database,
 					  block_info_array[i].tablespace,
 					  block_info_array[i].filenumber,

contrib/pg_walinspect/expected/pg_walinspect.out

@@ -54,9 +54,9 @@ SELECT COUNT(*) >= 0 AS ok FROM pg_get_wal_stats_till_end_of_wal(:'wal_lsn1');
 -- ===================================================================
 -- Test for filtering out WAL records of a particular table
 -- ===================================================================
-SELECT oid AS sample_tbl_oid FROM pg_class WHERE relname = 'sample_tbl' \gset
+SELECT relfilenode AS sample_tbl_relfilenode FROM pg_class WHERE relname = 'sample_tbl' \gset
 SELECT COUNT(*) >= 1 AS ok FROM pg_get_wal_records_info(:'wal_lsn1', :'wal_lsn2')
-			WHERE block_ref LIKE concat('%', :'sample_tbl_oid', '%') AND resource_manager = 'Heap';
+			WHERE block_ref LIKE concat('%', :'sample_tbl_relfilenode', '%') AND resource_manager = 'Heap';
  ok 
 ----
  t

contrib/pg_walinspect/sql/pg_walinspect.sql

@@ -39,10 +39,10 @@ SELECT COUNT(*) >= 0 AS ok FROM pg_get_wal_stats_till_end_of_wal(:'wal_lsn1');
 -- Test for filtering out WAL records of a particular table
 -- ===================================================================
 
-SELECT oid AS sample_tbl_oid FROM pg_class WHERE relname = 'sample_tbl' \gset
+SELECT relfilenode AS sample_tbl_relfilenode FROM pg_class WHERE relname = 'sample_tbl' \gset
 
 SELECT COUNT(*) >= 1 AS ok FROM pg_get_wal_records_info(:'wal_lsn1', :'wal_lsn2')
-			WHERE block_ref LIKE concat('%', :'sample_tbl_oid', '%') AND resource_manager = 'Heap';
+			WHERE block_ref LIKE concat('%', :'sample_tbl_relfilenode', '%') AND resource_manager = 'Heap';
 
 -- ===================================================================
 -- Test for filtering out WAL records based on resource_manager and

doc/src/sgml/catalogs.sgml

@@ -1984,7 +1984,7 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>relfilenode</structfield> <type>oid</type>
+       <structfield>relfilenode</structfield> <type>int8</type>
       </para>
       <para>
        Name of the on-disk file of this relation; zero means this

doc/src/sgml/func.sgml

@@ -25210,6 +25210,11 @@ SELECT collation for ('foo' COLLATE "de_DE");
        <entry><type>timestamp with time zone</type></entry>
       </row>
 
+      <row>
+       <entry><structfield>next_relfilenumber</structfield></entry>
+       <entry><type>timestamp with time zone</type></entry>
+      </row>
+
      </tbody>
     </tgroup>
    </table>

doc/src/sgml/pgbuffercache.sgml

@@ -62,7 +62,7 @@
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>relfilenode</structfield> <type>oid</type>
+       <structfield>relfilenode</structfield> <type>int8</type>
        (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>relfilenode</structfield>)
       </para>
       <para>

doc/src/sgml/storage.sgml

@@ -217,11 +217,12 @@ with the suffix <literal>_init</literal> (see <xref linkend="storage-init"/>).
 
 <caution>
 <para>
-Note that while a table's filenode often matches its OID, this is
+Note that a table's filenode will normally be different than the OID. For
-<emphasis>not</emphasis> necessarily the case; some operations, like
+system tables, the initial filenode will be equal to the table OID, but it will
-<command>TRUNCATE</command>, <command>REINDEX</command>, <command>CLUSTER</command> and some forms
+be different if the table has ever been subjected to a rewriting operation,
-of <command>ALTER TABLE</command>, can change the filenode while preserving the OID.
+such as <command>TRUNCATE</command>, <command>REINDEX</command>,
-Avoid assuming that filenode and table OID are the same.
+<command>CLUSTER</command> or some forms of <command>ALTER TABLE</command>.
+For user tables, even the initial filenode will be different than the table OID.
 Also, for certain system catalogs including <structname>pg_class</structname> itself,
 <structname>pg_class</structname>.<structfield>relfilenode</structfield> contains zero.  The
 actual filenode number of these catalogs is stored in a lower-level data

src/backend/access/gin/ginxlog.c

@@ -100,7 +100,7 @@ ginRedoInsertEntry(Buffer buffer, bool isLeaf, BlockNumber rightblkno, void *rda
 		BlockNumber blknum;
 
 		BufferGetTag(buffer, &locator, &forknum, &blknum);
-		elog(ERROR, "failed to add item to index page in %u/%u/%u",
+		elog(ERROR, "failed to add item to index page in %u/%u/" UINT64_FORMAT,
 			 locator.spcOid, locator.dbOid, locator.relNumber);
 	}
 }

src/backend/access/rmgrdesc/gistdesc.c

@@ -26,7 +26,7 @@ out_gistxlogPageUpdate(StringInfo buf, gistxlogPageUpdate *xlrec)
 static void
 out_gistxlogPageReuse(StringInfo buf, gistxlogPageReuse *xlrec)
 {
-	appendStringInfo(buf, "rel %u/%u/%u; blk %u; latestRemovedXid %u:%u",
+	appendStringInfo(buf, "rel %u/%u/" UINT64_FORMAT "; blk %u; latestRemovedXid %u:%u",
 					 xlrec->locator.spcOid, xlrec->locator.dbOid,
 					 xlrec->locator.relNumber, xlrec->block,
 					 EpochFromFullTransactionId(xlrec->latestRemovedFullXid),

src/backend/access/rmgrdesc/heapdesc.c

@@ -169,7 +169,7 @@ heap2_desc(StringInfo buf, XLogReaderState *record)
 	{
 		xl_heap_new_cid *xlrec = (xl_heap_new_cid *) rec;
 
-		appendStringInfo(buf, "rel %u/%u/%u; tid %u/%u",
+		appendStringInfo(buf, "rel %u/%u/" UINT64_FORMAT "; tid %u/%u",
 						 xlrec->target_locator.spcOid,
 						 xlrec->target_locator.dbOid,
 						 xlrec->target_locator.relNumber,

src/backend/access/rmgrdesc/nbtdesc.c

@@ -100,7 +100,7 @@ btree_desc(StringInfo buf, XLogReaderState *record)
 			{
 				xl_btree_reuse_page *xlrec = (xl_btree_reuse_page *) rec;
 
-				appendStringInfo(buf, "rel %u/%u/%u; latestRemovedXid %u:%u",
+				appendStringInfo(buf, "rel %u/%u/" UINT64_FORMAT "; latestRemovedXid %u:%u",
 								 xlrec->locator.spcOid, xlrec->locator.dbOid,
 								 xlrec->locator.relNumber,
 								 EpochFromFullTransactionId(xlrec->latestRemovedFullXid),

src/backend/access/rmgrdesc/seqdesc.c

@@ -25,7 +25,7 @@ seq_desc(StringInfo buf, XLogReaderState *record)
 	xl_seq_rec *xlrec = (xl_seq_rec *) rec;
 
 	if (info == XLOG_SEQ_LOG)
-		appendStringInfo(buf, "rel %u/%u/%u",
+		appendStringInfo(buf, "rel %u/%u/" UINT64_FORMAT,
 						 xlrec->locator.spcOid, xlrec->locator.dbOid,
 						 xlrec->locator.relNumber);
 }

src/backend/access/rmgrdesc/xlogdesc.c

@@ -45,8 +45,8 @@ xlog_desc(StringInfo buf, XLogReaderState *record)
 		CheckPoint *checkpoint = (CheckPoint *) rec;
 
 		appendStringInfo(buf, "redo %X/%X; "
-						 "tli %u; prev tli %u; fpw %s; xid %u:%u; oid %u; multi %u; offset %u; "
+						 "tli %u; prev tli %u; fpw %s; xid %u:%u; relfilenumber " UINT64_FORMAT ";oid %u; "
-						 "oldest xid %u in DB %u; oldest multi %u in DB %u; "
+						 "multi %u; offset %u; oldest xid %u in DB %u; oldest multi %u in DB %u; "
 						 "oldest/newest commit timestamp xid: %u/%u; "
 						 "oldest running xid %u; %s",
 						 LSN_FORMAT_ARGS(checkpoint->redo),
@@ -55,6 +55,7 @@ xlog_desc(StringInfo buf, XLogReaderState *record)
 						 checkpoint->fullPageWrites ? "true" : "false",
 						 EpochFromFullTransactionId(checkpoint->nextXid),
 						 XidFromFullTransactionId(checkpoint->nextXid),
+						 checkpoint->nextRelFileNumber,
 						 checkpoint->nextOid,
 						 checkpoint->nextMulti,
 						 checkpoint->nextMultiOffset,
@@ -74,6 +75,13 @@ xlog_desc(StringInfo buf, XLogReaderState *record)
 		memcpy(&nextOid, rec, sizeof(Oid));
 		appendStringInfo(buf, "%u", nextOid);
 	}
+	else if (info == XLOG_NEXT_RELFILENUMBER)
+	{
+		RelFileNumber nextRelFileNumber;
+
+		memcpy(&nextRelFileNumber, rec, sizeof(RelFileNumber));
+		appendStringInfo(buf, UINT64_FORMAT, nextRelFileNumber);
+	}
 	else if (info == XLOG_RESTORE_POINT)
 	{
 		xl_restore_point *xlrec = (xl_restore_point *) rec;
@@ -169,6 +177,9 @@ xlog_identify(uint8 info)
 		case XLOG_NEXTOID:
 			id = "NEXTOID";
 			break;
+		case XLOG_NEXT_RELFILENUMBER:
+			id = "NEXT_RELFILENUMBER";
+			break;
 		case XLOG_SWITCH:
 			id = "SWITCH";
 			break;
@@ -237,7 +248,7 @@ XLogRecGetBlockRefInfo(XLogReaderState *record, bool pretty,
 				appendStringInfoChar(buf, ' ');
 
 			appendStringInfo(buf,
-							 "blkref #%d: rel %u/%u/%u fork %s blk %u",
+							 "blkref #%d: rel %u/%u/" UINT64_FORMAT " fork %s blk %u",
 							 block_id,
 							 rlocator.spcOid, rlocator.dbOid, rlocator.relNumber,
 							 forkNames[forknum],
@@ -297,7 +308,7 @@ XLogRecGetBlockRefInfo(XLogReaderState *record, bool pretty,
 			if (forknum != MAIN_FORKNUM)
 			{
 				appendStringInfo(buf,
-								 ", blkref #%d: rel %u/%u/%u fork %s blk %u",
+								 ", blkref #%d: rel %u/%u/" UINT64_FORMAT " fork %s blk %u",
 								 block_id,
 								 rlocator.spcOid, rlocator.dbOid, rlocator.relNumber,
 								 forkNames[forknum],
@@ -306,7 +317,7 @@ XLogRecGetBlockRefInfo(XLogReaderState *record, bool pretty,
 			else
 			{
 				appendStringInfo(buf,
-								 ", blkref #%d: rel %u/%u/%u blk %u",
+								 ", blkref #%d: rel %u/%u/" UINT64_FORMAT " blk %u",
 								 block_id,
 								 rlocator.spcOid, rlocator.dbOid, rlocator.relNumber,
 								 blk);

src/backend/access/transam/README

@@ -692,8 +692,9 @@ by having database restart search for files that don't have any committed
 entry in pg_class, but that currently isn't done because of the possibility
 of deleting data that is useful for forensic analysis of the crash.
 Orphan files are harmless --- at worst they waste a bit of disk space ---
-because we check for on-disk collisions when allocating new relfilenumber
+because the relfilenumber counter is monotonically increasing.  The maximum
-OIDs.  So cleaning up isn't really necessary.
+value is 2^56-1, and there is no provision for wraparound.  Thus, on-disk
+collisions aren't possible.
 
 3. Deleting a table, which requires an unlink() that could fail.
 

src/backend/access/transam/varsup.c

@@ -13,12 +13,16 @@
 
 #include "postgres.h"
 
+#include <unistd.h>
+
 #include "access/clog.h"
 #include "access/commit_ts.h"
 #include "access/subtrans.h"
 #include "access/transam.h"
 #include "access/xact.h"
 #include "access/xlogutils.h"
+#include "catalog/pg_class.h"
+#include "catalog/pg_tablespace.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
 #include "postmaster/autovacuum.h"
@@ -30,6 +34,15 @@
 /* Number of OIDs to prefetch (preallocate) per XLOG write */
 #define VAR_OID_PREFETCH		8192
 
+/* Number of RelFileNumbers to be logged per XLOG write */
+#define VAR_RELNUMBER_PER_XLOG				512
+
+/*
+ * Need to log more if remaining logged RelFileNumbers are less than the
+ * threshold.  Valid range could be between 0 to VAR_RELNUMBER_PER_XLOG - 1.
+ */
+#define VAR_RELNUMBER_NEW_XLOG_THRESHOLD	256
+
 /* pointer to "variable cache" in shared memory (set up by shmem.c) */
 VariableCache ShmemVariableCache = NULL;
 
@@ -521,8 +534,7 @@ ForceTransactionIdLimitUpdate(void)
  * wide, counter wraparound will occur eventually, and therefore it is unwise
  * to assume they are unique unless precautions are taken to make them so.
  * Hence, this routine should generally not be used directly.  The only direct
- * callers should be GetNewOidWithIndex() and GetNewRelFileNumber() in
+ * caller should be GetNewOidWithIndex() in catalog/catalog.c.
- * catalog/catalog.c.
  */
 Oid
 GetNewObjectId(void)
@@ -612,6 +624,199 @@ SetNextObjectId(Oid nextOid)
 	LWLockRelease(OidGenLock);
 }
 
+/*
+ * GetNewRelFileNumber
+ *
+ * Similar to GetNewObjectId but instead of new Oid it generates new
+ * relfilenumber.
+ */
+RelFileNumber
+GetNewRelFileNumber(Oid reltablespace, char relpersistence)
+{
+	RelFileNumber result;
+	RelFileNumber nextRelFileNumber,
+				  loggedRelFileNumber,
+				  flushedRelFileNumber;
+
+	StaticAssertStmt(VAR_RELNUMBER_NEW_XLOG_THRESHOLD < VAR_RELNUMBER_PER_XLOG,
+					 "VAR_RELNUMBER_NEW_XLOG_THRESHOLD must be smaller than VAR_RELNUMBER_PER_XLOG");
+
+	/* safety check, we should never get this far in a HS standby */
+	if (RecoveryInProgress())
+		elog(ERROR, "cannot assign RelFileNumber during recovery");
+
+	if (IsBinaryUpgrade)
+		elog(ERROR, "cannot assign RelFileNumber during binary upgrade");
+
+	LWLockAcquire(RelFileNumberGenLock, LW_EXCLUSIVE);
+
+	nextRelFileNumber = ShmemVariableCache->nextRelFileNumber;
+	loggedRelFileNumber = ShmemVariableCache->loggedRelFileNumber;
+	flushedRelFileNumber = ShmemVariableCache->flushedRelFileNumber;
+
+	Assert(nextRelFileNumber <= flushedRelFileNumber);
+	Assert(flushedRelFileNumber <= loggedRelFileNumber);
+
+	/* check for the wraparound for the relfilenumber counter */
+	if (unlikely(nextRelFileNumber > MAX_RELFILENUMBER))
+		elog(ERROR, "relfilenumber is too large");
+
+	/*
+	 * If the remaining logged relfilenumbers values are less than the
+	 * threshold value then log more.  Ideally, we can wait until all
+	 * relfilenumbers have been consumed before logging more.  Nevertheless, if
+	 * we do that, we must immediately flush the logged wal record because we
+	 * want to ensure that the nextRelFileNumber is always larger than any
+	 * relfilenumber already in use on disk.  And, to maintain that invariant,
+	 * we must make sure that the record we log reaches the disk before any new
+	 * files are created with the newly logged range.
+	 *
+	 * So in order to avoid flushing the wal immediately, we always log before
+	 * consuming all the relfilenumber, and now we only have to flush the newly
+	 * logged relfilenumber wal before consuming the relfilenumber from this
+	 * new range.  By the time we need to flush this wal, hopefully, those have
+	 * already been flushed with some other XLogFlush operation.
+	 */
+	if (loggedRelFileNumber - nextRelFileNumber <=
+		VAR_RELNUMBER_NEW_XLOG_THRESHOLD)
+	{
+		XLogRecPtr	recptr;
+
+		loggedRelFileNumber = loggedRelFileNumber + VAR_RELNUMBER_PER_XLOG;
+		recptr = LogNextRelFileNumber(loggedRelFileNumber);
+		ShmemVariableCache->loggedRelFileNumber = loggedRelFileNumber;
+
+		/* remember for the future flush */
+		ShmemVariableCache->loggedRelFileNumberRecPtr = recptr;
+	}
+
+	/*
+	 * If the nextRelFileNumber is already reached to the already flushed
+	 * relfilenumber then flush the WAL for previously logged relfilenumber.
+	 */
+	if (nextRelFileNumber >= flushedRelFileNumber)
+	{
+		XLogFlush(ShmemVariableCache->loggedRelFileNumberRecPtr);
+		ShmemVariableCache->flushedRelFileNumber = loggedRelFileNumber;
+	}
+
+	result = ShmemVariableCache->nextRelFileNumber;
+
+	/* we should never be using any relfilenumber outside the flushed range */
+	Assert(result <= ShmemVariableCache->flushedRelFileNumber);
+
+	(ShmemVariableCache->nextRelFileNumber)++;
+
+	LWLockRelease(RelFileNumberGenLock);
+
+	/*
+	 * Because the RelFileNumber counter only ever increases and never wraps
+	 * around, it should be impossible for the newly-allocated RelFileNumber to
+	 * already be in use.  But, if Asserts are enabled, double check that
+	 * there's no main-fork relation file with the new RelFileNumber already on
+	 * disk.
+	 */
+#ifdef USE_ASSERT_CHECKING
+	{
+		RelFileLocatorBackend rlocator;
+		char	   *rpath;
+		BackendId	backend;
+
+		switch (relpersistence)
+		{
+			case RELPERSISTENCE_TEMP:
+				backend = BackendIdForTempRelations();
+				break;
+			case RELPERSISTENCE_UNLOGGED:
+			case RELPERSISTENCE_PERMANENT:
+				backend = InvalidBackendId;
+				break;
+			default:
+				elog(ERROR, "invalid relpersistence: %c", relpersistence);
+		}
+
+		/* this logic should match RelationInitPhysicalAddr */
+		rlocator.locator.spcOid =
+			reltablespace ? reltablespace : MyDatabaseTableSpace;
+		rlocator.locator.dbOid = (reltablespace == GLOBALTABLESPACE_OID) ?
+			InvalidOid : MyDatabaseId;
+		rlocator.locator.relNumber = result;
+
+		/*
+		 * The relpath will vary based on the backend ID, so we must
+		 * initialize that properly here to make sure that any collisions
+		 * based on filename are properly detected.
+		 */
+		rlocator.backend = backend;
+
+		/* check for existing file of same name. */
+		rpath = relpath(rlocator, MAIN_FORKNUM);
+		Assert(access(rpath, F_OK) != 0);
+	}
+#endif
+
+	return result;
+}
+
+/*
+ * SetNextRelFileNumber
+ *
+ * This may only be called during pg_upgrade; it advances the RelFileNumber
+ * counter to the specified value if the current value is smaller than the
+ * input value.
+ */
+void
+SetNextRelFileNumber(RelFileNumber relnumber)
+{
+	/* safety check, we should never get this far in a HS standby */
+	if (RecoveryInProgress())
+		elog(ERROR, "cannot set RelFileNumber during recovery");
+
+	if (!IsBinaryUpgrade)
+		elog(ERROR, "RelFileNumber can be set only during binary upgrade");
+
+	LWLockAcquire(RelFileNumberGenLock, LW_EXCLUSIVE);
+
+	/*
+	 * If previous assigned value of the nextRelFileNumber is already higher
+	 * than the current value then nothing to be done.  This is possible
+	 * because during upgrade the objects are not created in relfilenumber
+	 * order.
+	 */
+	if (relnumber <= ShmemVariableCache->nextRelFileNumber)
+	{
+		LWLockRelease(RelFileNumberGenLock);
+		return;
+	}
+
+	/*
+	 * If the new relfilenumber to be set is greater than or equal to already
+	 * flushed relfilenumber then log more and flush immediately.
+	 *
+	 * (This is less efficient than GetNewRelFileNumber, which arranges to
+	 * log some new relfilenumbers before the old batch is exhausted in the
+	 * hope that a flush will happen in the background before any values are
+	 * needed from the new batch. However, since thais is only used during
+	 * binary upgrade, it shouldn't really matter.)
+	 */
+	if (relnumber >= ShmemVariableCache->flushedRelFileNumber)
+	{
+		RelFileNumber newlogrelnum;
+
+		newlogrelnum = relnumber + VAR_RELNUMBER_PER_XLOG;
+		XLogFlush(LogNextRelFileNumber(newlogrelnum));
+
+		/* we have flushed whatever we have logged so no pending flush */
+		ShmemVariableCache->loggedRelFileNumber = newlogrelnum;
+		ShmemVariableCache->flushedRelFileNumber = newlogrelnum;
+		ShmemVariableCache->loggedRelFileNumberRecPtr = InvalidXLogRecPtr;
+	}
+
+	ShmemVariableCache->nextRelFileNumber = relnumber;
+
+	LWLockRelease(RelFileNumberGenLock);
+}
+
 /*
  * StopGeneratingPinnedObjectIds
  *

src/backend/access/transam/xlog.c

@@ -4712,6 +4712,7 @@ BootStrapXLOG(void)
 	checkPoint.nextXid =
 		FullTransactionIdFromEpochAndXid(0, FirstNormalTransactionId);
 	checkPoint.nextOid = FirstGenbkiObjectId;
+	checkPoint.nextRelFileNumber = FirstNormalRelFileNumber;
 	checkPoint.nextMulti = FirstMultiXactId;
 	checkPoint.nextMultiOffset = 0;
 	checkPoint.oldestXid = FirstNormalTransactionId;
@@ -4725,7 +4726,11 @@ BootStrapXLOG(void)
 
 	ShmemVariableCache->nextXid = checkPoint.nextXid;
 	ShmemVariableCache->nextOid = checkPoint.nextOid;
+	ShmemVariableCache->nextRelFileNumber = checkPoint.nextRelFileNumber;
 	ShmemVariableCache->oidCount = 0;
+	ShmemVariableCache->loggedRelFileNumber = checkPoint.nextRelFileNumber;
+	ShmemVariableCache->flushedRelFileNumber = checkPoint.nextRelFileNumber;
+	ShmemVariableCache->loggedRelFileNumberRecPtr = InvalidXLogRecPtr;
 	MultiXactSetNextMXact(checkPoint.nextMulti, checkPoint.nextMultiOffset);
 	AdvanceOldestClogXid(checkPoint.oldestXid);
 	SetTransactionIdLimit(checkPoint.oldestXid, checkPoint.oldestXidDB);
@@ -5191,7 +5196,10 @@ StartupXLOG(void)
 	/* initialize shared memory variables from the checkpoint record */
 	ShmemVariableCache->nextXid = checkPoint.nextXid;
 	ShmemVariableCache->nextOid = checkPoint.nextOid;
+	ShmemVariableCache->nextRelFileNumber = checkPoint.nextRelFileNumber;
 	ShmemVariableCache->oidCount = 0;
+	ShmemVariableCache->loggedRelFileNumber = checkPoint.nextRelFileNumber;
+	ShmemVariableCache->flushedRelFileNumber = checkPoint.nextRelFileNumber;
 	MultiXactSetNextMXact(checkPoint.nextMulti, checkPoint.nextMultiOffset);
 	AdvanceOldestClogXid(checkPoint.oldestXid);
 	SetTransactionIdLimit(checkPoint.oldestXid, checkPoint.oldestXidDB);
@@ -6663,6 +6671,24 @@ CreateCheckPoint(int flags)
 		checkPoint.nextOid += ShmemVariableCache->oidCount;
 	LWLockRelease(OidGenLock);
 
+	/*
+	 * If this is a shutdown checkpoint then we can safely start allocating
+	 * relfilenumber from the nextRelFileNumber value after the restart because
+	 * no one one else can use the relfilenumber beyond that number before the
+	 * shutdown.  OTOH, if it is a normal checkpoint then if there is a crash
+	 * after this point then we might end up reusing the same relfilenumbers
+	 * after the restart so we need to set the nextRelFileNumber to the already
+	 * logged relfilenumber as no one will use number beyond this limit without
+	 * logging again.
+	 */
+	LWLockAcquire(RelFileNumberGenLock, LW_SHARED);
+	if (shutdown)
+		checkPoint.nextRelFileNumber = ShmemVariableCache->nextRelFileNumber;
+	else
+		checkPoint.nextRelFileNumber = ShmemVariableCache->loggedRelFileNumber;
+
+	LWLockRelease(RelFileNumberGenLock);
+
 	MultiXactGetCheckptMulti(shutdown,
 							 &checkPoint.nextMulti,
 							 &checkPoint.nextMultiOffset,
@@ -7540,6 +7566,24 @@ XLogPutNextOid(Oid nextOid)
 	 */
 }
 
+/*
+ * Similar to the XLogPutNextOid but instead of writing NEXTOID log record it
+ * writes a NEXT_RELFILENUMBER log record.  It also returns the XLogRecPtr of
+ * the currently logged relfilenumber record, so that the caller can flush it
+ * at the appropriate time.
+ */
+XLogRecPtr
+LogNextRelFileNumber(RelFileNumber nextrelnumber)
+{
+	XLogRecPtr	recptr;
+
+	XLogBeginInsert();
+	XLogRegisterData((char *) (&nextrelnumber), sizeof(RelFileNumber));
+	recptr = XLogInsert(RM_XLOG_ID, XLOG_NEXT_RELFILENUMBER);
+
+	return recptr;
+}
+
 /*
  * Write an XLOG SWITCH record.
  *
@@ -7755,6 +7799,17 @@ xlog_redo(XLogReaderState *record)
 		ShmemVariableCache->oidCount = 0;
 		LWLockRelease(OidGenLock);
 	}
+	if (info == XLOG_NEXT_RELFILENUMBER)
+	{
+		RelFileNumber nextRelFileNumber;
+
+		memcpy(&nextRelFileNumber, XLogRecGetData(record), sizeof(RelFileNumber));
+		LWLockAcquire(RelFileNumberGenLock, LW_EXCLUSIVE);
+		ShmemVariableCache->nextRelFileNumber = nextRelFileNumber;
+		ShmemVariableCache->loggedRelFileNumber = nextRelFileNumber;
+		ShmemVariableCache->flushedRelFileNumber = nextRelFileNumber;
+		LWLockRelease(RelFileNumberGenLock);
+	}
 	else if (info == XLOG_CHECKPOINT_SHUTDOWN)
 	{
 		CheckPoint	checkPoint;
@@ -7769,6 +7824,11 @@ xlog_redo(XLogReaderState *record)
 		ShmemVariableCache->nextOid = checkPoint.nextOid;
 		ShmemVariableCache->oidCount = 0;
 		LWLockRelease(OidGenLock);
+		LWLockAcquire(RelFileNumberGenLock, LW_EXCLUSIVE);
+		ShmemVariableCache->nextRelFileNumber = checkPoint.nextRelFileNumber;
+		ShmemVariableCache->loggedRelFileNumber = checkPoint.nextRelFileNumber;
+		ShmemVariableCache->flushedRelFileNumber = checkPoint.nextRelFileNumber;
+		LWLockRelease(RelFileNumberGenLock);
 		MultiXactSetNextMXact(checkPoint.nextMulti,
 							  checkPoint.nextMultiOffset);
 

src/backend/access/transam/xlogprefetcher.c

@@ -613,7 +613,7 @@ XLogPrefetcherNextBlock(uintptr_t pgsr_private, XLogRecPtr *lsn)
 
 #ifdef XLOGPREFETCHER_DEBUG_LEVEL
 						elog(XLOGPREFETCHER_DEBUG_LEVEL,
-							 "suppressing prefetch in relation %u/%u/%u until %X/%X is replayed, which creates the relation",
+							 "suppressing prefetch in relation %u/%u/" UINT64_FORMAT " until %X/%X is replayed, which creates the relation",
 							 xlrec->rlocator.spcOid,
 							 xlrec->rlocator.dbOid,
 							 xlrec->rlocator.relNumber,
@@ -636,7 +636,7 @@ XLogPrefetcherNextBlock(uintptr_t pgsr_private, XLogRecPtr *lsn)
 
 #ifdef XLOGPREFETCHER_DEBUG_LEVEL
 					elog(XLOGPREFETCHER_DEBUG_LEVEL,
-						 "suppressing prefetch in relation %u/%u/%u from block %u until %X/%X is replayed, which truncates the relation",
+						 "suppressing prefetch in relation %u/%u/" UINT64_FORMAT " from block %u until %X/%X is replayed, which truncates the relation",
 						 xlrec->rlocator.spcOid,
 						 xlrec->rlocator.dbOid,
 						 xlrec->rlocator.relNumber,
@@ -735,7 +735,7 @@ XLogPrefetcherNextBlock(uintptr_t pgsr_private, XLogRecPtr *lsn)
 			{
 #ifdef XLOGPREFETCHER_DEBUG_LEVEL
 				elog(XLOGPREFETCHER_DEBUG_LEVEL,
-					 "suppressing all prefetch in relation %u/%u/%u until %X/%X is replayed, because the relation does not exist on disk",
+					 "suppressing all prefetch in relation %u/%u/" UINT64_FORMAT " until %X/%X is replayed, because the relation does not exist on disk",
 					 reln->smgr_rlocator.locator.spcOid,
 					 reln->smgr_rlocator.locator.dbOid,
 					 reln->smgr_rlocator.locator.relNumber,
@@ -756,7 +756,7 @@ XLogPrefetcherNextBlock(uintptr_t pgsr_private, XLogRecPtr *lsn)
 			{
 #ifdef XLOGPREFETCHER_DEBUG_LEVEL
 				elog(XLOGPREFETCHER_DEBUG_LEVEL,
-					 "suppressing prefetch in relation %u/%u/%u from block %u until %X/%X is replayed, because the relation is too small",
+					 "suppressing prefetch in relation %u/%u/" UINT64_FORMAT " from block %u until %X/%X is replayed, because the relation is too small",
 					 reln->smgr_rlocator.locator.spcOid,
 					 reln->smgr_rlocator.locator.dbOid,
 					 reln->smgr_rlocator.locator.relNumber,
@@ -795,7 +795,7 @@ XLogPrefetcherNextBlock(uintptr_t pgsr_private, XLogRecPtr *lsn)
 				 * truncated beneath our feet?
 				 */
 				elog(ERROR,
-					 "could not prefetch relation %u/%u/%u block %u",
+					 "could not prefetch relation %u/%u/" UINT64_FORMAT " block %u",
 					 reln->smgr_rlocator.locator.spcOid,
 					 reln->smgr_rlocator.locator.dbOid,
 					 reln->smgr_rlocator.locator.relNumber,
@@ -934,7 +934,7 @@ XLogPrefetcherIsFiltered(XLogPrefetcher *prefetcher, RelFileLocator rlocator,
 		{
 #ifdef XLOGPREFETCHER_DEBUG_LEVEL
 			elog(XLOGPREFETCHER_DEBUG_LEVEL,
-				 "prefetch of %u/%u/%u block %u suppressed; filtering until LSN %X/%X is replayed (blocks >= %u filtered)",
+				 "prefetch of %u/%u/" UINT64_FORMAT " block %u suppressed; filtering until LSN %X/%X is replayed (blocks >= %u filtered)",
 				 rlocator.spcOid, rlocator.dbOid, rlocator.relNumber, blockno,
 				 LSN_FORMAT_ARGS(filter->filter_until_replayed),
 				 filter->filter_from_block);
@@ -950,7 +950,7 @@ XLogPrefetcherIsFiltered(XLogPrefetcher *prefetcher, RelFileLocator rlocator,
 		{
 #ifdef XLOGPREFETCHER_DEBUG_LEVEL
 			elog(XLOGPREFETCHER_DEBUG_LEVEL,
-				 "prefetch of %u/%u/%u block %u suppressed; filtering until LSN %X/%X is replayed (whole database)",
+				 "prefetch of %u/%u/" UINT64_FORMAT " block %u suppressed; filtering until LSN %X/%X is replayed (whole database)",
 				 rlocator.spcOid, rlocator.dbOid, rlocator.relNumber, blockno,
 				 LSN_FORMAT_ARGS(filter->filter_until_replayed));
 #endif

src/backend/access/transam/xlogrecovery.c

@@ -2228,14 +2228,14 @@ xlog_block_info(StringInfo buf, XLogReaderState *record)
 			continue;
 
 		if (forknum != MAIN_FORKNUM)
-			appendStringInfo(buf, "; blkref #%d: rel %u/%u/%u, fork %u, blk %u",
+			appendStringInfo(buf, "; blkref #%d: rel %u/%u/" UINT64_FORMAT ", fork %u, blk %u",
 							 block_id,
 							 rlocator.spcOid, rlocator.dbOid,
 							 rlocator.relNumber,
 							 forknum,
 							 blk);
 		else
-			appendStringInfo(buf, "; blkref #%d: rel %u/%u/%u, blk %u",
+			appendStringInfo(buf, "; blkref #%d: rel %u/%u/" UINT64_FORMAT ", blk %u",
 							 block_id,
 							 rlocator.spcOid, rlocator.dbOid,
 							 rlocator.relNumber,
@@ -2433,7 +2433,7 @@ verifyBackupPageConsistency(XLogReaderState *record)
 		if (memcmp(replay_image_masked, primary_image_masked, BLCKSZ) != 0)
 		{
 			elog(FATAL,
-				 "inconsistent page found, rel %u/%u/%u, forknum %u, blkno %u",
+				 "inconsistent page found, rel %u/%u/" UINT64_FORMAT ", forknum %u, blkno %u",
 				 rlocator.spcOid, rlocator.dbOid, rlocator.relNumber,
 				 forknum, blkno);
 		}

src/backend/access/transam/xlogutils.c

@@ -619,17 +619,17 @@ CreateFakeRelcacheEntry(RelFileLocator rlocator)
 	rel->rd_rel->relpersistence = RELPERSISTENCE_PERMANENT;
 
 	/* We don't know the name of the relation; use relfilenumber instead */
-	sprintf(RelationGetRelationName(rel), "%u", rlocator.relNumber);
+	sprintf(RelationGetRelationName(rel), UINT64_FORMAT, rlocator.relNumber);
 
 	/*
 	 * We set up the lockRelId in case anything tries to lock the dummy
-	 * relation.  Note that this is fairly bogus since relNumber may be
+	 * relation.  Note that this is fairly bogus since relNumber are completely
 	 * different from the relation's OID.  It shouldn't really matter though.
 	 * In recovery, we are running by ourselves and can't have any lock
 	 * conflicts.  While syncing, we already hold AccessExclusiveLock.
 	 */
 	rel->rd_lockInfo.lockRelId.dbId = rlocator.dbOid;
-	rel->rd_lockInfo.lockRelId.relId = rlocator.relNumber;
+	rel->rd_lockInfo.lockRelId.relId = (Oid) rlocator.relNumber;
 
 	rel->rd_smgr = NULL;
 

src/backend/backup/basebackup.c

@@ -1246,7 +1246,7 @@ sendDir(bbsink *sink, const char *path, int basepathlen, bool sizeonly,
 			if (relForkNum != INIT_FORKNUM)
 			{
 				char		initForkFile[MAXPGPATH];
-				char		relNumber[OIDCHARS + 1];
+				char		relNumber[RELNUMBERCHARS + 1];
 
 				/*
 				 * If any other type of fork, check if there is an init fork

src/backend/catalog/catalog.c

@@ -482,101 +482,6 @@ GetNewOidWithIndex(Relation relation, Oid indexId, AttrNumber oidcolumn)
 	return newOid;
 }
 
-/*
- * GetNewRelFileNumber
- *		Generate a new relfilenumber that is unique within the
- *		database of the given tablespace.
- *
- * If the relfilenumber will also be used as the relation's OID, pass the
- * opened pg_class catalog, and this routine will guarantee that the result
- * is also an unused OID within pg_class.  If the result is to be used only
- * as a relfilenumber for an existing relation, pass NULL for pg_class.
- *
- * As with GetNewOidWithIndex(), there is some theoretical risk of a race
- * condition, but it doesn't seem worth worrying about.
- *
- * Note: we don't support using this in bootstrap mode.  All relations
- * created by bootstrap have preassigned OIDs, so there's no need.
- */
-RelFileNumber
-GetNewRelFileNumber(Oid reltablespace, Relation pg_class, char relpersistence)
-{
-	RelFileLocatorBackend rlocator;
-	char	   *rpath;
-	bool		collides;
-	BackendId	backend;
-
-	/*
-	 * If we ever get here during pg_upgrade, there's something wrong; all
-	 * relfilenumber assignments during a binary-upgrade run should be
-	 * determined by commands in the dump script.
-	 */
-	Assert(!IsBinaryUpgrade);
-
-	switch (relpersistence)
-	{
-		case RELPERSISTENCE_TEMP:
-			backend = BackendIdForTempRelations();
-			break;
-		case RELPERSISTENCE_UNLOGGED:
-		case RELPERSISTENCE_PERMANENT:
-			backend = InvalidBackendId;
-			break;
-		default:
-			elog(ERROR, "invalid relpersistence: %c", relpersistence);
-			return InvalidRelFileNumber;	/* placate compiler */
-	}
-
-	/* This logic should match RelationInitPhysicalAddr */
-	rlocator.locator.spcOid = reltablespace ? reltablespace : MyDatabaseTableSpace;
-	rlocator.locator.dbOid =
-		(rlocator.locator.spcOid == GLOBALTABLESPACE_OID) ?
-		InvalidOid : MyDatabaseId;
-
-	/*
-	 * The relpath will vary based on the backend ID, so we must initialize
-	 * that properly here to make sure that any collisions based on filename
-	 * are properly detected.
-	 */
-	rlocator.backend = backend;
-
-	do
-	{
-		CHECK_FOR_INTERRUPTS();
-
-		/* Generate the OID */
-		if (pg_class)
-			rlocator.locator.relNumber = GetNewOidWithIndex(pg_class, ClassOidIndexId,
-															Anum_pg_class_oid);
-		else
-			rlocator.locator.relNumber = GetNewObjectId();
-
-		/* Check for existing file of same name */
-		rpath = relpath(rlocator, MAIN_FORKNUM);
-
-		if (access(rpath, F_OK) == 0)
-		{
-			/* definite collision */
-			collides = true;
-		}
-		else
-		{
-			/*
-			 * Here we have a little bit of a dilemma: if errno is something
-			 * other than ENOENT, should we declare a collision and loop? In
-			 * practice it seems best to go ahead regardless of the errno.  If
-			 * there is a colliding file we will get an smgr failure when we
-			 * attempt to create the new relation file.
-			 */
-			collides = false;
-		}
-
-		pfree(rpath);
-	} while (collides);
-
-	return rlocator.locator.relNumber;
-}
-
 /*
  * SQL callable interface for GetNewOidWithIndex().  Outside of initdb's
  * direct insertions into catalog tables, and recovering from corruption, this

src/backend/catalog/heap.c

@@ -341,11 +341,19 @@ heap_create(const char *relname,
 	else
 	{
 		/*
-		 * If relfilenumber is unspecified by the caller then create storage
+		 * If relfilenumber is unspecified by the caller then allocate a new
-		 * with oid same as relid.
+		 * one, except for system tables, for which we make the initial
+		 * relfilenumber the same as the table OID. See the comments for
+		 * FirstNormalRelFileNumber for an explanation of why we do this.
 		 */
 		if (!RelFileNumberIsValid(relfilenumber))
-			relfilenumber = relid;
+		{
+			if (relid < FirstNormalObjectId)
+				relfilenumber = relid;
+			else
+				relfilenumber = GetNewRelFileNumber(reltablespace,
+													relpersistence);
+		}
 	}
 
 	/*
@@ -901,7 +909,7 @@ InsertPgClassTuple(Relation pg_class_desc,
 	values[Anum_pg_class_reloftype - 1] = ObjectIdGetDatum(rd_rel->reloftype);
 	values[Anum_pg_class_relowner - 1] = ObjectIdGetDatum(rd_rel->relowner);
 	values[Anum_pg_class_relam - 1] = ObjectIdGetDatum(rd_rel->relam);
-	values[Anum_pg_class_relfilenode - 1] = ObjectIdGetDatum(rd_rel->relfilenode);
+	values[Anum_pg_class_relfilenode - 1] = Int64GetDatum(rd_rel->relfilenode);
 	values[Anum_pg_class_reltablespace - 1] = ObjectIdGetDatum(rd_rel->reltablespace);
 	values[Anum_pg_class_relpages - 1] = Int32GetDatum(rd_rel->relpages);
 	values[Anum_pg_class_reltuples - 1] = Float4GetDatum(rd_rel->reltuples);
@@ -1173,12 +1181,7 @@ heap_create_with_catalog(const char *relname,
 	if (shared_relation && reltablespace != GLOBALTABLESPACE_OID)
 		elog(ERROR, "shared relations must be placed in pg_global tablespace");
 
-	/*
+	/* Allocate an OID for the relation, unless we were told what to use. */
-	 * Allocate an OID for the relation, unless we were told what to use.
-	 *
-	 * The OID will be the relfilenumber as well, so make sure it doesn't
-	 * collide with either pg_class OIDs or existing physical files.
-	 */
 	if (!OidIsValid(relid))
 	{
 		/* Use binary-upgrade override for pg_class.oid and relfilenumber */
@@ -1232,8 +1235,8 @@ heap_create_with_catalog(const char *relname,
 		}
 
 		if (!OidIsValid(relid))
-			relid = GetNewRelFileNumber(reltablespace, pg_class_desc,
+			relid = GetNewOidWithIndex(pg_class_desc, ClassOidIndexId,
-										relpersistence);
+									   Anum_pg_class_oid);
 	}
 
 	/*

src/backend/catalog/index.c

@@ -898,12 +898,7 @@ index_create(Relation heapRelation,
 											collationObjectId,
 											classObjectId);
 
-	/*
+	/* Allocate an OID for the index, unless we were told what to use. */
-	 * Allocate an OID for the index, unless we were told what to use.
-	 *
-	 * The OID will be the relfilenumber as well, so make sure it doesn't
-	 * collide with either pg_class OIDs or existing physical files.
-	 */
 	if (!OidIsValid(indexRelationId))
 	{
 		/* Use binary-upgrade override for pg_class.oid and relfilenumber */
@@ -935,8 +930,8 @@ index_create(Relation heapRelation,
 		}
 		else
 		{
-			indexRelationId =
+			indexRelationId = GetNewOidWithIndex(pg_class, ClassOidIndexId,
-				GetNewRelFileNumber(tableSpaceId, pg_class, relpersistence);
+												 Anum_pg_class_oid);
 		}
 	}
 

src/backend/catalog/storage.c

@@ -968,6 +968,10 @@ smgr_redo(XLogReaderState *record)
 		xl_smgr_create *xlrec = (xl_smgr_create *) XLogRecGetData(record);
 		SMgrRelation reln;
 
+		if (xlrec->rlocator.relNumber > ShmemVariableCache->nextRelFileNumber)
+			elog(ERROR, "unexpected relnumber " UINT64_FORMAT " that is bigger than nextRelFileNumber " UINT64_FORMAT,
+				 xlrec->rlocator.relNumber, ShmemVariableCache->nextRelFileNumber);
+
 		reln = smgropen(xlrec->rlocator, InvalidBackendId);
 		smgrcreate(reln, xlrec->forkNum, true);
 	}
@@ -981,6 +985,10 @@ smgr_redo(XLogReaderState *record)
 		int			nforks = 0;
 		bool		need_fsm_vacuum = false;
 
+		if (xlrec->rlocator.relNumber > ShmemVariableCache->nextRelFileNumber)
+			elog(ERROR, "unexpected relnumber " UINT64_FORMAT "that is bigger than nextRelFileNumber " UINT64_FORMAT,
+				 xlrec->rlocator.relNumber, ShmemVariableCache->nextRelFileNumber);
+
 		reln = smgropen(xlrec->rlocator, InvalidBackendId);
 
 		/*

src/backend/commands/tablecmds.c

@@ -14375,10 +14375,14 @@ ATExecSetTableSpace(Oid tableOid, Oid newTableSpace, LOCKMODE lockmode)
 	}
 
 	/*
-	 * Relfilenumbers are not unique in databases across tablespaces, so we
+	 * Generate a new relfilenumber.  We cannot reuse the old relfilenumber
-	 * need to allocate a new one in the new tablespace.
+	 * because of the possibility that that relation will be moved back to the
+	 * original tablespace before the next checkpoint. At that point, the
+	 * first segment of the main fork won't have been unlinked yet, and an
+	 * attempt to create new relation storage with that same relfilenumber
+	 * will fail.
 	 */
-	newrelfilenumber = GetNewRelFileNumber(newTableSpace, NULL,
+	newrelfilenumber = GetNewRelFileNumber(newTableSpace,
 										   rel->rd_rel->relpersistence);
 
 	/* Open old and new relation */

src/backend/commands/tablespace.c

@@ -267,7 +267,7 @@ CreateTableSpace(CreateTableSpaceStmt *stmt)
 	 * parts.
 	 */
 	if (strlen(location) + 1 + strlen(TABLESPACE_VERSION_DIRECTORY) + 1 +
-		OIDCHARS + 1 + OIDCHARS + 1 + FORKNAMECHARS + 1 + OIDCHARS > MAXPGPATH)
+		OIDCHARS + 1 + RELNUMBERCHARS + 1 + FORKNAMECHARS + 1 + OIDCHARS > MAXPGPATH)
 		ereport(ERROR,
 				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
 				 errmsg("tablespace location \"%s\" is too long",

src/backend/nodes/gen_node_support.pl

@@ -961,12 +961,12 @@ _read${n}(void)
 			print $off "\tWRITE_UINT_FIELD($f);\n";
 			print $rff "\tREAD_UINT_FIELD($f);\n" unless $no_read;
 		}
-		elsif ($t eq 'uint64')
+		elsif ($t eq 'uint64' || $t eq 'RelFileNumber')
 		{
 			print $off "\tWRITE_UINT64_FIELD($f);\n";
 			print $rff "\tREAD_UINT64_FIELD($f);\n" unless $no_read;
 		}
-		elsif ($t eq 'Oid' || $t eq 'RelFileNumber')
+		elsif ($t eq 'Oid')
 		{
 			print $off "\tWRITE_OID_FIELD($f);\n";
 			print $rff "\tREAD_OID_FIELD($f);\n" unless $no_read;

src/backend/replication/logical/decode.c

@@ -154,6 +154,7 @@ xlog_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
 			break;
 		case XLOG_NOOP:
 		case XLOG_NEXTOID:
+		case XLOG_NEXT_RELFILENUMBER:
 		case XLOG_SWITCH:
 		case XLOG_BACKUP_END:
 		case XLOG_PARAMETER_CHANGE:

src/backend/replication/logical/reorderbuffer.c

@@ -4932,7 +4932,7 @@ DisplayMapping(HTAB *tuplecid_data)
 	hash_seq_init(&hstat, tuplecid_data);
 	while ((ent = (ReorderBufferTupleCidEnt *) hash_seq_search(&hstat)) != NULL)
 	{
-		elog(DEBUG3, "mapping: node: %u/%u/%u tid: %u/%u cmin: %u, cmax: %u",
+		elog(DEBUG3, "mapping: node: %u/%u/" UINT64_FORMAT " tid: %u/%u cmin: %u, cmax: %u",
 			 ent->key.rlocator.dbOid,
 			 ent->key.rlocator.spcOid,
 			 ent->key.rlocator.relNumber,

src/backend/storage/file/reinit.c

@@ -31,7 +31,7 @@ static void ResetUnloggedRelationsInDbspaceDir(const char *dbspacedirname,
 
 typedef struct
 {
-	Oid			reloid;			/* hash key */
+	RelFileNumber		relnumber;			/* hash key */
 } unlogged_relation_entry;
 
 /*
@@ -184,10 +184,10 @@ ResetUnloggedRelationsInDbspaceDir(const char *dbspacedirname, int op)
 		 * need to be reset.  Otherwise, this cleanup operation would be
 		 * O(n^2).
 		 */
-		ctl.keysize = sizeof(Oid);
+		ctl.keysize = sizeof(RelFileNumber);
 		ctl.entrysize = sizeof(unlogged_relation_entry);
 		ctl.hcxt = CurrentMemoryContext;
-		hash = hash_create("unlogged relation OIDs", 32, &ctl,
+		hash = hash_create("unlogged relation RelFileNumbers", 32, &ctl,
 						   HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
 
 		/* Scan the directory. */
@@ -208,10 +208,10 @@ ResetUnloggedRelationsInDbspaceDir(const char *dbspacedirname, int op)
 				continue;
 
 			/*
-			 * Put the OID portion of the name into the hash table, if it
+			 * Put the RELFILENUMBER portion of the name into the hash table,
-			 * isn't already.
+			 * if it isn't already.
 			 */
-			ent.reloid = atooid(de->d_name);
+			ent.relnumber = atorelnumber(de->d_name);
 			(void) hash_search(hash, &ent, HASH_ENTER, NULL);
 		}
 
@@ -248,10 +248,10 @@ ResetUnloggedRelationsInDbspaceDir(const char *dbspacedirname, int op)
 				continue;
 
 			/*
-			 * See whether the OID portion of the name shows up in the hash
+			 * See whether the RELFILENUMBER portion of the name shows up in
-			 * table.  If so, nuke it!
+			 * the hash table.  If so, nuke it!
 			 */
-			ent.reloid = atooid(de->d_name);
+			ent.relnumber = atorelnumber(de->d_name);
 			if (hash_search(hash, &ent, HASH_FIND, NULL))
 			{
 				snprintf(rm_path, sizeof(rm_path), "%s/%s",
@@ -286,7 +286,7 @@ ResetUnloggedRelationsInDbspaceDir(const char *dbspacedirname, int op)
 		{
 			ForkNumber	forkNum;
 			int			relnumchars;
-			char		relnumbuf[OIDCHARS + 1];
+			char		relnumbuf[RELNUMBERCHARS + 1];
 			char		srcpath[MAXPGPATH * 2];
 			char		dstpath[MAXPGPATH];
 
@@ -329,7 +329,7 @@ ResetUnloggedRelationsInDbspaceDir(const char *dbspacedirname, int op)
 		{
 			ForkNumber	forkNum;
 			int			relnumchars;
-			char		relnumbuf[OIDCHARS + 1];
+			char		relnumbuf[RELNUMBERCHARS + 1];
 			char		mainpath[MAXPGPATH];
 
 			/* Skip anything that doesn't look like a relation data file. */
@@ -372,8 +372,8 @@ ResetUnloggedRelationsInDbspaceDir(const char *dbspacedirname, int op)
  * for a non-temporary relation and false otherwise.
  *
  * NB: If this function returns true, the caller is entitled to assume that
- * *relnumchars has been set to a value no more than OIDCHARS, and thus
+ * *relnumchars has been set to a value no more than RELNUMBERCHARS, and thus
- * that a buffer of OIDCHARS+1 characters is sufficient to hold the
+ * that a buffer of RELNUMBERCHARS+1 characters is sufficient to hold the
  * RelFileNumber portion of the filename.  This is critical to protect against
  * a possible buffer overrun.
  */
@@ -386,7 +386,7 @@ parse_filename_for_nontemp_relation(const char *name, int *relnumchars,
 	/* Look for a non-empty string of digits (that isn't too long). */
 	for (pos = 0; isdigit((unsigned char) name[pos]); ++pos)
 		;
-	if (pos == 0 || pos > OIDCHARS)
+	if (pos == 0 || pos > RELNUMBERCHARS)
 		return false;
 	*relnumchars = pos;
 

src/backend/storage/freespace/fsmpage.c

@@ -273,7 +273,7 @@ restart:
 			BlockNumber blknum;
 
 			BufferGetTag(buf, &rlocator, &forknum, &blknum);
-			elog(DEBUG1, "fixing corrupt FSM block %u, relation %u/%u/%u",
+			elog(DEBUG1, "fixing corrupt FSM block %u, relation %u/%u/" UINT64_FORMAT,
 				 blknum, rlocator.spcOid, rlocator.dbOid, rlocator.relNumber);
 
 			/* make sure we hold an exclusive lock */

src/backend/storage/lmgr/lwlocknames.txt

@@ -53,3 +53,4 @@ XactTruncationLock					44
 # 45 was XactTruncationLock until removal of BackendRandomLock
 WrapLimitsVacuumLock				46
 NotifyQueueTailLock					47
+RelFileNumberGenLock                48

src/backend/storage/smgr/md.c

@@ -257,6 +257,13 @@ mdcreate(SMgrRelation reln, ForkNumber forknum, bool isRedo)
  * next checkpoint, we prevent reassignment of the relfilenumber until it's
  * safe, because relfilenumber assignment skips over any existing file.
  *
+ * XXX. Although all of this was true when relfilenumbers were 32 bits wide,
+ * they are now 56 bits wide and do not wrap around, so in the future we can
+ * change the code to immediately unlink the first segment of the relation
+ * along with all the others. We still do reuse relfilenumbers when createdb()
+ * is performed using the file-copy method or during movedb(), but the scenario
+ * described above can only happen when creating a new relation.
+ *
  * We do not need to go through this dance for temp relations, though, because
  * we never make WAL entries for temp rels, and so a temp rel poses no threat
  * to the health of a regular rel that has taken over its relfilenumber.

src/backend/storage/smgr/smgr.c

@@ -154,7 +154,7 @@ smgropen(RelFileLocator rlocator, BackendId backend)
 		/* First time through: initialize the hash table */
 		HASHCTL		ctl;
 
-		ctl.keysize = sizeof(RelFileLocatorBackend);
+		ctl.keysize = SizeOfRelFileLocatorBackend;
 		ctl.entrysize = sizeof(SMgrRelationData);
 		SMgrRelationHash = hash_create("smgr relation table", 400,
 									   &ctl, HASH_ELEM | HASH_BLOBS);

src/backend/utils/adt/dbsize.c

@@ -878,7 +878,7 @@ pg_relation_filenode(PG_FUNCTION_ARGS)
 	if (!RelFileNumberIsValid(result))
 		PG_RETURN_NULL();
 
-	PG_RETURN_OID(result);
+	PG_RETURN_INT64(result);
 }
 
 /*
@@ -898,9 +898,12 @@ Datum
 pg_filenode_relation(PG_FUNCTION_ARGS)
 {
 	Oid			reltablespace = PG_GETARG_OID(0);
-	RelFileNumber relfilenumber = PG_GETARG_OID(1);
+	RelFileNumber relfilenumber = PG_GETARG_INT64(1);
 	Oid			heaprel;
 
+	/* check whether the relfilenumber is within a valid range */
+	CHECK_RELFILENUMBER_RANGE(relfilenumber);
+
 	/* test needed so RelidByRelfilenumber doesn't misbehave */
 	if (!RelFileNumberIsValid(relfilenumber))
 		PG_RETURN_NULL();

src/backend/utils/adt/pg_upgrade_support.c

@@ -17,6 +17,7 @@
 #include "catalog/pg_type.h"
 #include "commands/extension.h"
 #include "miscadmin.h"
+#include "storage/relfilelocator.h"
 #include "utils/array.h"
 #include "utils/builtins.h"
 
@@ -98,10 +99,12 @@ binary_upgrade_set_next_heap_pg_class_oid(PG_FUNCTION_ARGS)
 Datum
 binary_upgrade_set_next_heap_relfilenode(PG_FUNCTION_ARGS)
 {
-	RelFileNumber relfilenumber = PG_GETARG_OID(0);
+	RelFileNumber relfilenumber = PG_GETARG_INT64(0);
 
 	CHECK_IS_BINARY_UPGRADE;
+	CHECK_RELFILENUMBER_RANGE(relfilenumber);
 	binary_upgrade_next_heap_pg_class_relfilenumber = relfilenumber;
+	SetNextRelFileNumber(relfilenumber + 1);
 
 	PG_RETURN_VOID();
 }
@@ -120,10 +123,12 @@ binary_upgrade_set_next_index_pg_class_oid(PG_FUNCTION_ARGS)
 Datum
 binary_upgrade_set_next_index_relfilenode(PG_FUNCTION_ARGS)
 {
-	RelFileNumber relfilenumber = PG_GETARG_OID(0);
+	RelFileNumber relfilenumber = PG_GETARG_INT64(0);
 
 	CHECK_IS_BINARY_UPGRADE;
+	CHECK_RELFILENUMBER_RANGE(relfilenumber);
 	binary_upgrade_next_index_pg_class_relfilenumber = relfilenumber;
+	SetNextRelFileNumber(relfilenumber + 1);
 
 	PG_RETURN_VOID();
 }
@@ -142,10 +147,12 @@ binary_upgrade_set_next_toast_pg_class_oid(PG_FUNCTION_ARGS)
 Datum
 binary_upgrade_set_next_toast_relfilenode(PG_FUNCTION_ARGS)
 {
-	RelFileNumber relfilenumber = PG_GETARG_OID(0);
+	RelFileNumber relfilenumber = PG_GETARG_INT64(0);
 
 	CHECK_IS_BINARY_UPGRADE;
+	CHECK_RELFILENUMBER_RANGE(relfilenumber);
 	binary_upgrade_next_toast_pg_class_relfilenumber = relfilenumber;
+	SetNextRelFileNumber(relfilenumber + 1);
 
 	PG_RETURN_VOID();
 }

src/backend/utils/cache/relcache.c

@@ -3712,7 +3712,7 @@ RelationSetNewRelfilenumber(Relation relation, char persistence)
 	{
 		/* Allocate a new relfilenumber */
 		newrelfilenumber = GetNewRelFileNumber(relation->rd_rel->reltablespace,
-											   NULL, persistence);
+											   persistence);
 	}
 	else if (relation->rd_rel->relkind == RELKIND_INDEX)
 	{

src/backend/utils/cache/relfilenumbermap.c

@@ -196,7 +196,7 @@ RelidByRelfilenumber(Oid reltablespace, RelFileNumber relfilenumber)
 
 		/* set scan arguments */
 		skey[0].sk_argument = ObjectIdGetDatum(reltablespace);
-		skey[1].sk_argument = ObjectIdGetDatum(relfilenumber);
+		skey[1].sk_argument = Int64GetDatum((int64) relfilenumber);
 
 		scandesc = systable_beginscan(relation,
 									  ClassTblspcRelfilenodeIndexId,
@@ -213,7 +213,7 @@ RelidByRelfilenumber(Oid reltablespace, RelFileNumber relfilenumber)
 
 			if (found)
 				elog(ERROR,
-					 "unexpected duplicate for tablespace %u, relfilenumber %u",
+					 "unexpected duplicate for tablespace %u, relfilenumber " UINT64_FORMAT,
 					 reltablespace, relfilenumber);
 			found = true;
 

src/backend/utils/misc/pg_controldata.c

@@ -79,8 +79,8 @@ pg_control_system(PG_FUNCTION_ARGS)
 Datum
 pg_control_checkpoint(PG_FUNCTION_ARGS)
 {
-	Datum		values[18];
+	Datum		values[19];
-	bool		nulls[18];
+	bool		nulls[19];
 	TupleDesc	tupdesc;
 	HeapTuple	htup;
 	ControlFileData *ControlFile;
@@ -129,6 +129,8 @@ pg_control_checkpoint(PG_FUNCTION_ARGS)
 					   XIDOID, -1, 0);
 	TupleDescInitEntry(tupdesc, (AttrNumber) 18, "checkpoint_time",
 					   TIMESTAMPTZOID, -1, 0);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 19, "next_relfilenumber",
+					   INT8OID, -1, 0);
 	tupdesc = BlessTupleDesc(tupdesc);
 
 	/* Read the control file. */
@@ -202,6 +204,9 @@ pg_control_checkpoint(PG_FUNCTION_ARGS)
 	values[17] = TimestampTzGetDatum(time_t_to_timestamptz(ControlFile->checkPointCopy.time));
 	nulls[17] = false;
 
+	values[18] = Int64GetDatum((int64) ControlFile->checkPointCopy.nextRelFileNumber);
+	nulls[18] = false;
+
 	htup = heap_form_tuple(tupdesc, values, nulls);
 
 	PG_RETURN_DATUM(HeapTupleGetDatum(htup));

src/bin/pg_checksums/pg_checksums.c

@@ -485,9 +485,7 @@ main(int argc, char *argv[])
 				mode = PG_MODE_ENABLE;
 				break;
 			case 'f':
-				if (!option_parse_int(optarg, "-f/--filenode", 0,
+				if (!option_parse_relfilenumber(optarg, "-f/--filenode"))
-									  INT_MAX,
-									  NULL))
 					exit(1);
 				only_filenode = pstrdup(optarg);
 				break;

src/bin/pg_controldata/pg_controldata.c

@@ -250,6 +250,8 @@ main(int argc, char *argv[])
 	printf(_("Latest checkpoint's NextXID:          %u:%u\n"),
 		   EpochFromFullTransactionId(ControlFile->checkPointCopy.nextXid),
 		   XidFromFullTransactionId(ControlFile->checkPointCopy.nextXid));
+	printf(_("Latest checkpoint's NextRelFileNumber:%llu\n"),
+		   (unsigned long long) ControlFile->checkPointCopy.nextRelFileNumber);
 	printf(_("Latest checkpoint's NextOID:          %u\n"),
 		   ControlFile->checkPointCopy.nextOid);
 	printf(_("Latest checkpoint's NextMultiXactId:  %u\n"),

src/bin/pg_dump/pg_dump.c

@@ -3184,15 +3184,15 @@ dumpDatabase(Archive *fout)
 							  atooid(PQgetvalue(lo_res, i, ii_oid)));
 
 			oid = atooid(PQgetvalue(lo_res, i, ii_oid));
-			relfilenumber = atooid(PQgetvalue(lo_res, i, ii_relfilenode));
+			relfilenumber = atorelnumber(PQgetvalue(lo_res, i, ii_relfilenode));
 
 			if (oid == LargeObjectRelationId)
 				appendPQExpBuffer(loOutQry,
-								  "SELECT pg_catalog.binary_upgrade_set_next_heap_relfilenode('%u'::pg_catalog.oid);\n",
+								  "SELECT pg_catalog.binary_upgrade_set_next_heap_relfilenode('" UINT64_FORMAT "'::pg_catalog.int8);\n",
 								  relfilenumber);
 			else if (oid == LargeObjectLOidPNIndexId)
 				appendPQExpBuffer(loOutQry,
-								  "SELECT pg_catalog.binary_upgrade_set_next_index_relfilenode('%u'::pg_catalog.oid);\n",
+								  "SELECT pg_catalog.binary_upgrade_set_next_index_relfilenode('" UINT64_FORMAT "'::pg_catalog.int8);\n",
 								  relfilenumber);
 		}
 
@@ -4877,16 +4877,16 @@ binary_upgrade_set_pg_class_oids(Archive *fout,
 
 	relkind = *PQgetvalue(upgrade_res, 0, PQfnumber(upgrade_res, "relkind"));
 
-	relfilenumber = atooid(PQgetvalue(upgrade_res, 0,
+	relfilenumber = atorelnumber(PQgetvalue(upgrade_res, 0,
-									  PQfnumber(upgrade_res, "relfilenode")));
+											PQfnumber(upgrade_res, "relfilenode")));
 	toast_oid = atooid(PQgetvalue(upgrade_res, 0,
 								  PQfnumber(upgrade_res, "reltoastrelid")));
-	toast_relfilenumber = atooid(PQgetvalue(upgrade_res, 0,
+	toast_relfilenumber = atorelnumber(PQgetvalue(upgrade_res, 0,
-											PQfnumber(upgrade_res, "toast_relfilenode")));
+												  PQfnumber(upgrade_res, "toast_relfilenode")));
 	toast_index_oid = atooid(PQgetvalue(upgrade_res, 0,
 										PQfnumber(upgrade_res, "indexrelid")));
-	toast_index_relfilenumber = atooid(PQgetvalue(upgrade_res, 0,
+	toast_index_relfilenumber = atorelnumber(PQgetvalue(upgrade_res, 0,
-												  PQfnumber(upgrade_res, "toast_index_relfilenode")));
+														PQfnumber(upgrade_res, "toast_index_relfilenode")));
 
 	appendPQExpBufferStr(upgrade_buffer,
 						 "\n-- For binary upgrade, must preserve pg_class oids and relfilenodes\n");
@@ -4904,7 +4904,7 @@ binary_upgrade_set_pg_class_oids(Archive *fout,
 		 */
 		if (RelFileNumberIsValid(relfilenumber) && relkind != RELKIND_PARTITIONED_TABLE)
 			appendPQExpBuffer(upgrade_buffer,
-							  "SELECT pg_catalog.binary_upgrade_set_next_heap_relfilenode('%u'::pg_catalog.oid);\n",
+							  "SELECT pg_catalog.binary_upgrade_set_next_heap_relfilenode('" UINT64_FORMAT "'::pg_catalog.int8);\n",
 							  relfilenumber);
 
 		/*
@@ -4918,7 +4918,7 @@ binary_upgrade_set_pg_class_oids(Archive *fout,
 							  "SELECT pg_catalog.binary_upgrade_set_next_toast_pg_class_oid('%u'::pg_catalog.oid);\n",
 							  toast_oid);
 			appendPQExpBuffer(upgrade_buffer,
-							  "SELECT pg_catalog.binary_upgrade_set_next_toast_relfilenode('%u'::pg_catalog.oid);\n",
+							  "SELECT pg_catalog.binary_upgrade_set_next_toast_relfilenode('" UINT64_FORMAT "'::pg_catalog.int8);\n",
 							  toast_relfilenumber);
 
 			/* every toast table has an index */
@@ -4926,7 +4926,7 @@ binary_upgrade_set_pg_class_oids(Archive *fout,
 							  "SELECT pg_catalog.binary_upgrade_set_next_index_pg_class_oid('%u'::pg_catalog.oid);\n",
 							  toast_index_oid);
 			appendPQExpBuffer(upgrade_buffer,
-							  "SELECT pg_catalog.binary_upgrade_set_next_index_relfilenode('%u'::pg_catalog.oid);\n",
+							  "SELECT pg_catalog.binary_upgrade_set_next_index_relfilenode('" UINT64_FORMAT "'::pg_catalog.int8);\n",
 							  toast_index_relfilenumber);
 		}
 
@@ -4939,7 +4939,7 @@ binary_upgrade_set_pg_class_oids(Archive *fout,
 						  "SELECT pg_catalog.binary_upgrade_set_next_index_pg_class_oid('%u'::pg_catalog.oid);\n",
 						  pg_class_oid);
 		appendPQExpBuffer(upgrade_buffer,
-						  "SELECT pg_catalog.binary_upgrade_set_next_index_relfilenode('%u'::pg_catalog.oid);\n",
+						  "SELECT pg_catalog.binary_upgrade_set_next_index_relfilenode('" UINT64_FORMAT "'::pg_catalog.int8);\n",
 						  relfilenumber);
 	}
 

src/bin/pg_rewind/filemap.c

@@ -538,7 +538,7 @@ isRelDataFile(const char *path)
 	segNo = 0;
 	matched = false;
 
-	nmatch = sscanf(path, "global/%u.%u", &rlocator.relNumber, &segNo);
+	nmatch = sscanf(path, "global/" UINT64_FORMAT ".%u", &rlocator.relNumber, &segNo);
 	if (nmatch == 1 || nmatch == 2)
 	{
 		rlocator.spcOid = GLOBALTABLESPACE_OID;
@@ -547,7 +547,7 @@ isRelDataFile(const char *path)
 	}
 	else
 	{
-		nmatch = sscanf(path, "base/%u/%u.%u",
+		nmatch = sscanf(path, "base/%u/" UINT64_FORMAT ".%u",
 						&rlocator.dbOid, &rlocator.relNumber, &segNo);
 		if (nmatch == 2 || nmatch == 3)
 		{
@@ -556,7 +556,7 @@ isRelDataFile(const char *path)
 		}
 		else
 		{
-			nmatch = sscanf(path, "pg_tblspc/%u/" TABLESPACE_VERSION_DIRECTORY "/%u/%u.%u",
+			nmatch = sscanf(path, "pg_tblspc/%u/" TABLESPACE_VERSION_DIRECTORY "/%u/" UINT64_FORMAT ".%u",
 							&rlocator.spcOid, &rlocator.dbOid, &rlocator.relNumber,
 							&segNo);
 			if (nmatch == 3 || nmatch == 4)

src/bin/pg_upgrade/info.c

@@ -527,7 +527,8 @@ get_rel_infos(ClusterInfo *cluster, DbInfo *dbinfo)
 		relname = PQgetvalue(res, relnum, i_relname);
 		curr->relname = pg_strdup(relname);
 
-		curr->relfilenumber = atooid(PQgetvalue(res, relnum, i_relfilenumber));
+		curr->relfilenumber =
+			atorelnumber(PQgetvalue(res, relnum, i_relfilenumber));
 		curr->tblsp_alloc = false;
 
 		/* Is the tablespace oid non-default? */

src/bin/pg_upgrade/pg_upgrade.c

@@ -15,10 +15,8 @@
  *	oids are the same between old and new clusters.  This is important
  *	because toast oids are stored as toast pointers in user tables.
  *
- *	While pg_class.oid and pg_class.relfilenode are initially the same in a
+ *	We control assignments of pg_class.relfilenode because we want the
- *	cluster, they can diverge due to CLUSTER, REINDEX, or VACUUM FULL. We
+ *	filenames to match between the old and new cluster.
- *	control assignments of pg_class.relfilenode because we want the filenames
- *	to match between the old and new cluster.
  *
  *	We control assignment of pg_tablespace.oid because we want the oid to match
  *	between the old and new cluster.

src/bin/pg_upgrade/relfilenumber.c

@@ -190,14 +190,14 @@ transfer_relfile(FileNameMap *map, const char *type_suffix, bool vm_must_add_fro
 		else
 			snprintf(extent_suffix, sizeof(extent_suffix), ".%d", segno);
 
-		snprintf(old_file, sizeof(old_file), "%s%s/%u/%u%s%s",
+		snprintf(old_file, sizeof(old_file), "%s%s/%u/" UINT64_FORMAT "%s%s",
 				 map->old_tablespace,
 				 map->old_tablespace_suffix,
 				 map->db_oid,
 				 map->relfilenumber,
 				 type_suffix,
 				 extent_suffix);
-		snprintf(new_file, sizeof(new_file), "%s%s/%u/%u%s%s",
+		snprintf(new_file, sizeof(new_file), "%s%s/%u/" UINT64_FORMAT "%s%s",
 				 map->new_tablespace,
 				 map->new_tablespace_suffix,
 				 map->db_oid,

src/bin/pg_waldump/pg_waldump.c

@@ -884,7 +884,7 @@ main(int argc, char **argv)
 				}
 				break;
 			case 'R':
-				if (sscanf(optarg, "%u/%u/%u",
+				if (sscanf(optarg, "%u/%u/" UINT64_FORMAT,
 						   &config.filter_by_relation.spcOid,
 						   &config.filter_by_relation.dbOid,
 						   &config.filter_by_relation.relNumber) != 3 ||

src/bin/scripts/t/090_reindexdb.pl

@@ -40,7 +40,7 @@ my $toast_index = $node->safe_psql('postgres',
 # REINDEX operations.  A set of relfilenodes is saved from the catalogs
 # and then compared with pg_class.
 $node->safe_psql('postgres',
-	'CREATE TABLE index_relfilenodes (parent regclass, indname text, indoid oid, relfilenode oid);'
+	'CREATE TABLE index_relfilenodes (parent regclass, indname text, indoid oid, relfilenode int8);'
 );
 # Save the relfilenode of a set of toast indexes, one from the catalog
 # pg_constraint and one from the test table.

src/common/relpath.c

@@ -149,10 +149,10 @@ GetRelationPath(Oid dbOid, Oid spcOid, RelFileNumber relNumber,
 		Assert(dbOid == 0);
 		Assert(backendId == InvalidBackendId);
 		if (forkNumber != MAIN_FORKNUM)
-			path = psprintf("global/%u_%s",
+			path = psprintf("global/" UINT64_FORMAT "_%s",
 							relNumber, forkNames[forkNumber]);
 		else
-			path = psprintf("global/%u", relNumber);
+			path = psprintf("global/" UINT64_FORMAT, relNumber);
 	}
 	else if (spcOid == DEFAULTTABLESPACE_OID)
 	{
@@ -160,21 +160,21 @@ GetRelationPath(Oid dbOid, Oid spcOid, RelFileNumber relNumber,
 		if (backendId == InvalidBackendId)
 		{
 			if (forkNumber != MAIN_FORKNUM)
-				path = psprintf("base/%u/%u_%s",
+				path = psprintf("base/%u/" UINT64_FORMAT "_%s",
 								dbOid, relNumber,
 								forkNames[forkNumber]);
 			else
-				path = psprintf("base/%u/%u",
+				path = psprintf("base/%u/" UINT64_FORMAT,
 								dbOid, relNumber);
 		}
 		else
 		{
 			if (forkNumber != MAIN_FORKNUM)
-				path = psprintf("base/%u/t%d_%u_%s",
+				path = psprintf("base/%u/t%d_" UINT64_FORMAT "_%s",
 								dbOid, backendId, relNumber,
 								forkNames[forkNumber]);
 			else
-				path = psprintf("base/%u/t%d_%u",
+				path = psprintf("base/%u/t%d_" UINT64_FORMAT,
 								dbOid, backendId, relNumber);
 		}
 	}
@@ -184,24 +184,24 @@ GetRelationPath(Oid dbOid, Oid spcOid, RelFileNumber relNumber,
 		if (backendId == InvalidBackendId)
 		{
 			if (forkNumber != MAIN_FORKNUM)
-				path = psprintf("pg_tblspc/%u/%s/%u/%u_%s",
+				path = psprintf("pg_tblspc/%u/%s/%u/" UINT64_FORMAT "_%s",
 								spcOid, TABLESPACE_VERSION_DIRECTORY,
 								dbOid, relNumber,
 								forkNames[forkNumber]);
 			else
-				path = psprintf("pg_tblspc/%u/%s/%u/%u",
+				path = psprintf("pg_tblspc/%u/%s/%u/" UINT64_FORMAT,
 								spcOid, TABLESPACE_VERSION_DIRECTORY,
 								dbOid, relNumber);
 		}
 		else
 		{
 			if (forkNumber != MAIN_FORKNUM)
-				path = psprintf("pg_tblspc/%u/%s/%u/t%d_%u_%s",
+				path = psprintf("pg_tblspc/%u/%s/%u/t%d_" UINT64_FORMAT "_%s",
 								spcOid, TABLESPACE_VERSION_DIRECTORY,
 								dbOid, backendId, relNumber,
 								forkNames[forkNumber]);
 			else
-				path = psprintf("pg_tblspc/%u/%s/%u/t%d_%u",
+				path = psprintf("pg_tblspc/%u/%s/%u/t%d_" UINT64_FORMAT,
 								spcOid, TABLESPACE_VERSION_DIRECTORY,
 								dbOid, backendId, relNumber);
 		}

src/fe_utils/option_utils.c

@@ -13,6 +13,7 @@
 #include "postgres_fe.h"
 
 #include "common/logging.h"
+#include "common/relpath.h"
 #include "common/string.h"
 #include "fe_utils/option_utils.h"
 
@@ -82,3 +83,42 @@ option_parse_int(const char *optarg, const char *optname,
 		*result = val;
 	return true;
 }
+
+/*
+ * option_parse_relfilenumber
+ *
+ * Parse relfilenumber value for an option.  If the parsing is successful,
+ * returns; if parsing fails, returns false.
+ */
+bool
+option_parse_relfilenumber(const char *optarg, const char *optname)
+{
+	char	   *endptr;
+	uint64		val;
+
+	errno = 0;
+	val = strtou64(optarg, &endptr, 10);
+
+	/*
+	 * Skip any trailing whitespace; if anything but whitespace remains before
+	 * the terminating character, fail.
+	 */
+	while (*endptr != '\0' && isspace((unsigned char) *endptr))
+		endptr++;
+
+	if (*endptr != '\0')
+	{
+		pg_log_error("invalid value \"%s\" for option %s",
+					 optarg, optname);
+		return false;
+	}
+
+	if (val > MAX_RELFILENUMBER)
+	{
+		pg_log_error("%s must be in range " UINT64_FORMAT ".." UINT64_FORMAT,
+					 optname, UINT64CONST(0), MAX_RELFILENUMBER);
+		return false;
+	}
+
+	return true;
+}

src/include/access/transam.h

@@ -15,6 +15,7 @@
 #define TRANSAM_H
 
 #include "access/xlogdefs.h"
+#include "common/relpath.h"
 
 
 /* ----------------
@@ -196,6 +197,33 @@ FullTransactionIdAdvance(FullTransactionId *dest)
 #define FirstUnpinnedObjectId	12000
 #define FirstNormalObjectId		16384
 
+/* ----------
+ * RelFileNumbers are normally assigned sequentially beginning with
+ * FirstNormalRelFileNumber, but for system tables the initial RelFileNumber
+ * is equal to the table OID. This scheme allows pg_upgrade to work: we expect
+ * that the new cluster will contain only system tables, and that none of those
+ * will have previously been rewritten, so any RelFileNumber which is in use
+ * in both the old and new clusters will be used for the same relation in both
+ * places.
+ *
+ * This is important because pg_upgrade can't reactively move conflicting
+ * relations out of the way. If it tries to set the RelFileNumber for a
+ * relation to some value that's already in use by a different relation, the
+ * upgrade will just fail. It's OK if the same RelFileNumber is used for the
+ * same relation, though, since then nothing needs to be changed.
+ * ----------
+ */
+#define FirstNormalRelFileNumber	((RelFileNumber) 100000)
+
+#define CHECK_RELFILENUMBER_RANGE(relfilenumber)				\
+do {																\
+	if ((relfilenumber) < 0 || (relfilenumber) > MAX_RELFILENUMBER)	\
+		ereport(ERROR,												\
+				errcode(ERRCODE_INVALID_PARAMETER_VALUE),			\
+				errmsg("relfilenumber %llu is out of range",	\
+						(unsigned long long) (relfilenumber))); \
+} while (0)
+
 /*
  * VariableCache is a data structure in shared memory that is used to track
  * OID and XID assignment state.  For largely historical reasons, there is
@@ -214,6 +242,15 @@ typedef struct VariableCacheData
 	Oid			nextOid;		/* next OID to assign */
 	uint32		oidCount;		/* OIDs available before must do XLOG work */
 
+	/*
+	 * These fields are protected by RelFileNumberGenLock.
+	 */
+	RelFileNumber nextRelFileNumber;	/* next relfilenumber to assign */
+	RelFileNumber loggedRelFileNumber;	/* last logged relfilenumber */
+	RelFileNumber flushedRelFileNumber;	/* last flushed relfilenumber */
+	XLogRecPtr	loggedRelFileNumberRecPtr;	/* xlog record pointer w.r.t.
+											 * loggedRelFileNumber */
+
 	/*
 	 * These fields are protected by XidGenLock.
 	 */
@@ -293,6 +330,9 @@ extern void SetTransactionIdLimit(TransactionId oldest_datfrozenxid,
 extern void AdvanceOldestClogXid(TransactionId oldest_datfrozenxid);
 extern bool ForceTransactionIdLimitUpdate(void);
 extern Oid	GetNewObjectId(void);
+extern RelFileNumber GetNewRelFileNumber(Oid reltablespace,
+										 char relpersistence);
+extern void SetNextRelFileNumber(RelFileNumber relnumber);
 extern void StopGeneratingPinnedObjectIds(void);
 
 #ifdef USE_ASSERT_CHECKING

src/include/access/xlog.h

@@ -236,6 +236,7 @@ extern void CreateCheckPoint(int flags);
 extern bool CreateRestartPoint(int flags);
 extern WALAvailability GetWALAvailability(XLogRecPtr targetLSN);
 extern void XLogPutNextOid(Oid nextOid);
+extern XLogRecPtr LogNextRelFileNumber(RelFileNumber nextrelnumber);
 extern XLogRecPtr XLogRestorePoint(const char *rpName);
 extern void UpdateFullPageWrites(void);
 extern void GetFullPageWriteInfo(XLogRecPtr *RedoRecPtr_p, bool *doPageWrites_p);

src/include/catalog/catalog.h

@@ -38,8 +38,5 @@ extern bool IsPinnedObject(Oid classId, Oid objectId);
 
 extern Oid	GetNewOidWithIndex(Relation relation, Oid indexId,
 							   AttrNumber oidcolumn);
-extern RelFileNumber GetNewRelFileNumber(Oid reltablespace,
-										 Relation pg_class,
-										 char relpersistence);
 
 #endif							/* CATALOG_H */

src/include/catalog/catversion.h

@@ -57,6 +57,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	202209261
+#define CATALOG_VERSION_NO	202209271
 
 #endif

src/include/catalog/pg_class.h

@@ -34,6 +34,13 @@ CATALOG(pg_class,1259,RelationRelationId) BKI_BOOTSTRAP BKI_ROWTYPE_OID(83,Relat
 	/* oid */
 	Oid			oid;
 
+	/* access method; 0 if not a table / index */
+	Oid			relam BKI_DEFAULT(heap) BKI_LOOKUP_OPT(pg_am);
+
+	/* identifier of physical storage file */
+	/* relfilenode == 0 means it is a "mapped" relation, see relmapper.c */
+	int64		relfilenode BKI_DEFAULT(0);
+
 	/* class name */
 	NameData	relname;
 
@@ -49,13 +56,6 @@ CATALOG(pg_class,1259,RelationRelationId) BKI_BOOTSTRAP BKI_ROWTYPE_OID(83,Relat
 	/* class owner */
 	Oid			relowner BKI_DEFAULT(POSTGRES) BKI_LOOKUP(pg_authid);
 
-	/* access method; 0 if not a table / index */
-	Oid			relam BKI_DEFAULT(heap) BKI_LOOKUP_OPT(pg_am);
-
-	/* identifier of physical storage file */
-	/* relfilenode == 0 means it is a "mapped" relation, see relmapper.c */
-	Oid			relfilenode BKI_DEFAULT(0);
-
 	/* identifier of table space for relation (0 means default for database) */
 	Oid			reltablespace BKI_DEFAULT(0) BKI_LOOKUP_OPT(pg_tablespace);
 
@@ -154,7 +154,7 @@ typedef FormData_pg_class *Form_pg_class;
 
 DECLARE_UNIQUE_INDEX_PKEY(pg_class_oid_index, 2662, ClassOidIndexId, on pg_class using btree(oid oid_ops));
 DECLARE_UNIQUE_INDEX(pg_class_relname_nsp_index, 2663, ClassNameNspIndexId, on pg_class using btree(relname name_ops, relnamespace oid_ops));
-DECLARE_INDEX(pg_class_tblspc_relfilenode_index, 3455, ClassTblspcRelfilenodeIndexId, on pg_class using btree(reltablespace oid_ops, relfilenode oid_ops));
+DECLARE_INDEX(pg_class_tblspc_relfilenode_index, 3455, ClassTblspcRelfilenodeIndexId, on pg_class using btree(reltablespace oid_ops, relfilenode int8_ops));
 
 #ifdef EXPOSE_TO_CLIENT_CODE
 

src/include/catalog/pg_control.h

@@ -41,6 +41,7 @@ typedef struct CheckPoint
 								 * timeline (equals ThisTimeLineID otherwise) */
 	bool		fullPageWrites; /* current full_page_writes */
 	FullTransactionId nextXid;	/* next free transaction ID */
+	RelFileNumber nextRelFileNumber;	/* next relfilenumber */
 	Oid			nextOid;		/* next free OID */
 	MultiXactId nextMulti;		/* next free MultiXactId */
 	MultiXactOffset nextMultiOffset;	/* next free MultiXact offset */
@@ -78,6 +79,7 @@ typedef struct CheckPoint
 #define XLOG_FPI						0xB0
 /* 0xC0 is used in Postgres 9.5-11 */
 #define XLOG_OVERWRITE_CONTRECORD		0xD0
+#define XLOG_NEXT_RELFILENUMBER			0xE0
 
 
 /*

src/include/catalog/pg_proc.dat

@@ -7329,11 +7329,11 @@
   proname => 'pg_indexes_size', provolatile => 'v', prorettype => 'int8',
   proargtypes => 'regclass', prosrc => 'pg_indexes_size' },
 { oid => '2999', descr => 'filenode identifier of relation',
-  proname => 'pg_relation_filenode', provolatile => 's', prorettype => 'oid',
+  proname => 'pg_relation_filenode', provolatile => 's', prorettype => 'int8',
   proargtypes => 'regclass', prosrc => 'pg_relation_filenode' },
 { oid => '3454', descr => 'relation OID for filenode and tablespace',
   proname => 'pg_filenode_relation', provolatile => 's',
-  prorettype => 'regclass', proargtypes => 'oid oid',
+  prorettype => 'regclass', proargtypes => 'oid int8',
   prosrc => 'pg_filenode_relation' },
 { oid => '3034', descr => 'file path of relation',
   proname => 'pg_relation_filepath', provolatile => 's', prorettype => 'text',
@@ -11125,15 +11125,15 @@
   prosrc => 'binary_upgrade_set_missing_value' },
 { oid => '4545', descr => 'for use by pg_upgrade',
   proname => 'binary_upgrade_set_next_heap_relfilenode', provolatile => 'v',
-  proparallel => 'u', prorettype => 'void', proargtypes => 'oid',
+  proparallel => 'u', prorettype => 'void', proargtypes => 'int8',
   prosrc => 'binary_upgrade_set_next_heap_relfilenode' },
 { oid => '4546', descr => 'for use by pg_upgrade',
   proname => 'binary_upgrade_set_next_index_relfilenode', provolatile => 'v',
-  proparallel => 'u', prorettype => 'void', proargtypes => 'oid',
+  proparallel => 'u', prorettype => 'void', proargtypes => 'int8',
   prosrc => 'binary_upgrade_set_next_index_relfilenode' },
 { oid => '4547', descr => 'for use by pg_upgrade',
   proname => 'binary_upgrade_set_next_toast_relfilenode', provolatile => 'v',
-  proparallel => 'u', prorettype => 'void', proargtypes => 'oid',
+  proparallel => 'u', prorettype => 'void', proargtypes => 'int8',
   prosrc => 'binary_upgrade_set_next_toast_relfilenode' },
 { oid => '4548', descr => 'for use by pg_upgrade',
   proname => 'binary_upgrade_set_next_pg_tablespace_oid', provolatile => 'v',

src/include/common/relpath.h

@@ -22,10 +22,12 @@
 /*
  * RelFileNumber data type identifies the specific relation file name.
  */
-typedef Oid RelFileNumber;
+typedef uint64 RelFileNumber;
-#define InvalidRelFileNumber		((RelFileNumber) InvalidOid)
+#define InvalidRelFileNumber		((RelFileNumber) 0)
 #define RelFileNumberIsValid(relnumber) \
 				((bool) ((relnumber) != InvalidRelFileNumber))
+#define atorelnumber(x) ((RelFileNumber) strtou64((x), NULL, 10))
+#define MAX_RELFILENUMBER	UINT64CONST(0x00FFFFFFFFFFFFFF)
 
 /*
  * Name of major-version-specific tablespace subdirectories
@@ -35,6 +37,7 @@ typedef Oid RelFileNumber;
 
 /* Characters to allow for an OID in a relation path */
 #define OIDCHARS		10		/* max chars printed by %u */
+#define RELNUMBERCHARS	20		/* max chars printed by UINT64_FORMAT */
 
 /*
  * Stuff for fork names.

src/include/fe_utils/option_utils.h

@@ -22,5 +22,7 @@ extern void handle_help_version_opts(int argc, char *argv[],
 extern bool option_parse_int(const char *optarg, const char *optname,
 							 int min_range, int max_range,
 							 int *result);
+extern bool option_parse_relfilenumber(const char *optarg,
+									   const char *optname);
 
 #endif							/* OPTION_UTILS_H */

src/include/storage/buf_internals.h

@@ -92,29 +92,66 @@ typedef struct buftag
 {
 	Oid			spcOid;			/* tablespace oid */
 	Oid			dbOid;			/* database oid */
-	RelFileNumber relNumber;	/* relation file number */
+
-	ForkNumber	forkNum;		/* fork number */
+	/*
+	 * relForkDetails[] stores the fork number in the high 8 bits of the first
+	 * integer; the remaining 56 bits are used to store the relfilenmber.
+	 * Expanding the relfilenumber to a full 64 bits would require widening
+	 * the BufferTag, which is undesirable for performance reasons. We use
+	 * two 32-bit values here rather than a single 64-bit value to avoid
+	 * padding the struct out to a multiple of 8 bytes.
+	 */
+	uint32		relForkDetails[2];
 	BlockNumber blockNum;		/* blknum relative to begin of reln */
 } BufferTag;
 
+/* High relNumber bits in relForkDetails[0] */
+#define	BUFTAG_RELNUM_HIGH_BITS	24
+
+/* Low relNumber bits in relForkDetails[1] */
+#define	BUFTAG_RELNUM_LOW_BITS	32
+
+/* Mask to fetch high bits of relNumber from relForkDetails[0] */
+#define	BUFTAG_RELNUM_HIGH_MASK	((1U << BUFTAG_RELNUM_HIGH_BITS) - 1)
+
+/* Mask to fetch low bits of relNumber from relForkDetails[1] */
+#define	BUFTAG_RELNUM_LOW_MASK	0XFFFFFFFF
+
 static inline RelFileNumber
 BufTagGetRelNumber(const BufferTag *tag)
 {
-	return tag->relNumber;
+	uint64		relnum;
+
+	relnum = ((uint64) tag->relForkDetails[0]) & BUFTAG_RELNUM_HIGH_MASK;
+	relnum = (relnum << BUFTAG_RELNUM_LOW_BITS) | tag->relForkDetails[1];
+
+	Assert(relnum <= MAX_RELFILENUMBER);
+	return (RelFileNumber) relnum;
 }
 
 static inline ForkNumber
 BufTagGetForkNum(const BufferTag *tag)
 {
-	return tag->forkNum;
+	ForkNumber		ret;
+
+	StaticAssertStmt(MAX_FORKNUM <= INT8_MAX,
+					 "MAX_FORKNUM can't be greater than INT8_MAX");
+
+	ret = (int8) (tag->relForkDetails[0] >> BUFTAG_RELNUM_HIGH_BITS);
+	return ret;
 }
 
 static inline void
 BufTagSetRelForkDetails(BufferTag *tag, RelFileNumber relnumber,
 						ForkNumber forknum)
 {
-	tag->relNumber = relnumber;
+	Assert(relnumber <= MAX_RELFILENUMBER);
-	tag->forkNum = forknum;
+	Assert(forknum <= MAX_FORKNUM);
+
+	tag->relForkDetails[0] = (relnumber >> BUFTAG_RELNUM_LOW_BITS) &
+		BUFTAG_RELNUM_HIGH_MASK;
+	tag->relForkDetails[0] |= (forknum << BUFTAG_RELNUM_HIGH_BITS);
+	tag->relForkDetails[1] = relnumber & BUFTAG_RELNUM_LOW_MASK;
 }
 
 static inline RelFileLocator
@@ -153,9 +190,9 @@ BufferTagsEqual(const BufferTag *tag1, const BufferTag *tag2)
 {
 	return (tag1->spcOid == tag2->spcOid) &&
 		(tag1->dbOid == tag2->dbOid) &&
-		(tag1->relNumber == tag2->relNumber) &&
+		(tag1->relForkDetails[0] == tag2->relForkDetails[0]) &&
-		(tag1->blockNum == tag2->blockNum) &&
+		(tag1->relForkDetails[1] == tag2->relForkDetails[1]) &&
-		(tag1->forkNum == tag2->forkNum);
+		(tag1->blockNum == tag2->blockNum);
 }
 
 static inline bool

src/include/storage/relfilelocator.h

@@ -32,10 +32,11 @@
  * Nonzero dbOid values correspond to pg_database.oid.
  *
  * relNumber identifies the specific relation.  relNumber corresponds to
- * pg_class.relfilenode (NOT pg_class.oid, because we need to be able
+ * pg_class.relfilenode.  Notice that relNumber values are assigned by
- * to assign new physical files to relations in some situations).
+ * GetNewRelFileNumber(), which will only ever assign the same value once
- * Notice that relNumber is only unique within a database in a particular
+ * during the lifetime of a cluster.  However, since CREATE DATABASE duplicates
- * tablespace.
+ * the relfilenumbers of the template database, the values are in practice only
+ * unique within a database, not globally.
  *
  * Note: spcOid must be GLOBALTABLESPACE_OID if and only if dbOid is
  * zero.  We support shared relations only in the "global" tablespace.
@@ -75,6 +76,9 @@ typedef struct RelFileLocatorBackend
 	BackendId	backend;
 } RelFileLocatorBackend;
 
+#define SizeOfRelFileLocatorBackend \
+	(offsetof(RelFileLocatorBackend, backend) + sizeof(BackendId))
+
 #define RelFileLocatorBackendIsTemp(rlocator) \
 	((rlocator).backend != InvalidBackendId)
 

src/test/regress/expected/alter_table.out

@@ -2164,9 +2164,8 @@ select relname,
   c.oid = oldoid as orig_oid,
   case relfilenode
     when 0 then 'none'
-    when c.oid then 'own'
     when oldfilenode then 'orig'
-    else 'OTHER'
+    else 'new'
     end as storage,
   obj_description(c.oid, 'pg_class') as desc
   from pg_class c left join old_oids using (relname)
@@ -2175,10 +2174,10 @@ select relname,
            relname            | orig_oid | storage |     desc      
 ------------------------------+----------+---------+---------------
  at_partitioned               | t        | none    | 
- at_partitioned_0             | t        | own     | 
+ at_partitioned_0             | t        | orig    | 
- at_partitioned_0_id_name_key | t        | own     | child 0 index
+ at_partitioned_0_id_name_key | t        | orig    | child 0 index
- at_partitioned_1             | t        | own     | 
+ at_partitioned_1             | t        | orig    | 
- at_partitioned_1_id_name_key | t        | own     | child 1 index
+ at_partitioned_1_id_name_key | t        | orig    | child 1 index
  at_partitioned_id_name_key   | t        | none    | parent index
 (6 rows)
 
@@ -2198,9 +2197,8 @@ select relname,
   c.oid = oldoid as orig_oid,
   case relfilenode
     when 0 then 'none'
-    when c.oid then 'own'
     when oldfilenode then 'orig'
-    else 'OTHER'
+    else 'new'
     end as storage,
   obj_description(c.oid, 'pg_class') as desc
   from pg_class c left join old_oids using (relname)
@@ -2209,10 +2207,10 @@ select relname,
            relname            | orig_oid | storage |     desc     
 ------------------------------+----------+---------+--------------
  at_partitioned               | t        | none    | 
- at_partitioned_0             | t        | own     | 
+ at_partitioned_0             | t        | orig    | 
- at_partitioned_0_id_name_key | f        | own     | parent index
+ at_partitioned_0_id_name_key | f        | new     | parent index
- at_partitioned_1             | t        | own     | 
+ at_partitioned_1             | t        | orig    | 
- at_partitioned_1_id_name_key | f        | own     | parent index
+ at_partitioned_1_id_name_key | f        | new     | parent index
  at_partitioned_id_name_key   | f        | none    | parent index
 (6 rows)
 
@@ -2560,7 +2558,7 @@ CREATE FUNCTION check_ddl_rewrite(p_tablename regclass, p_ddl text)
 RETURNS boolean
 LANGUAGE plpgsql AS $$
 DECLARE
-    v_relfilenode oid;
+    v_relfilenode int8;
 BEGIN
     v_relfilenode := relfilenode FROM pg_class WHERE oid = p_tablename;
 

src/test/regress/expected/fast_default.out

@@ -3,8 +3,8 @@
 --
 SET search_path = fast_default;
 CREATE SCHEMA fast_default;
-CREATE TABLE m(id OID);
+CREATE TABLE m(id BIGINT);
-INSERT INTO m VALUES (NULL::OID);
+INSERT INTO m VALUES (NULL::BIGINT);
 CREATE FUNCTION set(tabname name) RETURNS VOID
 AS $$
 BEGIN

src/test/regress/expected/oidjoins.out

@@ -74,11 +74,11 @@ NOTICE:  checking pg_type {typcollation} => pg_collation {oid}
 NOTICE:  checking pg_attribute {attrelid} => pg_class {oid}
 NOTICE:  checking pg_attribute {atttypid} => pg_type {oid}
 NOTICE:  checking pg_attribute {attcollation} => pg_collation {oid}
+NOTICE:  checking pg_class {relam} => pg_am {oid}
 NOTICE:  checking pg_class {relnamespace} => pg_namespace {oid}
 NOTICE:  checking pg_class {reltype} => pg_type {oid}
 NOTICE:  checking pg_class {reloftype} => pg_type {oid}
 NOTICE:  checking pg_class {relowner} => pg_authid {oid}
-NOTICE:  checking pg_class {relam} => pg_am {oid}
 NOTICE:  checking pg_class {reltablespace} => pg_tablespace {oid}
 NOTICE:  checking pg_class {reltoastrelid} => pg_class {oid}
 NOTICE:  checking pg_class {relrewrite} => pg_class {oid}

src/test/regress/sql/alter_table.sql

@@ -1478,9 +1478,8 @@ select relname,
   c.oid = oldoid as orig_oid,
   case relfilenode
     when 0 then 'none'
-    when c.oid then 'own'
     when oldfilenode then 'orig'
-    else 'OTHER'
+    else 'new'
     end as storage,
   obj_description(c.oid, 'pg_class') as desc
   from pg_class c left join old_oids using (relname)
@@ -1499,9 +1498,8 @@ select relname,
   c.oid = oldoid as orig_oid,
   case relfilenode
     when 0 then 'none'
-    when c.oid then 'own'
     when oldfilenode then 'orig'
-    else 'OTHER'
+    else 'new'
     end as storage,
   obj_description(c.oid, 'pg_class') as desc
   from pg_class c left join old_oids using (relname)
@@ -1641,7 +1639,7 @@ CREATE FUNCTION check_ddl_rewrite(p_tablename regclass, p_ddl text)
 RETURNS boolean
 LANGUAGE plpgsql AS $$
 DECLARE
-    v_relfilenode oid;
+    v_relfilenode int8;
 BEGIN
     v_relfilenode := relfilenode FROM pg_class WHERE oid = p_tablename;
 

src/test/regress/sql/fast_default.sql

@@ -4,8 +4,8 @@
 
 SET search_path = fast_default;
 CREATE SCHEMA fast_default;
-CREATE TABLE m(id OID);
+CREATE TABLE m(id BIGINT);
-INSERT INTO m VALUES (NULL::OID);
+INSERT INTO m VALUES (NULL::BIGINT);
 
 CREATE FUNCTION set(tabname name) RETURNS VOID
 AS $$