From 05d4cbf9b6ba708858984b01ca0fc56d59d4ec7c Mon Sep 17 00:00:00 2001
From: Robert Haas
Date: Tue, 27 Sep 2022 13:25:21 -0400
Subject: 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
---
 src/include/common/relpath.h | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

(limited to 'src/include/common')

diff --git a/src/include/common/relpath.h b/src/include/common/relpath.h
index 4bbd94393c8..2d3b52fe0b8 100644
--- a/src/include/common/relpath.h
+++ b/src/include/common/relpath.h
@@ -22,10 +22,12 @@
 /*
  * RelFileNumber data type identifies the specific relation file name.
  */
-typedef Oid RelFileNumber;
-#define InvalidRelFileNumber		((RelFileNumber) InvalidOid)
+typedef uint64 RelFileNumber;
+#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.
-- 
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