Revert 56-bit relfilenode change and follow-up commits.

There are still some alignment-related failures in the buildfarm,
which might or might not be able to be fixed quickly, but I've also
just realized that it increased the size of many WAL records by 4 bytes
because a block reference contains a RelFileLocator. The effect of that
hasn't been studied or discussed, so revert for now.

3 files changed, 15 insertions, 59 deletions

diff --git a/src/include/storage/buf_internals.h b/src/include/storage/buf_internals.h
index d4dc9eb3429..406db6be783 100644
--- a/src/include/storage/buf_internals.h
+++ b/src/include/storage/buf_internals.h
@@ -92,66 +92,29 @@ typedef struct buftag
 {
 	Oid			spcOid;			/* tablespace oid */
 	Oid			dbOid;			/* database oid */
-
-	/*
-	 * 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];
+	RelFileNumber relNumber;	/* relation file number */
+	ForkNumber	forkNum;		/* fork number */
 	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)
 {
-	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;
+	return tag->relNumber;
 }
 
 static inline ForkNumber
 BufTagGetForkNum(const BufferTag *tag)
 {
-	ForkNumber		ret;
-
-	StaticAssertStmt(MAX_FORKNUM <= INT8_MAX,
-					 "MAX_FORKNUM can't be greater than INT8_MAX");
-
-	ret = (ForkNumber) (tag->relForkDetails[0] >> BUFTAG_RELNUM_HIGH_BITS);
-	return ret;
+	return tag->forkNum;
 }
 
 static inline void
 BufTagSetRelForkDetails(BufferTag *tag, RelFileNumber relnumber,
 						ForkNumber forknum)
 {
-	Assert(relnumber <= MAX_RELFILENUMBER);
-	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;
+	tag->relNumber = relnumber;
+	tag->forkNum = forknum;
 }
 
 static inline RelFileLocator
@@ -190,9 +153,9 @@ BufferTagsEqual(const BufferTag *tag1, const BufferTag *tag2)
 {
 	return (tag1->spcOid == tag2->spcOid) &&
 		(tag1->dbOid == tag2->dbOid) &&
-		(tag1->relForkDetails[0] == tag2->relForkDetails[0]) &&
-		(tag1->relForkDetails[1] == tag2->relForkDetails[1]) &&
-		(tag1->blockNum == tag2->blockNum);
+		(tag1->relNumber == tag2->relNumber) &&
+		(tag1->blockNum == tag2->blockNum) &&
+		(tag1->forkNum == tag2->forkNum);
 }
 
 static inline bool
diff --git a/src/include/storage/relfilelocator.h b/src/include/storage/relfilelocator.h
index ef904644fa4..10f41f3abb3 100644
--- a/src/include/storage/relfilelocator.h
+++ b/src/include/storage/relfilelocator.h
@@ -32,11 +32,10 @@
  * Nonzero dbOid values correspond to pg_database.oid.
  *
  * relNumber identifies the specific relation.  relNumber corresponds to
- * pg_class.relfilenode.  Notice that relNumber values are assigned by
- * GetNewRelFileNumber(), which will only ever assign the same value once
- * during the lifetime of a cluster.  However, since CREATE DATABASE duplicates
- * the relfilenumbers of the template database, the values are in practice only
- * unique within a database, not globally.
+ * pg_class.relfilenode (NOT pg_class.oid, because we need to be able
+ * to assign new physical files to relations in some situations).
+ * Notice that relNumber is only unique within a database in a particular
+ * tablespace.
  *
  * Note: spcOid must be GLOBALTABLESPACE_OID if and only if dbOid is
  * zero.  We support shared relations only in the "global" tablespace.
@@ -76,9 +75,6 @@ typedef struct RelFileLocatorBackend
 	BackendId	backend;
 } RelFileLocatorBackend;
 
-#define SizeOfRelFileLocatorBackend \
-	(offsetof(RelFileLocatorBackend, backend) + sizeof(BackendId))
-
 #define RelFileLocatorBackendIsTemp(rlocator) \
 	((rlocator).backend != InvalidBackendId)
 
diff --git a/src/include/storage/sinval.h b/src/include/storage/sinval.h
index 4a267be935c..aca0347a3d3 100644
--- a/src/include/storage/sinval.h
+++ b/src/include/storage/sinval.h
@@ -86,14 +86,11 @@ typedef struct
 
 typedef struct
 {
-	/* note: field layout chosen to pack into 20 bytes */
+	/* note: field layout chosen to pack into 16 bytes */
 	int8		id;				/* type field --- must be first */
 	int8		backend_hi;		/* high bits of backend ID, if temprel */
 	uint16		backend_lo;		/* low bits of backend ID, if temprel */
-	Oid			dbOid;
-	Oid			spcOid;
-	uint32		relNumber_hi;	/* avoid 8 byte alignment requirement */
-	uint32		relNumber_lo;
+	RelFileLocator rlocator;	/* spcOid, dbOid, relNumber */
 } SharedInvalSmgrMsg;
 
 #define SHAREDINVALRELMAP_ID	(-4)