Index SLRUs by 64-bit integers rather than by 32-bit integers

We've had repeated bugs in the area of handling SLRU wraparound in the past,
some of which have caused data loss. Switching to an indexing system for SLRUs
that does not wrap around should allow us to get rid of a whole bunch
of problems and improve the overall reliability of the system.

This particular patch however only changes the indexing and doesn't address
the wraparound per se. This is going to be done in the following patches.

Author: Maxim Orlov, Aleksander Alekseev, Alexander Korotkov, Teodor Sigaev
Author: Nikita Glukhov, Pavel Borisov, Yura Sokolov
Reviewed-by: Jacob Champion, Heikki Linnakangas, Alexander Korotkov
Reviewed-by: Japin Li, Pavel Borisov, Tom Lane, Peter Eisentraut, Andres Freund
Reviewed-by: Andrey Borodin, Dilip Kumar, Aleksander Alekseev
Discussion: https://postgr.es/m/CACG%3DezZe1NQSCnfHOr78AtAZxJZeCvxrts0ygrxYwe%3DpyyjVWA%40mail.gmail.com
Discussion: https://postgr.es/m/CAJ7c6TPDOYBYrnCAeyndkBktO0WG2xSdYduTF0nxq%2BvfkmTF5Q%40mail.gmail.com

5 files changed, 26 insertions, 17 deletions

diff --git a/src/include/access/clog.h b/src/include/access/clog.h
index d99444f073f..8fd99ba670b 100644
--- a/src/include/access/clog.h
+++ b/src/include/access/clog.h
@@ -31,7 +31,7 @@ typedef int XidStatus;
 
 typedef struct xl_clog_truncate
 {
-	int			pageno;
+	int64		pageno;
 	TransactionId oldestXact;
 	Oid			oldestXactDb;
 } xl_clog_truncate;
diff --git a/src/include/access/commit_ts.h b/src/include/access/commit_ts.h
index 5087cdce51e..11fa3a922d9 100644
--- a/src/include/access/commit_ts.h
+++ b/src/include/access/commit_ts.h
@@ -60,7 +60,7 @@ typedef struct xl_commit_ts_set
 
 typedef struct xl_commit_ts_truncate
 {
-	int			pageno;
+	int64		pageno;
 	TransactionId oldestXid;
 } xl_commit_ts_truncate;
 
diff --git a/src/include/access/slru.h b/src/include/access/slru.h
index 552cc19e685..091e2202c95 100644
--- a/src/include/access/slru.h
+++ b/src/include/access/slru.h
@@ -64,7 +64,7 @@ typedef struct SlruSharedData
 	char	  **page_buffer;
 	SlruPageStatus *page_status;
 	bool	   *page_dirty;
-	int		   *page_number;
+	int64	   *page_number;
 	int		   *page_lru_count;
 	LWLockPadded *buffer_locks;
 
@@ -95,7 +95,7 @@ typedef struct SlruSharedData
 	 * this is not critical data, since we use it only to avoid swapping out
 	 * the latest page.
 	 */
-	int			latest_page_number;
+	int64		latest_page_number;
 
 	/* SLRU's index for statistics purposes (might not be unique) */
 	int			slru_stats_idx;
@@ -127,7 +127,15 @@ typedef struct SlruCtlData
 	 * the behavior of this callback has no functional implications.)  Use
 	 * SlruPagePrecedesUnitTests() in SLRUs meeting its criteria.
 	 */
-	bool		(*PagePrecedes) (int, int);
+	bool		(*PagePrecedes) (int64, int64);
+
+	/*
+	 * If true, use long segment filenames formed from lower 48 bits of the
+	 * segment number, e.g. pg_xact/000000001234. Otherwise, use short
+	 * filenames formed from lower 16 bits of the segment number e.g.
+	 * pg_xact/1234.
+	 */
+	bool		long_segment_names;
 
 	/*
 	 * Dir is set during SimpleLruInit and does not change thereafter. Since
@@ -142,11 +150,12 @@ typedef SlruCtlData *SlruCtl;
 extern Size SimpleLruShmemSize(int nslots, int nlsns);
 extern void SimpleLruInit(SlruCtl ctl, const char *name, int nslots, int nlsns,
 						  LWLock *ctllock, const char *subdir, int tranche_id,
-						  SyncRequestHandler sync_handler);
-extern int	SimpleLruZeroPage(SlruCtl ctl, int pageno);
-extern int	SimpleLruReadPage(SlruCtl ctl, int pageno, bool write_ok,
+						  SyncRequestHandler sync_handler,
+						  bool long_segment_names);
+extern int	SimpleLruZeroPage(SlruCtl ctl, int64 pageno);
+extern int	SimpleLruReadPage(SlruCtl ctl, int64 pageno, bool write_ok,
 							  TransactionId xid);
-extern int	SimpleLruReadPage_ReadOnly(SlruCtl ctl, int pageno,
+extern int	SimpleLruReadPage_ReadOnly(SlruCtl ctl, int64 pageno,
 									   TransactionId xid);
 extern void SimpleLruWritePage(SlruCtl ctl, int slotno);
 extern void SimpleLruWriteAll(SlruCtl ctl, bool allow_redirtied);
@@ -155,20 +164,20 @@ extern void SlruPagePrecedesUnitTests(SlruCtl ctl, int per_page);
 #else
 #define SlruPagePrecedesUnitTests(ctl, per_page) do {} while (0)
 #endif
-extern void SimpleLruTruncate(SlruCtl ctl, int cutoffPage);
-extern bool SimpleLruDoesPhysicalPageExist(SlruCtl ctl, int pageno);
+extern void SimpleLruTruncate(SlruCtl ctl, int64 cutoffPage);
+extern bool SimpleLruDoesPhysicalPageExist(SlruCtl ctl, int64 pageno);
 
-typedef bool (*SlruScanCallback) (SlruCtl ctl, char *filename, int segpage,
+typedef bool (*SlruScanCallback) (SlruCtl ctl, char *filename, int64 segpage,
 								  void *data);
 extern bool SlruScanDirectory(SlruCtl ctl, SlruScanCallback callback, void *data);
-extern void SlruDeleteSegment(SlruCtl ctl, int segno);
+extern void SlruDeleteSegment(SlruCtl ctl, int64 segno);
 
 extern int	SlruSyncFileTag(SlruCtl ctl, const FileTag *ftag, char *path);
 
 /* SlruScanDirectory public callbacks */
 extern bool SlruScanDirCbReportPresence(SlruCtl ctl, char *filename,
-										int segpage, void *data);
-extern bool SlruScanDirCbDeleteAll(SlruCtl ctl, char *filename, int segpage,
+										int64 segpage, void *data);
+extern bool SlruScanDirCbDeleteAll(SlruCtl ctl, char *filename, int64 segpage,
 								   void *data);
 
 #endif							/* SLRU_H */
diff --git a/src/include/storage/proc.h b/src/include/storage/proc.h
index ef74f326932..4b259612495 100644
--- a/src/include/storage/proc.h
+++ b/src/include/storage/proc.h
@@ -281,7 +281,7 @@ struct PGPROC
 	TransactionId clogGroupMemberXid;	/* transaction id of clog group member */
 	XidStatus	clogGroupMemberXidStatus;	/* transaction status of clog
 											 * group member */
-	int			clogGroupMemberPage;	/* clog page corresponding to
+	int64		clogGroupMemberPage;	/* clog page corresponding to
 										 * transaction id of clog group member */
 	XLogRecPtr	clogGroupMemberLsn; /* WAL location of commit record for clog
 									 * group member */
diff --git a/src/include/storage/sync.h b/src/include/storage/sync.h
index 963cc82125a..d0af1d902a7 100644
--- a/src/include/storage/sync.h
+++ b/src/include/storage/sync.h
@@ -52,7 +52,7 @@ typedef struct FileTag
 	int16		handler;		/* SyncRequestHandler value, saving space */
 	int16		forknum;		/* ForkNumber, saving space */
 	RelFileLocator rlocator;
-	uint32		segno;
+	uint64		segno;
 } FileTag;
 
 extern void InitSync(void);