Remove Get/SetZenithCurrentClusterSize from Postgres core (#399)

Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>

Author: knizhnik

src/backend/access/transam/xlog.c

@@ -592,12 +592,6 @@ typedef struct XLogCtlData
 	/* neon: copy of startup's RedoStartLSN for walproposer's use */
 	XLogRecPtr	RedoStartLSN;
 
-	/*
-	 * size of a timeline in zenith pageserver.
-	 * used to enforce timeline size limit.
-	 */
-	uint64 		zenithCurrentClusterSize;
-
 	slock_t		info_lck;		/* locks shared variables shown above */
 } XLogCtlData;
 
@@ -6431,28 +6425,6 @@ GetRedoStartLsn(void)
 	return XLogCtl->RedoStartLSN;
 }
 
-
-uint64
-GetZenithCurrentClusterSize(void)
-{
-	uint64 size;
-	SpinLockAcquire(&XLogCtl->info_lck);
-	size = XLogCtl->zenithCurrentClusterSize;
-	SpinLockRelease(&XLogCtl->info_lck);
-
-	return size;
-}
-
-
-void
-SetZenithCurrentClusterSize(uint64 size)
-{
-	SpinLockAcquire(&XLogCtl->info_lck);
-	XLogCtl->zenithCurrentClusterSize = size;
-	SpinLockRelease(&XLogCtl->info_lck);
-}
-
-
 /*
  * GetFlushRecPtr -- Returns the current flush position, ie, the last WAL
  * position known to be fsync'd to disk. This should only be used on a

src/include/access/xlog.h

@@ -270,10 +270,6 @@ extern XLogRecPtr GetLastWrittenLSN(RelFileLocator relfilenode, ForkNumber forkn
 extern void SetRedoStartLsn(XLogRecPtr RedoStartLSN);
 extern XLogRecPtr GetRedoStartLsn(void);
 
-extern void SetZenithCurrentClusterSize(uint64 size);
-extern uint64 GetZenithCurrentClusterSize(void);
-
-
 extern void SetWalWriterSleeping(bool sleeping);
 
 /*