Make vacuum buffer counters 64 bits wide

Using 32 bit counters means they can now realistically wrap around when
vacuuming extremely large tables.  Because they're signed integers,
stats printed by vacuum look very odd when they do.

We'd love to backpatch this, but refrain because the variables are
exported and could cause third-party code to break.

Reviewed-by: Julien Rouhaud, Tom Lane, Michael Paquier
Discussion: https://postgr.es/m/20200131205926.GA16367@alvherre.pgsql

src/backend/access/heap/vacuumlazy.c

@@ -614,10 +614,10 @@ heap_vacuum_rel(Relation onerel, VacuumParams *params,
 							 vacrelstats->new_dead_tuples,
 							 OldestXmin);
 			appendStringInfo(&buf,
-							 _("buffer usage: %d hits, %d misses, %d dirtied\n"),
-							 VacuumPageHit,
-							 VacuumPageMiss,
-							 VacuumPageDirty);
+							 _("buffer usage: %lld hits, %lld misses, %lld dirtied\n"),
+							 (long long) VacuumPageHit,
+							 (long long) VacuumPageMiss,
+							 (long long) VacuumPageDirty);
 			appendStringInfo(&buf, _("avg read rate: %.3f MB/s, avg write rate: %.3f MB/s\n"),
 							 read_rate, write_rate);
 			appendStringInfo(&buf, _("system usage: %s"), pg_rusage_show(&ru0));

src/backend/utils/init/globals.c

@@ -140,9 +140,9 @@ int			VacuumCostPageDirty = 20;
 int			VacuumCostLimit = 200;
 double		VacuumCostDelay = 0;
 
-int			VacuumPageHit = 0;
-int			VacuumPageMiss = 0;
-int			VacuumPageDirty = 0;
+int64		VacuumPageHit = 0;
+int64		VacuumPageMiss = 0;
+int64		VacuumPageDirty = 0;
 
 int			VacuumCostBalance = 0;	/* working state for vacuum */
 bool		VacuumCostActive = false;

src/include/miscadmin.h

@@ -252,9 +252,9 @@ extern int	VacuumCostPageDirty;
 extern int	VacuumCostLimit;
 extern double VacuumCostDelay;
 
-extern int	VacuumPageHit;
-extern int	VacuumPageMiss;
-extern int	VacuumPageDirty;
+extern int64 VacuumPageHit;
+extern int64 VacuumPageMiss;
+extern int64 VacuumPageDirty;
 
 extern int	VacuumCostBalance;
 extern bool VacuumCostActive;