Add macro for maximum statistics target

The number of places where 10000 was hardcoded had grown a bit beyond
the comfort level.  Introduce a macro MAX_STATISTICS_TARGET instead.

Reviewed-by: Tomas Vondra <tomas.vondra@enterprisedb.com>
Discussion: https://www.postgresql.org/message-id/flat/d6069765-5971-04d3-c10d-e4f7b2e9c459%40eisentraut.org

Author: petere

src/backend/commands/statscmds.c

@@ -619,9 +619,9 @@ AlterStatistics(AlterStatsStmt *stmt)
 				 errmsg("statistics target %d is too low",
 						newtarget)));
 	}
-	else if (newtarget > 10000)
+	else if (newtarget > MAX_STATISTICS_TARGET)
 	{
-		newtarget = 10000;
+		newtarget = MAX_STATISTICS_TARGET;
 		ereport(WARNING,
 				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 				 errmsg("lowering statistics target to %d",

src/backend/commands/tablecmds.c

@@ -61,6 +61,7 @@
 #include "commands/trigger.h"
 #include "commands/typecmds.h"
 #include "commands/user.h"
+#include "commands/vacuum.h"
 #include "executor/executor.h"
 #include "foreign/fdwapi.h"
 #include "foreign/foreign.h"
@@ -8180,9 +8181,9 @@ ATExecSetStatistics(Relation rel, const char *colName, int16 colNum, Node *newVa
 				 errmsg("statistics target %d is too low",
 						newtarget)));
 	}
-	else if (newtarget > 10000)
+	else if (newtarget > MAX_STATISTICS_TARGET)
 	{
-		newtarget = 10000;
+		newtarget = MAX_STATISTICS_TARGET;
 		ereport(WARNING,
 				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 				 errmsg("lowering statistics target to %d",

src/backend/statistics/extended_stats.c

@@ -379,7 +379,7 @@ statext_compute_stattarget(int stattarget, int nattrs, VacAttrStats **stats)
 		stattarget = default_statistics_target;
 
 	/* As this point we should have a valid statistics target. */
-	Assert((stattarget >= 0) && (stattarget <= 10000));
+	Assert((stattarget >= 0) && (stattarget <= MAX_STATISTICS_TARGET));
 
 	return stattarget;
 }

src/backend/utils/misc/guc_tables.c

@@ -2035,7 +2035,7 @@ struct config_int ConfigureNamesInt[] =
 						 "column-specific target set via ALTER TABLE SET STATISTICS.")
 		},
 		&default_statistics_target,
-		100, 1, 10000,
+		100, 1, MAX_STATISTICS_TARGET,
 		NULL, NULL, NULL
 	},
 	{

src/include/catalog/pg_attribute.h

@@ -165,7 +165,7 @@ CATALOG(pg_attribute,1249,AttributeRelationId) BKI_BOOTSTRAP BKI_ROWTYPE_OID(75,
 	 * that no value has been explicitly set for this column, so ANALYZE
 	 * should use the default setting.
 	 *
-	 * int16 is sufficient because the max value is currently 10000.
+	 * int16 is sufficient for the current max value (MAX_STATISTICS_TARGET).
 	 */
 	int16		attstattarget BKI_DEFAULT(-1);
 

src/include/commands/vacuum.h

@@ -305,6 +305,13 @@ extern PGDLLIMPORT int vacuum_multixact_freeze_table_age;
 extern PGDLLIMPORT int vacuum_failsafe_age;
 extern PGDLLIMPORT int vacuum_multixact_failsafe_age;
 
+/*
+ * Maximum value for default_statistics_target and per-column statistics
+ * targets.  This is fairly arbitrary, mainly to prevent users from creating
+ * unreasonably large statistics that the system cannot handle well.
+ */
+#define MAX_STATISTICS_TARGET 10000
+
 /* Variables for cost-based parallel vacuum */
 extern PGDLLIMPORT pg_atomic_uint32 *VacuumSharedCostBalance;
 extern PGDLLIMPORT pg_atomic_uint32 *VacuumActiveNWorkers;

src/include/statistics/statistics.h

@@ -66,8 +66,8 @@ typedef struct MVDependencies
 #define STATS_MCV_MAGIC			0xE1A651C2	/* marks serialized bytea */
 #define STATS_MCV_TYPE_BASIC	1	/* basic MCV list type */
 
-/* max items in MCV list (should be equal to max default_statistics_target) */
-#define STATS_MCVLIST_MAX_ITEMS        10000
+/* max items in MCV list */
+#define STATS_MCVLIST_MAX_ITEMS        MAX_STATISTICS_TARGET
 
 /*
  * Multivariate MCV (most-common value) lists