Make stxstattarget nullable

To match attstattarget change (commit 4f622503d6d).  The logic inside
CreateStatistics() is clarified a bit compared to that previous patch,
and so here we also update ATExecSetStatistics() to match.

Reviewed-by: Tomas Vondra <tomas.vondra@enterprisedb.com>
Discussion: https://www.postgresql.org/message-id/flat/4da8d211-d54d-44b9-9847-f2a9f1184c76@eisentraut.org

2 files changed, 55 insertions, 38 deletions

diff --git a/src/backend/commands/statscmds.c b/src/backend/commands/statscmds.c
index a855f750c75..5f49479832d 100644
--- a/src/backend/commands/statscmds.c
+++ b/src/backend/commands/statscmds.c
@@ -495,9 +495,9 @@ CreateStatistics(CreateStatsStmt *stmt)
 	values[Anum_pg_statistic_ext_stxrelid - 1] = ObjectIdGetDatum(relid);
 	values[Anum_pg_statistic_ext_stxname - 1] = NameGetDatum(&stxname);
 	values[Anum_pg_statistic_ext_stxnamespace - 1] = ObjectIdGetDatum(namespaceId);
-	values[Anum_pg_statistic_ext_stxstattarget - 1] = Int16GetDatum(-1);
 	values[Anum_pg_statistic_ext_stxowner - 1] = ObjectIdGetDatum(stxowner);
 	values[Anum_pg_statistic_ext_stxkeys - 1] = PointerGetDatum(stxkeys);
+	nulls[Anum_pg_statistic_ext_stxstattarget - 1] = true;
 	values[Anum_pg_statistic_ext_stxkind - 1] = PointerGetDatum(stxkind);
 
 	values[Anum_pg_statistic_ext_stxexprs - 1] = exprsDatum;
@@ -606,23 +606,36 @@ AlterStatistics(AlterStatsStmt *stmt)
 	bool		repl_null[Natts_pg_statistic_ext];
 	bool		repl_repl[Natts_pg_statistic_ext];
 	ObjectAddress address;
-	int			newtarget = stmt->stxstattarget;
+	int			newtarget;
+	bool		newtarget_default;
 
-	/* Limit statistics target to a sane range */
-	if (newtarget < -1)
+	/* -1 was used in previous versions for the default setting */
+	if (stmt->stxstattarget && intVal(stmt->stxstattarget) != -1)
 	{
-		ereport(ERROR,
-				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("statistics target %d is too low",
-						newtarget)));
+		newtarget = intVal(stmt->stxstattarget);
+		newtarget_default = false;
 	}
-	else if (newtarget > MAX_STATISTICS_TARGET)
+	else
+		newtarget_default = true;
+
+	if (!newtarget_default)
 	{
-		newtarget = MAX_STATISTICS_TARGET;
-		ereport(WARNING,
-				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("lowering statistics target to %d",
-						newtarget)));
+		/* Limit statistics target to a sane range */
+		if (newtarget < 0)
+		{
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("statistics target %d is too low",
+							newtarget)));
+		}
+		else if (newtarget > MAX_STATISTICS_TARGET)
+		{
+			newtarget = MAX_STATISTICS_TARGET;
+			ereport(WARNING,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("lowering statistics target to %d",
+							newtarget)));
+		}
 	}
 
 	/* lookup OID of the statistics object */
@@ -673,7 +686,10 @@ AlterStatistics(AlterStatsStmt *stmt)
 
 	/* replace the stxstattarget column */
 	repl_repl[Anum_pg_statistic_ext_stxstattarget - 1] = true;
-	repl_val[Anum_pg_statistic_ext_stxstattarget - 1] = Int16GetDatum(newtarget);
+	if (!newtarget_default)
+		repl_val[Anum_pg_statistic_ext_stxstattarget - 1] = Int16GetDatum(newtarget);
+	else
+		repl_null[Anum_pg_statistic_ext_stxstattarget - 1] = true;
 
 	newtup = heap_modify_tuple(oldtup, RelationGetDescr(rel),
 							   repl_val, repl_null, repl_repl);
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 2470265561a..ae6719329e7 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -8712,6 +8712,7 @@ static ObjectAddress
 ATExecSetStatistics(Relation rel, const char *colName, int16 colNum, Node *newValue, LOCKMODE lockmode)
 {
 	int			newtarget;
+	bool		newtarget_default;
 	Relation	attrelation;
 	HeapTuple	tuple,
 				newtuple;
@@ -8733,35 +8734,35 @@ ATExecSetStatistics(Relation rel, const char *colName, int16 colNum, Node *newVa
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 				 errmsg("cannot refer to non-index column by number")));
 
-	if (newValue)
+	/* -1 was used in previous versions for the default setting */
+	if (newValue && intVal(newValue) != -1)
 	{
 		newtarget = intVal(newValue);
+		newtarget_default = false;
 	}
 	else
+		newtarget_default = true;
+
+	if (!newtarget_default)
 	{
 		/*
-		 * -1 was used in previous versions to represent the default setting
+		 * Limit target to a sane range
 		 */
-		newtarget = -1;
-	}
-
-	/*
-	 * Limit target to a sane range
-	 */
-	if (newtarget < -1)
-	{
-		ereport(ERROR,
-				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("statistics target %d is too low",
-						newtarget)));
-	}
-	else if (newtarget > MAX_STATISTICS_TARGET)
-	{
-		newtarget = MAX_STATISTICS_TARGET;
-		ereport(WARNING,
-				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("lowering statistics target to %d",
-						newtarget)));
+		if (newtarget < 0)
+		{
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("statistics target %d is too low",
+							newtarget)));
+		}
+		else if (newtarget > MAX_STATISTICS_TARGET)
+		{
+			newtarget = MAX_STATISTICS_TARGET;
+			ereport(WARNING,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("lowering statistics target to %d",
+							newtarget)));
+		}
 	}
 
 	attrelation = table_open(AttributeRelationId, RowExclusiveLock);
@@ -8815,7 +8816,7 @@ ATExecSetStatistics(Relation rel, const char *colName, int16 colNum, Node *newVa
 	/* Build new tuple. */
 	memset(repl_null, false, sizeof(repl_null));
 	memset(repl_repl, false, sizeof(repl_repl));
-	if (newtarget != -1)
+	if (!newtarget_default)
 		repl_val[Anum_pg_attribute_attstattarget - 1] = newtarget;
 	else
 		repl_null[Anum_pg_attribute_attstattarget - 1] = true;