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

doc/src/sgml/catalogs.sgml

@@ -7657,23 +7657,6 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
       </para></entry>
      </row>
 
-     <row>
-      <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>stxstattarget</structfield> <type>int2</type>
-      </para>
-      <para>
-       <structfield>stxstattarget</structfield> controls the level of detail
-       of statistics accumulated for this statistics object by
-       <link linkend="sql-analyze"><command>ANALYZE</command></link>.
-       A zero value indicates that no statistics should be collected.
-       A negative value says to use the maximum of the statistics targets of
-       the referenced columns, if set, or the system default statistics target.
-       Positive values of <structfield>stxstattarget</structfield>
-       determine the target number of <quote>most common values</quote>
-       to collect.
-      </para></entry>
-     </row>
-
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>stxkeys</structfield> <type>int2vector</type>
@@ -7687,6 +7670,23 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
       </para></entry>
      </row>
 
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>stxstattarget</structfield> <type>int2</type>
+      </para>
+      <para>
+       <structfield>stxstattarget</structfield> controls the level of detail
+       of statistics accumulated for this statistics object by
+       <link linkend="sql-analyze"><command>ANALYZE</command></link>.
+       A zero value indicates that no statistics should be collected.
+       A null value says to use the maximum of the statistics targets of
+       the referenced columns, if set, or the system default statistics target.
+       Positive values of <structfield>stxstattarget</structfield>
+       determine the target number of <quote>most common values</quote>
+       to collect.
+      </para></entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>stxkind</structfield> <type>char[]</type>

doc/src/sgml/ref/alter_statistics.sgml

@@ -26,7 +26,7 @@ PostgreSQL documentation
 ALTER STATISTICS <replaceable class="parameter">name</replaceable> OWNER TO { <replaceable class="parameter">new_owner</replaceable> | CURRENT_ROLE | CURRENT_USER | SESSION_USER }
 ALTER STATISTICS <replaceable class="parameter">name</replaceable> RENAME TO <replaceable class="parameter">new_name</replaceable>
 ALTER STATISTICS <replaceable class="parameter">name</replaceable> SET SCHEMA <replaceable class="parameter">new_schema</replaceable>
-ALTER STATISTICS <replaceable class="parameter">name</replaceable> SET STATISTICS <replaceable class="parameter">new_target</replaceable>
+ALTER STATISTICS <replaceable class="parameter">name</replaceable> SET STATISTICS { <replaceable class="parameter">new_target</replaceable> | DEFAULT }
 </synopsis>
  </refsynopsisdiv>
 
@@ -101,10 +101,11 @@ ALTER STATISTICS <replaceable class="parameter">name</replaceable> SET STATISTIC
        <para>
         The statistic-gathering target for this statistics object for subsequent
         <link linkend="sql-analyze"><command>ANALYZE</command></link> operations.
-        The target can be set in the range 0 to 10000; alternatively, set it
+        The target can be set in the range 0 to 10000.  Set it to
-        to -1 to revert to using the maximum of the statistics target of the
+        <literal>DEFAULT</literal> to revert to using the system default
-        referenced columns, if set, or the system default statistics
+        statistics target (<xref linkend="guc-default-statistics-target"/>).
-        target (<xref linkend="guc-default-statistics-target"/>).
+        (Setting to a value of -1 is an obsolete way spelling to get the same
+        outcome.)
         For more information on the use of statistics by the
         <productname>PostgreSQL</productname> query planner, refer to
         <xref linkend="planner-stats"/>.

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;
@@ -606,10 +606,22 @@ 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;
 
+	/* -1 was used in previous versions for the default setting */
+	if (stmt->stxstattarget && intVal(stmt->stxstattarget) != -1)
+	{
+		newtarget = intVal(stmt->stxstattarget);
+		newtarget_default = false;
+	}
+	else
+		newtarget_default = true;
+
+	if (!newtarget_default)
+	{
 		/* Limit statistics target to a sane range */
-	if (newtarget < -1)
+		if (newtarget < 0)
 		{
 			ereport(ERROR,
 					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
@@ -624,6 +636,7 @@ AlterStatistics(AlterStatsStmt *stmt)
 					 errmsg("lowering statistics target to %d",
 							newtarget)));
 		}
+	}
 
 	/* lookup OID of the statistics object */
 	stxoid = get_statistics_object_oid(stmt->defnames, stmt->missing_ok);
@@ -673,7 +686,10 @@ AlterStatistics(AlterStatsStmt *stmt)
 
 	/* replace the stxstattarget column */
 	repl_repl[Anum_pg_statistic_ext_stxstattarget - 1] = true;
+	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);

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;
@@ -8733,22 +8734,21 @@ 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;
-		/*
-		 * -1 was used in previous versions to represent the default setting
-		 */
-		newtarget = -1;
-	}
 
+	if (!newtarget_default)
+	{
 		/*
 		 * Limit target to a sane range
 		 */
-	if (newtarget < -1)
+		if (newtarget < 0)
 		{
 			ereport(ERROR,
 					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
@@ -8763,6 +8763,7 @@ ATExecSetStatistics(Relation rel, const char *colName, int16 colNum, Node *newVa
 					 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;

src/backend/parser/gram.y

@@ -4610,7 +4610,7 @@ stats_param:	ColId
  *****************************************************************************/
 
 AlterStatsStmt:
-			ALTER STATISTICS any_name SET STATISTICS SignedIconst
+			ALTER STATISTICS any_name SET STATISTICS set_statistics_value
 				{
 					AlterStatsStmt *n = makeNode(AlterStatsStmt);
 
@@ -4619,7 +4619,7 @@ AlterStatsStmt:
 					n->stxstattarget = $6;
 					$$ = (Node *) n;
 				}
-			| ALTER STATISTICS IF_P EXISTS any_name SET STATISTICS SignedIconst
+			| ALTER STATISTICS IF_P EXISTS any_name SET STATISTICS set_statistics_value
 				{
 					AlterStatsStmt *n = makeNode(AlterStatsStmt);
 

src/backend/statistics/extended_stats.c

@@ -454,13 +454,15 @@ fetch_statentries_for_relation(Relation pg_statext, Oid relid)
 		entry->statOid = staForm->oid;
 		entry->schema = get_namespace_name(staForm->stxnamespace);
 		entry->name = pstrdup(NameStr(staForm->stxname));
-		entry->stattarget = staForm->stxstattarget;
 		for (i = 0; i < staForm->stxkeys.dim1; i++)
 		{
 			entry->columns = bms_add_member(entry->columns,
 											staForm->stxkeys.values[i]);
 		}
 
+		datum = SysCacheGetAttr(STATEXTOID, htup, Anum_pg_statistic_ext_stxstattarget, &isnull);
+		entry->stattarget = isnull ? -1 : DatumGetInt16(datum);
+
 		/* decode the stxkind char array into a list of chars */
 		datum = SysCacheGetAttrNotNull(STATEXTOID, htup,
 									   Anum_pg_statistic_ext_stxkind);

src/bin/pg_dump/pg_dump.c

@@ -7580,7 +7580,7 @@ getExtendedStatistics(Archive *fout)
 
 	if (fout->remoteVersion < 130000)
 		appendPQExpBufferStr(query, "SELECT tableoid, oid, stxname, "
-							 "stxnamespace, stxowner, stxrelid, (-1) AS stxstattarget "
+							 "stxnamespace, stxowner, stxrelid, NULL AS stxstattarget "
 							 "FROM pg_catalog.pg_statistic_ext");
 	else
 		appendPQExpBufferStr(query, "SELECT tableoid, oid, stxname, "
@@ -7613,6 +7613,9 @@ getExtendedStatistics(Archive *fout)
 		statsextinfo[i].rolname = getRoleName(PQgetvalue(res, i, i_stxowner));
 		statsextinfo[i].stattable =
 			findTableByOid(atooid(PQgetvalue(res, i, i_stxrelid)));
+		if (PQgetisnull(res, i, i_stattarget))
+			statsextinfo[i].stattarget = -1;
+		else
 			statsextinfo[i].stattarget = atoi(PQgetvalue(res, i, i_stattarget));
 
 		/* Decide whether we want to dump it */
@@ -17062,8 +17065,7 @@ dumpStatisticsExt(Archive *fout, const StatsExtInfo *statsextinfo)
 
 	/*
 	 * We only issue an ALTER STATISTICS statement if the stxstattarget entry
-	 * for this statistics object is non-negative (i.e. it's not the default
+	 * for this statistics object is not the default value.
-	 * value).
 	 */
 	if (statsextinfo->stattarget >= 0)
 	{

src/bin/psql/describe.c

@@ -2804,7 +2804,8 @@ describeOneTableDetails(const char *schemaname,
 									  PQgetvalue(result, i, 1));
 
 					/* Show the stats target if it's not default */
-					if (strcmp(PQgetvalue(result, i, 8), "-1") != 0)
+					if (!PQgetisnull(result, i, 8) &&
+						strcmp(PQgetvalue(result, i, 8), "-1") != 0)
 						appendPQExpBuffer(&buf, "; STATISTICS %s",
 										  PQgetvalue(result, i, 8));
 

src/include/catalog/catversion.h

@@ -57,6 +57,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	202403141
+#define CATALOG_VERSION_NO	202403171
 
 #endif

src/include/catalog/pg_statistic_ext.h

@@ -43,15 +43,15 @@ CATALOG(pg_statistic_ext,3381,StatisticExtRelationId)
 														 * object's namespace */
 
 	Oid			stxowner BKI_LOOKUP(pg_authid); /* statistics object's owner */
-	int16		stxstattarget BKI_DEFAULT(-1);	/* statistics target */
 
 	/*
-	 * variable-length fields start here, but we allow direct access to
+	 * variable-length/nullable fields start here, but we allow direct access
-	 * stxkeys
+	 * to stxkeys
 	 */
 	int2vector	stxkeys BKI_FORCE_NOT_NULL; /* array of column keys */
 
 #ifdef CATALOG_VARLEN
+	int16		stxstattarget BKI_DEFAULT(_null_) BKI_FORCE_NULL;	/* statistics target */
 	char		stxkind[1] BKI_FORCE_NOT_NULL;	/* statistics kinds requested
 												 * to build */
 	pg_node_tree stxexprs;		/* A list of expression trees for stats

src/include/nodes/parsenodes.h

@@ -3269,7 +3269,7 @@ typedef struct AlterStatsStmt
 {
 	NodeTag		type;
 	List	   *defnames;		/* qualified name (list of String) */
-	int			stxstattarget;	/* statistics target */
+	Node	   *stxstattarget;	/* statistics target */
 	bool		missing_ok;		/* skip error if statistics object is missing */
 } AlterStatsStmt;