Small code simplification

Apply GETSTRUCT() once instead of doing it repeatedly in the same
function.  This simplifies the notation and makes the function's
structure more similar to the surrounding ones.

Discussion: https://www.postgresql.org/message-id/flat/a368248e-69e4-40be-9c07-6c3b5880b0a6@eisentraut.org

Author: petere

src/backend/commands/tablecmds.c

@@ -7736,6 +7736,7 @@ ATExecSetNotNull(AlteredTableInfo *tab, Relation rel,
 				 const char *colName, LOCKMODE lockmode)
 {
 	HeapTuple	tuple;
+	Form_pg_attribute attTup;
 	AttrNumber	attnum;
 	Relation	attr_rel;
 	ObjectAddress address;
@@ -7753,7 +7754,8 @@ ATExecSetNotNull(AlteredTableInfo *tab, Relation rel,
 				 errmsg("column \"%s\" of relation \"%s\" does not exist",
 						colName, RelationGetRelationName(rel))));
 
-	attnum = ((Form_pg_attribute) GETSTRUCT(tuple))->attnum;
+	attTup = (Form_pg_attribute) GETSTRUCT(tuple);
+	attnum = attTup->attnum;
 
 	/* Prevent them from altering a system attribute */
 	if (attnum <= 0)
@@ -7765,9 +7767,9 @@ ATExecSetNotNull(AlteredTableInfo *tab, Relation rel,
 	/*
 	 * Okay, actually perform the catalog change ... if needed
 	 */
-	if (!((Form_pg_attribute) GETSTRUCT(tuple))->attnotnull)
+	if (!attTup->attnotnull)
 	{
-		((Form_pg_attribute) GETSTRUCT(tuple))->attnotnull = true;
+		attTup->attnotnull = true;
 
 		CatalogTupleUpdate(attr_rel, &tuple->t_self, tuple);
 
@@ -7777,8 +7779,7 @@ ATExecSetNotNull(AlteredTableInfo *tab, Relation rel,
 		 * this then we can skip that.  We needn't bother looking if we've
 		 * already found that we must verify some other not-null constraint.
 		 */
-		if (!tab->verify_new_notnull &&
-			!NotNullImpliedByRelConstraints(rel, (Form_pg_attribute) GETSTRUCT(tuple)))
+		if (!tab->verify_new_notnull && !NotNullImpliedByRelConstraints(rel, attTup))
 		{
 			/* Tell Phase 3 it needs to test the constraint */
 			tab->verify_new_notnull = true;