Push attidentity and attgenerated handling into BuildDescForRelation()

Previously, this was handled by the callers separately, but it can be
trivially moved into BuildDescForRelation() so that it is handled in a
central place.

Reviewed-by: Alvaro Herrera <alvherre@alvh.no-ip.org>
Discussion: https://www.postgresql.org/message-id/flat/52a125e4-ff9a-95f5-9f61-b87cf447e4da@eisentraut.org

src/backend/access/common/tupdesc.c

@@ -856,6 +856,8 @@ BuildDescForRelation(const List *columns)
 		has_not_null |= entry->is_not_null;
 		att->attislocal = entry->is_local;
 		att->attinhcount = entry->inhcount;
+		att->attidentity = entry->identity;
+		att->attgenerated = entry->generated;
 	}
 
 	if (has_not_null)

src/backend/commands/tablecmds.c

@@ -941,8 +941,6 @@ DefineRelation(CreateStmt *stmt, char relkind, Oid ownerId,
 			attr->atthasdef = true;
 		}
 
-		attr->attidentity = colDef->identity;
-		attr->attgenerated = colDef->generated;
 		attr->attcompression = GetAttributeCompression(attr->atttypid, colDef->compression);
 		if (colDef->storage_name)
 			attr->attstorage = GetAttributeStorage(attr->atttypid, colDef->storage_name);