parser: centralize common auxiliary productions

Things like "opt_name" can well be shared by various commands rather
than there being multiple definitions of the same thing.  Rename these
productions and move them to appear together in gram.y, which may
improve chances of reuse in the future.

Discussion: https://postgr.es/m/20220721174212.cmitjpuimx6ssyyj@alvherre.pgsql

Author: alvherre

src/backend/parser/gram.y

@@ -334,6 +334,11 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 				simple_select values_clause
 				PLpgSQL_Expr PLAssignStmt
 
+%type <str>			opt_single_name
+%type <list>		opt_qualified_name
+%type <boolean> 	opt_concurrently
+%type <dbehavior>	opt_drop_behavior
+
 %type <node>	alter_column_default opclass_item opclass_drop alter_using
 %type <ival>	add_drop opt_asc_desc opt_nulls_order
 
@@ -343,8 +348,6 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>    alter_identity_column_option_list
 %type <defelt>  alter_identity_column_option
 
-%type <dbehavior>	opt_drop_behavior
-
 %type <list>	createdb_opt_list createdb_opt_items copy_opt_list
 				transaction_mode_list
 				create_extension_opt_list alter_extension_opt_list
@@ -371,7 +374,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <str>		foreign_server_version opt_foreign_server_version
 %type <str>		opt_in_database
 
-%type <str>		OptSchemaName parameter_name
+%type <str>		parameter_name
 %type <list>	OptSchemaEltList parameter_name_list
 
 %type <chr>		am_type
@@ -392,10 +395,10 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <str>		copy_file_name
 				access_method_clause attr_name
 				table_access_method_clause name cursor_name file_name
-				opt_index_name cluster_index_specification
+				cluster_index_specification
 
 %type <list>	func_name handler_name qual_Op qual_all_Op subquery_Op
-				opt_class opt_inline_handler opt_validator validator_clause
+				opt_inline_handler opt_validator validator_clause
 				opt_collate
 
 %type <range>	qualified_name insert_target OptConstrFromTable
@@ -435,7 +438,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 				oper_argtypes RuleActionList RuleActionMulti
 				opt_column_list columnList opt_name_list
 				sort_clause opt_sort_clause sortby_list index_params
-				opt_stats_name stats_params
+				stats_params
 				opt_include opt_c_include index_including_params
 				name_list role_list from_clause from_list opt_array_bounds
 				qualified_name_list any_name any_name_list type_name_list
@@ -495,7 +498,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <str>		unicode_normal_form
 
 %type <boolean> opt_instead
-%type <boolean> opt_unique opt_concurrently opt_verbose opt_full
+%type <boolean> opt_unique opt_verbose opt_full
 %type <boolean> opt_freeze opt_analyze opt_default opt_recheck
 %type <defelt>	opt_binary copy_delimiter
 
@@ -1180,6 +1183,30 @@ stmt:
 				{ $$ = NULL; }
 		;
 
+/*
+ * Generic supporting productions for DDL
+ */
+opt_single_name:
+			ColId							{ $$ = $1; }
+			| /* EMPTY */					{ $$ = NULL; }
+		;
+
+opt_qualified_name:
+			any_name						{ $$ = $1; }
+			| /*EMPTY*/						{ $$ = NIL; }
+		;
+
+opt_concurrently:
+			CONCURRENTLY					{ $$ = true; }
+			| /*EMPTY*/						{ $$ = false; }
+		;
+
+opt_drop_behavior:
+			CASCADE							{ $$ = DROP_CASCADE; }
+			| RESTRICT						{ $$ = DROP_RESTRICT; }
+			| /* EMPTY */					{ $$ = DROP_RESTRICT; /* default */ }
+		;
+
 /*****************************************************************************
  *
  * CALL statement
@@ -1554,7 +1581,7 @@ add_drop:	ADD_P									{ $$ = +1; }
  *****************************************************************************/
 
 CreateSchemaStmt:
-			CREATE SCHEMA OptSchemaName AUTHORIZATION RoleSpec OptSchemaEltList
+			CREATE SCHEMA opt_single_name AUTHORIZATION RoleSpec OptSchemaEltList
 				{
 					CreateSchemaStmt *n = makeNode(CreateSchemaStmt);
 
@@ -1576,7 +1603,7 @@ CreateSchemaStmt:
 					n->if_not_exists = false;
 					$$ = (Node *) n;
 				}
-			| CREATE SCHEMA IF_P NOT EXISTS OptSchemaName AUTHORIZATION RoleSpec OptSchemaEltList
+			| CREATE SCHEMA IF_P NOT EXISTS opt_single_name AUTHORIZATION RoleSpec OptSchemaEltList
 				{
 					CreateSchemaStmt *n = makeNode(CreateSchemaStmt);
 
@@ -1610,11 +1637,6 @@ CreateSchemaStmt:
 				}
 		;
 
-OptSchemaName:
-			ColId									{ $$ = $1; }
-			| /* EMPTY */							{ $$ = NULL; }
-		;
-
 OptSchemaEltList:
 			OptSchemaEltList schema_stmt
 				{
@@ -2995,12 +3017,6 @@ alter_column_default:
 			| DROP DEFAULT				{ $$ = NULL; }
 		;
 
-opt_drop_behavior:
-			CASCADE						{ $$ = DROP_CASCADE; }
-			| RESTRICT					{ $$ = DROP_RESTRICT; }
-			| /* EMPTY */				{ $$ = DROP_RESTRICT; /* default */ }
-		;
-
 opt_collate_clause:
 			COLLATE any_name
 				{
@@ -4467,7 +4483,7 @@ part_params:	part_elem						{ $$ = list_make1($1); }
 			| part_params ',' part_elem			{ $$ = lappend($1, $3); }
 		;
 
-part_elem: ColId opt_collate opt_class
+part_elem: ColId opt_collate opt_qualified_name
 				{
 					PartitionElem *n = makeNode(PartitionElem);
 
@@ -4478,7 +4494,7 @@ part_elem: ColId opt_collate opt_class
 					n->location = @1;
 					$$ = n;
 				}
-			| func_expr_windowless opt_collate opt_class
+			| func_expr_windowless opt_collate opt_qualified_name
 				{
 					PartitionElem *n = makeNode(PartitionElem);
 
@@ -4489,7 +4505,7 @@ part_elem: ColId opt_collate opt_class
 					n->location = @1;
 					$$ = n;
 				}
-			| '(' a_expr ')' opt_collate opt_class
+			| '(' a_expr ')' opt_collate opt_qualified_name
 				{
 					PartitionElem *n = makeNode(PartitionElem);
 
@@ -4543,10 +4559,12 @@ ExistingIndex:   USING INDEX name					{ $$ = $3; }
  * but the grammar accepts it and then we'll throw FEATURE_NOT_SUPPORTED
  * errors as necessary at execution.
  *
+ * Statistics name is optional unless IF NOT EXISTS is specified.
+ *
  *****************************************************************************/
 
 CreateStatsStmt:
-			CREATE STATISTICS opt_stats_name
+			CREATE STATISTICS opt_qualified_name
 			opt_name_list ON stats_params FROM from_list
 				{
 					CreateStatsStmt *n = makeNode(CreateStatsStmt);
@@ -4574,12 +4592,6 @@ CreateStatsStmt:
 				}
 			;
 
-/* Statistics name is optional unless IF NOT EXISTS is specified */
-opt_stats_name:
-			any_name								{ $$ = $1; }
-			| /*EMPTY*/								{ $$ = NULL; }
-		;
-
 /*
  * Statistics attributes can be either simple column references, or arbitrary
  * expressions in parens.  For compatibility with index attributes permitted
@@ -7987,7 +7999,7 @@ defacl_privilege_target:
  * willing to make TABLESPACE a fully reserved word.
  *****************************************************************************/
 
-IndexStmt:	CREATE opt_unique INDEX opt_concurrently opt_index_name
+IndexStmt:	CREATE opt_unique INDEX opt_concurrently opt_single_name
 			ON relation_expr access_method_clause '(' index_params ')'
 			opt_include opt_unique_null_treatment opt_reloptions OptTableSpace where_clause
 				{
@@ -8058,16 +8070,6 @@ opt_unique:
 			| /*EMPTY*/								{ $$ = false; }
 		;
 
-opt_concurrently:
-			CONCURRENTLY							{ $$ = true; }
-			| /*EMPTY*/								{ $$ = false; }
-		;
-
-opt_index_name:
-			name									{ $$ = $1; }
-			| /*EMPTY*/								{ $$ = NULL; }
-		;
-
 access_method_clause:
 			USING name								{ $$ = $2; }
 			| /*EMPTY*/								{ $$ = DEFAULT_INDEX_TYPE; }
@@ -8079,7 +8081,7 @@ index_params:	index_elem							{ $$ = list_make1($1); }
 
 
 index_elem_options:
-	opt_collate opt_class opt_asc_desc opt_nulls_order
+	opt_collate opt_qualified_name opt_asc_desc opt_nulls_order
 		{
 			$$ = makeNode(IndexElem);
 			$$->name = NULL;
@@ -8139,9 +8141,6 @@ opt_collate: COLLATE any_name						{ $$ = $2; }
 			| /*EMPTY*/								{ $$ = NIL; }
 		;
 
-opt_class:	any_name								{ $$ = $1; }
-			| /*EMPTY*/								{ $$ = NIL; }
-		;
 
 opt_asc_desc: ASC							{ $$ = SORTBY_ASC; }
 			| DESC							{ $$ = SORTBY_DESC; }