[Peter Eisentraut <peter.eisentraut@enterprisedb.com>]

There are a number of rules like this in the grammar:

opt_foo: FOO
         | /*EMPTY*/
;

And there are some like this:

opt_foo: FOO         {}
         | /*EMPTY*/  {}
;

and some even like this:

%type <node> opt_foo

opt_foo: FOO         { $$ = NULL; }
         | /*EMPTY*/  { $$ = NULL; }
;

(I mean here specifically those rules where FOO is a noise word and the 
actions are the same in each branch.)

It's obviously confusing to have multiple different styles to do the 
same thing.  And these extra rules (including the empty ones) also end 
up in the output, so they create more work down the line.

The attached patch cleans this up to make them all look like the first 
style.

Attachments:

0001-Clean-up-optional-rules-in-grammar.patch (text/plain, 5.2K) download
From 49ca423b136e65d162ede1b906930e22de4e5f8e Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <peter@eisentraut.org>
Date: Wed, 11 Nov 2020 10:04:48 +0100
Subject: [PATCH] Clean up optional rules in grammar

Various rules for optional keywords contained unnecessary rules and
type declarations.  Remove those, thus making the output a tiny bit
smaller.
---
 src/backend/parser/gram.y | 80 +++++++++++++++++++--------------------
 1 file changed, 40 insertions(+), 40 deletions(-)

diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 95e256883b..398ba9c7d3 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -389,7 +389,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 				OptTableElementList TableElementList OptInherit definition
 				OptTypedTableElementList TypedTableElementList
 				reloptions opt_reloptions
-				OptWith distinct_clause opt_all_clause opt_definition func_args func_args_list
+				OptWith distinct_clause opt_definition func_args func_args_list
 				func_args_with_defaults func_args_with_defaults_list
 				aggr_args aggr_args_list
 				func_as createfunc_opt_list alterfunc_opt_list
@@ -446,7 +446,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	locked_rels_list
 %type <boolean>	all_or_distinct
 
-%type <node>	join_outer join_qual
+%type <node>	join_qual
 %type <jtype>	join_type
 
 %type <list>	extract_list overlay_list position_list
@@ -461,7 +461,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 %type <boolean> copy_from opt_program
 
-%type <ival>	opt_column event cursor_options opt_hold opt_set_data
+%type <ival>	event cursor_options opt_hold opt_set_data
 %type <objtype>	object_type_any_name object_type_name object_type_name_on_any_name
 				drop_type_name
 
@@ -992,9 +992,9 @@ CreateRoleStmt:
 		;
 
 
-opt_with:	WITH									{}
-			| WITH_LA								{}
-			| /*EMPTY*/								{}
+opt_with:	WITH
+			| WITH_LA
+			| /*EMPTY*/
 		;
 
 /*
@@ -3127,8 +3127,8 @@ copy_delimiter:
 		;
 
 opt_using:
-			USING									{}
-			| /*EMPTY*/								{}
+			USING
+			| /*EMPTY*/
 		;
 
 /* new COPY option syntax */
@@ -4319,8 +4319,8 @@ SeqOptElem: AS SimpleTypename
 				}
 		;
 
-opt_by:		BY				{}
-			| /* empty */	{}
+opt_by:		BY
+			| /* empty */
 	  ;
 
 NumericOnly:
@@ -4406,8 +4406,8 @@ opt_validator:
 		;
 
 opt_procedural:
-			PROCEDURAL								{}
-			| /*EMPTY*/								{}
+			PROCEDURAL
+			| /*EMPTY*/
 		;
 
 /*****************************************************************************
@@ -5366,8 +5366,8 @@ TriggerForSpec:
 		;
 
 TriggerForOptEach:
-			EACH									{}
-			| /*EMPTY*/								{}
+			EACH
+			| /*EMPTY*/
 		;
 
 TriggerForType:
@@ -6707,12 +6707,12 @@ fetch_args:	cursor_name
 				}
 		;
 
-from_in:	FROM									{}
-			| IN_P									{}
+from_in:	FROM
+			| IN_P
 		;
 
-opt_from_in:	from_in								{}
-			| /* EMPTY */							{}
+opt_from_in:	from_in
+			| /* EMPTY */
 		;
 
 
@@ -8836,8 +8836,8 @@ RenameStmt: ALTER AGGREGATE aggregate_with_argtypes RENAME TO name
 				}
 		;
 
-opt_column: COLUMN									{ $$ = COLUMN; }
-			| /*EMPTY*/								{ $$ = 0; }
+opt_column: COLUMN
+			| /*EMPTY*/
 		;
 
 opt_set_data: SET DATA_P							{ $$ = 1; }
@@ -9859,9 +9859,9 @@ TransactionStmt:
 				}
 		;
 
-opt_transaction:	WORK							{}
-			| TRANSACTION							{}
-			| /*EMPTY*/								{}
+opt_transaction:	WORK
+			| TRANSACTION
+			| /*EMPTY*/
 		;
 
 transaction_mode_item:
@@ -10066,8 +10066,8 @@ createdb_opt_name:
  *	Though the equals sign doesn't match other WITH options, pg_dump uses
  *	equals for backward compatibility, and it doesn't seem worth removing it.
  */
-opt_equal:	'='										{}
-			| /*EMPTY*/								{}
+opt_equal:	'='
+			| /*EMPTY*/
 		;
 
 
@@ -10285,8 +10285,8 @@ AlterDomainStmt:
 				}
 			;
 
-opt_as:		AS										{}
-			| /* EMPTY */							{}
+opt_as:		AS
+			| /* EMPTY */
 		;
 
 
@@ -10372,8 +10372,8 @@ AlterTSConfigurationStmt:
 		;
 
 /* Use this if TIME or ORDINALITY after WITH should be taken as an identifier */
-any_with:	WITH									{}
-			| WITH_LA								{}
+any_with:	WITH
+			| WITH_LA
 		;
 
 
@@ -10520,8 +10520,8 @@ vac_analyze_option_list:
 		;
 
 analyze_keyword:
-			ANALYZE									{}
-			| ANALYSE /* British */					{}
+			ANALYZE
+			| ANALYSE /* British */
 		;
 
 vac_analyze_option_elem:
@@ -11462,8 +11462,8 @@ OptTempTableName:
 				}
 		;
 
-opt_table:	TABLE									{}
-			| /*EMPTY*/								{}
+opt_table:	TABLE
+			| /*EMPTY*/
 		;
 
 all_or_distinct:
@@ -11481,8 +11481,8 @@ distinct_clause:
 		;
 
 opt_all_clause:
-			ALL										{ $$ = NIL;}
-			| /*EMPTY*/								{ $$ = NIL; }
+			ALL
+			| /*EMPTY*/
 		;
 
 opt_sort_clause:
@@ -12086,15 +12086,15 @@ func_alias_clause:
 				}
 		;
 
-join_type:	FULL join_outer							{ $$ = JOIN_FULL; }
-			| LEFT join_outer						{ $$ = JOIN_LEFT; }
-			| RIGHT join_outer						{ $$ = JOIN_RIGHT; }
+join_type:	FULL opt_outer							{ $$ = JOIN_FULL; }
+			| LEFT opt_outer						{ $$ = JOIN_LEFT; }
+			| RIGHT opt_outer						{ $$ = JOIN_RIGHT; }
 			| INNER_P								{ $$ = JOIN_INNER; }
 		;
 
 /* OUTER is just noise... */
-join_outer: OUTER_P									{ $$ = NULL; }
-			| /*EMPTY*/								{ $$ = NULL; }
+opt_outer: OUTER_P
+			| /*EMPTY*/
 		;
 
 /* JOIN qualification clauses
-- 
2.29.1