From: Bruce Momjian <pgman@candle.pha.pa.us>
Message-Id: <200208280245.g7S2jO803463@candle.pha.pa.us>
Subject: Re: [SQL] LIMIT 1 FOR UPDATE or FOR UPDATE LIMIT 1?
In-Reply-To: <GNELIHDDFBOCMGBFGEFOMEOMCDAA.chriskl@familyhealth.com.au>
To: Christopher Kings-Lynne <chriskl@familyhealth.com.au>
Date: Tue, 27 Aug 2002 22:45:24 -0400 (EDT)
Cc: magnus.enbom@rockstorm.se, Jan Wieck <JanWieck@Yahoo.com>,
	PostgreSQL-development <pgsql-hackers@postgreSQL.org>
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OK, patch attached.  It was actually easier than I thought.  We have to
decide if we are going to remove the old syntax in 7.4.

Regression tests pass.  No doc updates yet.

---------------------------------------------------------------------------

Christopher Kings-Lynne wrote:
> > OK, no one has commented on this, so I guess I am going to have to guess
> > the group's preference.
> >
> > My guess, seeing as very few probably use LIMIT and FOR UPDATE together,
> > is to swap them and document it in the release notes.  Was I correct in
> > my guess?
> 
> I'm sure very few people do it - but are you sure you can't just allow both
> syntaxes?
> 
> Chris
> 
> 
> ---------------------------(end of broadcast)---------------------------
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> 
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> 

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

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Index: src/backend/parser/gram.y
===================================================================
RCS file: /cvsroot/pgsql-server/src/backend/parser/gram.y,v
retrieving revision 2.361
diff -c -c -r2.361 gram.y
*** src/backend/parser/gram.y	27 Aug 2002 04:55:08 -0000	2.361
--- src/backend/parser/gram.y	28 Aug 2002 02:42:16 -0000
***************
*** 208,215 ****
  				func_args_list, func_as, createfunc_opt_list
  				oper_argtypes, RuleActionList, RuleActionMulti,
  				opt_column_list, columnList, opt_name_list,
! 				sort_clause, sortby_list, index_params, index_list,
! 				name_list, from_clause, from_list, opt_array_bounds,
  				qualified_name_list, any_name, any_name_list,
  				any_operator, expr_list, dotted_name, attrs,
  				target_list, update_target_list, insert_column_list,
--- 208,215 ----
  				func_args_list, func_as, createfunc_opt_list
  				oper_argtypes, RuleActionList, RuleActionMulti,
  				opt_column_list, columnList, opt_name_list,
! 				sort_clause, opt_sort_clause, sortby_list, index_params,
! 				index_list,name_list, from_clause, from_list, opt_array_bounds,
  				qualified_name_list, any_name, any_name_list,
  				any_operator, expr_list, dotted_name, attrs,
  				target_list, update_target_list, insert_column_list,
***************
*** 4180,4203 ****
  			| '(' select_with_parens ')'			{ $$ = $2; }
  		;
  
  select_no_parens:
  			simple_select						{ $$ = $1; }
! 			| select_clause sort_clause opt_for_update_clause opt_select_limit
  				{
! 					insertSelectOptions((SelectStmt *) $1, $2, $3,
! 										nth(0, $4), nth(1, $4));
  					$$ = $1;
  				}
! 			| select_clause for_update_clause opt_select_limit
  				{
! 					insertSelectOptions((SelectStmt *) $1, NIL, $2,
! 										nth(0, $3), nth(1, $3));
  					$$ = $1;
  				}
! 			| select_clause select_limit
  				{
! 					insertSelectOptions((SelectStmt *) $1, NIL, NIL,
! 										nth(0, $2), nth(1, $2));
  					$$ = $1;
  				}
  		;
--- 4180,4208 ----
  			| '(' select_with_parens ')'			{ $$ = $2; }
  		;
  
+ /*
+  *	FOR UPDATE may be before or after LIMIT/OFFSET.
+  *	In <=7.2.X, LIMIT/OFFSET had to be after FOR UPDATE
+  *	In >7.3.X, LIMIT/OFFSET will have to be before FOR UPDATE
+  */
  select_no_parens:
  			simple_select						{ $$ = $1; }
! 			| select_clause sort_clause
  				{
! 					insertSelectOptions((SelectStmt *) $1, $2, NIL,
! 										NULL, NULL);
  					$$ = $1;
  				}
! 			| select_clause opt_sort_clause for_update_clause opt_select_limit
  				{
! 					insertSelectOptions((SelectStmt *) $1, $2, $3,
! 										nth(0, $4), nth(1, $4));
  					$$ = $1;
  				}
! 			| select_clause opt_sort_clause select_limit opt_for_update_clause
  				{
! 					insertSelectOptions((SelectStmt *) $1, $2, $4,
! 										nth(0, $3), nth(1, $3));
  					$$ = $1;
  				}
  		;
***************
*** 4332,4337 ****
--- 4337,4347 ----
  			DISTINCT								{ $$ = makeList1(NIL); }
  			| DISTINCT ON '(' expr_list ')'			{ $$ = $4; }
  			| ALL									{ $$ = NIL; }
+ 			| /*EMPTY*/								{ $$ = NIL; }
+ 		;
+ 
+ opt_sort_clause:
+ 			sort_clause								{ $$ = $1;}
  			| /*EMPTY*/								{ $$ = NIL; }
  		;
  

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