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Re: Gram.y patches for better parenthesis handling.

From: The Hermit Hacker <scrappy(at)hub(dot)org>
To: Larry Rosenman <ler(at)lerctr(dot)org>
Cc: PGSQL Hackers List <pgsql-hackers(at)hub(dot)org>, pgman(at)candle(dot)pha(dot)pa(dot)us, tgl(at)sss(dot)pgh(dot)pa(dot)us
Subject: Re: Gram.y patches for better parenthesis handling.
Date: 2000-10-28 18:17:38
Message-ID: Pine.BSF.4.21.0010281517260.591-100000@thelab.hub.org (view raw or flat)
Thread:
Lists: pgsql-hackers
On Sat, 28 Oct 2000, Larry Rosenman wrote:

> Err, with Tom's objections, why was this applied?

was going to ask this too ... someone going patch-happy again? :)


> * Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> [001028 11:34]:
> > Applied.   Thanks.
> > 
> > 
> > > Okay, here's my attempt at fixing the problems with parentheses in
> > > subqueries.  It passes the normal 'runcheck' tests, and I've tried
> > > a few simple things like 
> > >   select 1 as foo union (((((select 2))))) order by foo;
> > > 
> > > There are a few things that it doesn't do that have been talked 
> > > about here at least a little:
> > > 
> > > 1) It doesn't allow things like "IN(((select 1)))" -- the select
> > > here has to be at the top level.  This is not new.
> > > 
> > > 2) It does NOT preserve the odd syntax I found when I started looking
> > > at this, where a SELECT statement could begin with parentheses.  Thus,
> > >   (SELECT a from foo) order by a;
> > > fails.
> > > 
> > > I have preserved the ability, used in the regression tests, to
> > > have a single select statement in what appears to be a RuleActionMulti
> > > (but wasn't -- the parens were part of select_clause syntax).
> > > In my version, this is a special form.
> > > 
> > > This may cause some discussion: I have differentiated the two kinds
> > > of RuleActionMulti.  Perhaps nobody knew there were two kinds, because
> > > I don't think the second form appears in the regression tests. This
> > > one uses square brackets instead of parentheses, but originally was
> > > otherwise the same as the one in parentheses.  In this version of
> > > gram.y, the square bracket form treats SELECT statements the same
> > > as the other allowed statements.  As discussed before on this list,
> > > psql cannot make sense out of the results of such a thing, but an
> > > application might.  And I have designs on just such an application.
> > > 
> > > ++ kevin
> > > 
> > > 
> > > 
> > > -- 
> > > Kevin O'Gorman  (805) 650-6274  mailto:kogorman(at)pacbell(dot)net
> > > Permanent e-mail forwarder:  mailto:Kevin.O'Gorman(dot)64(at)Alum(dot)Dartmouth(dot)org
> > > At school: mailto:kogorman(at)cs(dot)ucsb(dot)edu
> > > Web: http://www.cs.ucsb.edu/~kogorman/index.html
> > > Web: http://trixie.kosman.via.ayuda.com/~kevin/index.html
> > > 
> > > "There is a freedom lying beyond circumstance,
> > > derived from the direct intuition that life can
> > > be grounded upon its absorption in what is
> > > changeless amid change" 
> > >    -- Alfred North Whitehead
> > 
> > > --- gram.y.orig	Thu Oct 26 13:13:04 2000
> > > +++ gram.y	Fri Oct 27 17:37:58 2000
> > > @@ -124,14 +124,15 @@
> > >  		DropGroupStmt, DropPLangStmt, DropSchemaStmt, DropStmt, DropTrigStmt,
> > >  		DropUserStmt, DropdbStmt, ExplainStmt, ExtendStmt, FetchStmt,
> > >  		GrantStmt, IndexStmt, InsertStmt, ListenStmt, LoadStmt, LockStmt,
> > > -		NotifyStmt, OptimizableStmt, ProcedureStmt, ReindexStmt,
> > > +		NotifyStmt, OptimizableStmt, ProcedureStmt
> > > +		QualifiedSelectStmt, ReindexStmt,
> > >  		RemoveAggrStmt, RemoveFuncStmt, RemoveOperStmt, RemoveStmt,
> > >  		RenameStmt, RevokeStmt, RuleActionStmt, RuleActionStmtOrEmpty,
> > >  		RuleStmt, SelectStmt, SetSessionStmt, TransactionStmt, TruncateStmt,
> > >  		UnlistenStmt, UpdateStmt, VacuumStmt, VariableResetStmt,
> > >  		VariableSetStmt, VariableShowStmt, ViewStmt
> > >  
> > > -%type <node>	select_clause, select_subclause
> > > +%type <node>	subquery, simple_select, select_head, set_select
> > >  
> > >  %type <list>	SessionList
> > >  %type <node>	SessionClause
> > > @@ -174,19 +175,20 @@
> > >  		result, OptTempTableName, relation_name_list, OptTableElementList,
> > >  		OptUnder, OptInherit, definition, opt_distinct,
> > >  		opt_with, func_args, func_args_list, func_as,
> > > -		oper_argtypes, RuleActionList, RuleActionMulti,
> > > +		oper_argtypes, RuleActionList, RuleActionMulti, 
> > > +		RuleActionOrSelectMulti, RuleActions, RuleActionBracket,
> > >  		opt_column_list, columnList, opt_va_list, va_list,
> > >  		sort_clause, sortby_list, index_params, index_list, name_list,
> > >  		from_clause, from_list, opt_array_bounds,
> > >  		expr_list, attrs, target_list, update_target_list,
> > >  		def_list, opt_indirection, group_clause, TriggerFuncArgs,
> > > -		opt_select_limit
> > > +		opt_select_limit, select_limit
> > >  
> > >  %type <typnam>	func_arg, func_return, aggr_argtype
> > >  
> > >  %type <boolean>	opt_arg, TriggerForOpt, TriggerForType, OptTemp
> > >  
> > > -%type <list>	for_update_clause, update_list
> > > +%type <list>	opt_for_update_clause, for_update_clause, update_list
> > >  %type <boolean>	opt_all
> > >  %type <boolean>	opt_table
> > >  %type <boolean>	opt_chain, opt_trans
> > > @@ -2689,7 +2691,7 @@
> > >  RuleStmt:  CREATE RULE name AS
> > >  		   { QueryIsRule=TRUE; }
> > >  		   ON event TO event_object where_clause
> > > -		   DO opt_instead RuleActionList
> > > +		   DO opt_instead RuleActions
> > >  				{
> > >  					RuleStmt *n = makeNode(RuleStmt);
> > >  					n->rulename = $3;
> > > @@ -2702,17 +2704,42 @@
> > >  				}
> > >  		;
> > >  
> > > -RuleActionList:  NOTHING				{ $$ = NIL; }
> > > -		| SelectStmt					{ $$ = makeList1($1); }
> > > -		| RuleActionStmt				{ $$ = makeList1($1); }
> > > -		| '[' RuleActionMulti ']'		{ $$ = $2; }
> > > -		| '(' RuleActionMulti ')'		{ $$ = $2; } 
> > > +RuleActions:  NOTHING				{ $$ = NIL; }
> > > +		| RuleActionStmt			{ $$ = makeList1($1); }
> > > +		| SelectStmt				{ $$ = makeList1($1); }
> > > +		| RuleActionList
> > > +		| RuleActionBracket
> > > +		;
> > > +
> > > +/* LEGACY: Version 7.0 did not like SELECT statements in these lists,
> > > + * but because of an oddity in the syntax for select_clause, allowed
> > > + * certain forms like "DO INSTEAD (select 1)", and this is used in
> > > + * the regression tests.
> > > + * Here, we're allowing just one SELECT in parentheses, to preserve
> > > + * any such expectations, and make the regression tests work.
> > > + *               ++ KO'G
> > > + */
> > > +RuleActionList:		'(' RuleActionMulti ')'		{ $$ = $2; } 
> > > +		| '(' SelectStmt ')'	{ $$ = makeList1($2); }
> > > +		;
> > > +
> > > +/* An undocumented feature, bracketed lists are allowed to contain
> > > + * SELECT statements on the same basis as the others.  Before this,
> > > + * they were the same as parenthesized lists, and did not allow
> > > + * SelectStmts.  Anybody know why they were here originally?  Or if
> > > + * they're in the regression tests at all?
> > > + *               ++ KO'G
> > > + */
> > > +RuleActionBracket:	'[' RuleActionOrSelectMulti ']'		{ $$ = $2; } 
> > >  		;
> > >  
> > >  /* the thrashing around here is to discard "empty" statements... */
> > >  RuleActionMulti:  RuleActionMulti ';' RuleActionStmtOrEmpty
> > >  				{ if ($3 != (Node *) NULL)
> > > -					$$ = lappend($1, $3);
> > > +					if ($1 != NIL)
> > > +						$$ = lappend($1, $3);
> > > +					else
> > > +						$$ = makeList1($3);
> > >  				  else
> > >  					$$ = $1;
> > >  				}
> > > @@ -2724,6 +2751,31 @@
> > >  				}
> > >  		;
> > >  
> > > +RuleActionOrSelectMulti: RuleActionOrSelectMulti ';' RuleActionStmtOrEmpty
> > > +				{ if ($3 != (Node *) NULL)
> > > +					if ($1 != NIL)
> > > +						$$ = lappend($1, $3);
> > > +					else
> > > +						$$ = makeList1($3);
> > > +				  else
> > > +					$$ = $1;
> > > +				}
> > > +		| RuleActionOrSelectMulti ';' SelectStmt
> > > +				{ if ($1 != NIL)
> > > +						$$ = lappend($1, $3);
> > > +				  else
> > > +						$$ = makeList1($3);
> > > +				}
> > > +		| RuleActionStmtOrEmpty
> > > +				{ if ($1 != (Node *) NULL)
> > > +					$$ = makeList1($1);
> > > +				  else
> > > +					$$ = NIL;
> > > +				}
> > > +		| SelectStmt		{ $$ = makeList1($1); }
> > > +		;
> > > +
> > > +
> > >  RuleActionStmt:	InsertStmt
> > >  		| UpdateStmt
> > >  		| DeleteStmt
> > > @@ -3289,7 +3341,12 @@
> > >   * However, this is not checked by the grammar; parse analysis must check it.
> > >   */
> > >  
> > > -SelectStmt:	  select_clause sort_clause for_update_clause opt_select_limit
> > > +SelectStmt:	QualifiedSelectStmt
> > > +		| select_head
> > > +		;
> > > +
> > > +QualifiedSelectStmt:
> > > +		  select_head sort_clause opt_for_update_clause opt_select_limit
> > >  			{
> > >  				SelectStmt *n = findLeftmostSelect($1);
> > >  
> > > @@ -3299,34 +3356,35 @@
> > >  				n->limitCount = nth(1, $4);
> > >  				$$ = $1;
> > >  			}
> > > -		;
> > > -
> > > -/* This rule parses Select statements that can appear within set operations,
> > > - * including UNION, INTERSECT and EXCEPT.  '(' and ')' can be used to specify
> > > - * the ordering of the set operations.  Without '(' and ')' we want the
> > > - * operations to be ordered per the precedence specs at the head of this file.
> > > - *
> > > - * Since parentheses around SELECTs also appear in the expression grammar,
> > > - * there is a parse ambiguity if parentheses are allowed at the top level of a
> > > - * select_clause: are the parens part of the expression or part of the select?
> > > - * We separate select_clause into two levels to resolve this: select_clause
> > > - * can have top-level parentheses, select_subclause cannot.
> > > - *
> > > - * Note that sort clauses cannot be included at this level --- a sort clause
> > > - * can only appear at the end of the complete Select, and it will be handled
> > > - * by the topmost SelectStmt rule.  Likewise FOR UPDATE and LIMIT.
> > > - */
> > > -select_clause: '(' select_subclause ')'
> > > +		| select_head for_update_clause opt_select_limit
> > >  			{
> > > -				$$ = $2; 
> > > +				SelectStmt *n = findLeftmostSelect($1);
> > > +
> > > +				n->sortClause = NULL;
> > > +				n->forUpdate = $2;
> > > +				n->limitOffset = nth(0, $3);
> > > +				n->limitCount = nth(1, $3);
> > > +				$$ = $1;
> > >  			}
> > > -		| select_subclause
> > > +		| select_head select_limit
> > >  			{
> > > -				$$ = $1; 
> > > +				SelectStmt *n = findLeftmostSelect($1);
> > > +
> > > +				n->sortClause = NULL;
> > > +				n->forUpdate = NULL;
> > > +				n->limitOffset = nth(0, $2);
> > > +				n->limitCount = nth(1, $2);
> > > +				$$ = $1;
> > >  			}
> > >  		;
> > >  
> > > -select_subclause: SELECT opt_distinct target_list
> > > +subquery:	'(' subquery ')'			{ $$ = $2; }
> > > +		| '(' QualifiedSelectStmt ')'	{ $$ = $2; }
> > > +		| '(' set_select ')'			{ $$ = $2; }
> > > +		| simple_select					{ $$ = $1; }
> > > +		;
> > > +
> > > +simple_select: SELECT opt_distinct target_list
> > >  			 result from_clause where_clause
> > >  			 group_clause having_clause
> > >  				{
> > > @@ -3341,7 +3399,13 @@
> > >  					n->havingClause = $8;
> > >  					$$ = (Node *)n;
> > >  				}
> > > -		| select_clause UNION opt_all select_clause
> > > +		;
> > > +
> > > +select_head: simple_select			{ $$ = $1; }
> > > +		|	set_select				{ $$ = $1; }
> > > +		;
> > > +
> > > +set_select: select_head UNION opt_all subquery
> > >  			{	
> > >  				SetOperationStmt *n = makeNode(SetOperationStmt);
> > >  				n->op = SETOP_UNION;
> > > @@ -3350,7 +3414,7 @@
> > >  				n->rarg = $4;
> > >  				$$ = (Node *) n;
> > >  			}
> > > -		| select_clause INTERSECT opt_all select_clause
> > > +		| select_head INTERSECT opt_all subquery
> > >  			{
> > >  				SetOperationStmt *n = makeNode(SetOperationStmt);
> > >  				n->op = SETOP_INTERSECT;
> > > @@ -3359,7 +3423,7 @@
> > >  				n->rarg = $4;
> > >  				$$ = (Node *) n;
> > >  			}
> > > -		| select_clause EXCEPT opt_all select_clause
> > > +		| select_head EXCEPT opt_all subquery
> > >  			{
> > >  				SetOperationStmt *n = makeNode(SetOperationStmt);
> > >  				n->op = SETOP_EXCEPT;
> > > @@ -3424,7 +3488,6 @@
> > >  		;
> > >  
> > >  sort_clause:  ORDER BY sortby_list				{ $$ = $3; }
> > > -		| /*EMPTY*/								{ $$ = NIL; }
> > >  		;
> > >  
> > >  sortby_list:  sortby							{ $$ = makeList1($1); }
> > > @@ -3446,7 +3509,7 @@
> > >  		;
> > >  
> > >  
> > > -opt_select_limit:	LIMIT select_limit_value ',' select_offset_value
> > > +select_limit:	LIMIT select_limit_value ',' select_offset_value
> > >  			{ $$ = makeList2($4, $2); }
> > >  		| LIMIT select_limit_value OFFSET select_offset_value
> > >  			{ $$ = makeList2($4, $2); }
> > > @@ -3456,6 +3519,9 @@
> > >  			{ $$ = makeList2($2, $4); }
> > >  		| OFFSET select_offset_value
> > >  			{ $$ = makeList2($2, NULL); }
> > > +		;
> > > +
> > > +opt_select_limit: select_limit	{ $$ = $1; }
> > >  		| /* EMPTY */
> > >  			{ $$ = makeList2(NULL, NULL); }
> > >  		;
> > > @@ -3555,6 +3621,9 @@
> > >  
> > >  for_update_clause:  FOR UPDATE update_list		{ $$ = $3; }
> > >  		| FOR READ ONLY							{ $$ = NULL; }
> > > +		;
> > > +
> > > +opt_for_update_clause:	for_update_clause		{ $$ = $1; }
> > >  		| /* EMPTY */							{ $$ = NULL; }
> > >  		;
> > >  
> > > @@ -3598,7 +3667,7 @@
> > >  					$1->name = $2;
> > >  					$$ = (Node *) $1;
> > >  				}
> > > -		| '(' select_subclause ')' alias_clause
> > > +		| '(' SelectStmt ')' alias_clause
> > >  				{
> > >  					RangeSubselect *n = makeNode(RangeSubselect);
> > >  					n->subquery = $2;
> > > @@ -4134,7 +4203,7 @@
> > >   * Define row_descriptor to allow yacc to break the reduce/reduce conflict
> > >   *  with singleton expressions.
> > >   */
> > > -row_expr: '(' row_descriptor ')' IN '(' select_subclause ')'
> > > +row_expr: '(' row_descriptor ')' IN '(' SelectStmt ')'
> > >  				{
> > >  					SubLink *n = makeNode(SubLink);
> > >  					n->lefthand = $2;
> > > @@ -4144,7 +4213,7 @@
> > >  					n->subselect = $6;
> > >  					$$ = (Node *)n;
> > >  				}
> > > -		| '(' row_descriptor ')' NOT IN '(' select_subclause ')'
> > > +		| '(' row_descriptor ')' NOT IN '(' SelectStmt ')'
> > >  				{
> > >  					SubLink *n = makeNode(SubLink);
> > >  					n->lefthand = $2;
> > > @@ -4154,7 +4223,7 @@
> > >  					n->subselect = $7;
> > >  					$$ = (Node *)n;
> > >  				}
> > > -		| '(' row_descriptor ')' all_Op sub_type '(' select_subclause ')'
> > > +		| '(' row_descriptor ')' all_Op sub_type '(' SelectStmt ')'
> > >  				{
> > >  					SubLink *n = makeNode(SubLink);
> > >  					n->lefthand = $2;
> > > @@ -4167,7 +4236,7 @@
> > >  					n->subselect = $7;
> > >  					$$ = (Node *)n;
> > >  				}
> > > -		| '(' row_descriptor ')' all_Op '(' select_subclause ')'
> > > +		| '(' row_descriptor ')' all_Op '(' SelectStmt ')'
> > >  				{
> > >  					SubLink *n = makeNode(SubLink);
> > >  					n->lefthand = $2;
> > > @@ -4498,7 +4567,7 @@
> > >  						$$ = n;
> > >  					}
> > >  				}
> > > -		| a_expr all_Op sub_type '(' select_subclause ')'
> > > +		| a_expr all_Op sub_type '(' SelectStmt ')'
> > >  				{
> > >  					SubLink *n = makeNode(SubLink);
> > >  					n->lefthand = makeList1($1);
> > > @@ -4894,7 +4963,7 @@
> > >  					n->agg_distinct = FALSE;
> > >  					$$ = (Node *)n;
> > >  				}
> > > -		| '(' select_subclause ')'
> > > +		| '(' SelectStmt ')'
> > >  				{
> > >  					SubLink *n = makeNode(SubLink);
> > >  					n->lefthand = NIL;
> > > @@ -4904,7 +4973,7 @@
> > >  					n->subselect = $2;
> > >  					$$ = (Node *)n;
> > >  				}
> > > -		| EXISTS '(' select_subclause ')'
> > > +		| EXISTS '(' SelectStmt ')'
> > >  				{
> > >  					SubLink *n = makeNode(SubLink);
> > >  					n->lefthand = NIL;
> > > @@ -5003,7 +5072,7 @@
> > >  				{ $$ = $1; }
> > >  		;
> > >  
> > > -in_expr:  select_subclause
> > > +in_expr:  SelectStmt
> > >  				{
> > >  					SubLink *n = makeNode(SubLink);
> > >  					n->subselect = $1;
> > 
> > 
> > -- 
> >   Bruce Momjian                        |  http://candle.pha.pa.us
> >   pgman(at)candle(dot)pha(dot)pa(dot)us               |  (610) 853-3000
> >   +  If your life is a hard drive,     |  830 Blythe Avenue
> >   +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026
> -- 
> Larry Rosenman                      http://www.lerctr.org/~ler
> Phone: +1 972-414-9812 (voice) Internet: ler(at)lerctr(dot)org
> US Mail: 1905 Steamboat Springs Drive, Garland, TX 75044-6749
> 
> 

Marc G. Fournier                   ICQ#7615664               IRC Nick: Scrappy
Systems Administrator @ hub.org 
primary: scrappy(at)hub(dot)org           secondary: scrappy(at){freebsd|postgresql}.org 


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