Re: Gram.y patches for better parenthesis handling.
| От | The Hermit Hacker |
|---|---|
| Тема | Re: Gram.y patches for better parenthesis handling. |
| Дата | |
| Msg-id | Pine.BSF.4.21.0010281517260.591-100000@thelab.hub.org обсуждение исходный текст |
| Ответ на | Re: Gram.y patches for better parenthesis handling. (Larry Rosenman <ler@lerctr.org>) |
| Список | 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@candle.pha.pa.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@pacbell.net > > > Permanent e-mail forwarder: mailto:Kevin.O'Gorman.64@Alum.Dartmouth.org > > > At school: mailto:kogorman@cs.ucsb.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@candle.pha.pa.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@lerctr.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@hub.org secondary: scrappy@{freebsd|postgresql}.org
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