Thread

1. gram.y

   jose' soares <sferac@bo.nettuno.it> — 1998-12-03T12:22:45Z

   Hi all,
   
   I'm trying to make parser recognize SELECTs between parenthesis.
   I need to do this work to have m$access working with PostgreSQL.
   The micro$oft access jet (great wisdom) translates the UNIONs as:
   (SELECT ...) UNION (SELECT ...)
   To have PostgreSQL understand this syntax I edited gram.y
   and I modified the "SelectStmt:" and the "SubUnion:" as:
   
   SelectStmt: opt_left_paren SELECT
                              opt_unique
                              res_target_list2
                              result
                              from_clause
                              where_clause
                              group_clause
                              having_clause
               opt_right_paren
                              union_clause
                              sort_clause
                                   {
                                           SelectStmt *n   = makeNode(SelectStmt);
                                           n->unique       = $3;
                                           n->targetList   = $4;
                                           n->into         = $5;
                                           n->fromClause   = $6;
                                           n->whereClause  = $7;
                                           n->groupClause  = $8;
                                           n->havingClause = $9;
                                           n->unionClause  = $11;
                                           n->sortClause   = $12;
                                           $$ = (Node *)n;
                                   }
                   ;
   
   SubUnion: opt_left_paren SELECT opt_unique res_target_list2
                            from_clause where_clause
                            group_clause having_clause opt_right_paren
                                   {
                                           SelectStmt *n   = makeNode(SelectStmt);
                                           n->unique       = $3;
                                           n->unionall     = FALSE;
                                           n->targetList   = $4;
                                           n->fromClause   = $5;
                                           n->whereClause  = $6;
                                           n->groupClause  = $7;
                                           n->havingClause = $8;
                                           $$ = (Node *)n;
                                   }
                   ;
   
   
   and now with these changes I can specify SELECTs inside () and
   without parenthesis as before, I tried also subselects and seems that
   all works well...but when I tried a select with a function which contains
   parenthesis, like SUM(), VERSION() for example, then it doesn't work anymore.
   I'm not very good programing in C.
   Is there anybody that can help me with this question ?
   Any help would be very appreciated.
   
   EXAMPLES:
   
   (select (2-3)*3);
   ?column?
   --------
         -3
   (1 row)
   
   (select (132-3)*3)  union all ( select ((983+1)/2) );
   ?column?
   --------
        387
        492
   (2 rows)
   
   select (132-3)*3  union all  select ((983+1)/2);
   ?column?
   --------
        387
        492
   (2 rows)
   
   select ename from emp where ename in (
        select ename from emp where ename like 'K%'
        );
   ename
   -----
   KING
   (1 row)
   
   select version();
   ERROR:  parser: parse error at or near "("
   
   -Jose'-
   
   
   
   

2. Re: [HACKERS] gram.y

   Thomas Lockhart <lockhart@alumni.caltech.edu> — 1998-12-06T07:06:04Z

   > I'm trying to make parser recognize SELECTs between parenthesis.
   > I need to do this work to have m$access working with PostgreSQL.
   > The micro$oft access jet (great wisdom) translates the UNIONs as:
   > (SELECT ...) UNION (SELECT ...)
   
   OK, just assume I have mentioned that you should ask M$ to support
   standard syntax. It isn't entirely clear from the BNF definition of
   SQL92 (parens near SELECT are allowed in some places), but I was hard
   pressed to see where this was legal syntax.
   
   > To have PostgreSQL understand this syntax I edited gram.y
   > and I modified the "SelectStmt:" and the "SubUnion:" as:
   > SelectStmt: opt_left_paren SELECT
   <snip>
   
   One problem with this is the parens must of course be balanced, so
   making them individually optional is probably not the right thing to do.
   Just to experiment I tried adding parens on some of the several places
   where selects with unions are allowed, and started running into trouble
   on the second one I tried. I'm guessing that a yacc-based parser will
   run into serious trouble, but I haven't thought of a completely fatal
   example yet.
   
   Also, the way gram.y is currently laid out it would be difficult to
   ensure that all clauses of the UNION are surrounded by parens if one
   clause has those parens. But I think this would be desirable if the
   parens are going to be allowed at all.
   
                         - Tom
   
   

3. Re[2]: [HACKERS] gram.y

   jose' soares <sferac@bo.nettuno.it> — 1998-12-10T13:31:59Z

   Hello Thomas,
   
   domenica, 6 dicembre 98, you wrote:
   
   >> I'm trying to make parser recognize SELECTs between parenthesis.
   >> I need to do this work to have m$access working with PostgreSQL.
   >> The micro$oft access jet (great wisdom) translates the UNIONs as:
   >> (SELECT ...) UNION (SELECT ...)
   
   TGL> OK, just assume I have mentioned that you should ask M$ to support
   TGL> standard syntax. It isn't entirely clear from the BNF definition of
   TGL> SQL92 (parens near SELECT are allowed in some places), but I was hard
   TGL> pressed to see where this was legal syntax.
   
   The problem is: I can't say this syntax is illegal, I can't find
   nothing about it on SQL documentation.
   
   Any way. I think it would be interesting to have parser recognize every
   statement enclosed into parens.
   I have also Informix-SE on my Linux box, I tried statements enclosed
   into parens and Informix understand it.
   
   -Jose'-