Re: [PATCHES] [HACKERS] parser dilemma

[Zoltan Boszormenyi]

Zoltan Boszormenyi írta:

Martijn van Oosterhout írta:

On Thu, Apr 19, 2007 at 11:19:40AM +0200, Zoltan Boszormenyi wrote:

The problem comes from cases like

    colname coltype DEFAULT 5! GENERATED ...

Since b_expr allows postfix operators, it takes one more token of
lookahead than we have to tell if the default expression is "5!"
or "5!GENERATED ...".

ISTM that as long as:

 colname coltype DEFAULT (5!) GENERATED ...

works I don't see why it would be a problem to require the parentheses
in this case. Postfis operators are not going to be that common here I
think.

Have a nice day,

You mean like this one?
------------------------------------------------------------------------
*** gram.y.old  2007-04-20 09:23:16.000000000 +0200
--- gram.y      2007-04-20 09:25:34.000000000 +0200
***************
*** 7550,7557 ****

                               {

--- 7550,7557 ----

                               {

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

This change alone brings 13 reduce/reduce conflicts.

{ $$ = (Node *) makeA_Expr(AEXPR_OP, $2, $1, $3, @2); } | qual_Op b_expr %prec Op { $$ = (Node *) makeA_Expr(AEXPR_OP, $1, NULL, $2, @1); } ! | b_expr qual_Op %prec POSTFIXOP ! { $$ = (Node *) makeA_Expr(AEXPR_OP, $2, $1, NULL, @2); } | b_expr IS DISTINCT FROM b_expr %prec IS $$ = (Node *) makeSimpleA_Expr(AEXPR_DISTINCT, "=", $1, $5, @2); { $$ = (Node *) makeA_Expr(AEXPR_OP, $2, $1, $3, @2); } | qual_Op b_expr %prec Op { $$ = (Node *) makeA_Expr(AEXPR_OP, $1, NULL, $2, @1); } ! | '(' b_expr qual_Op ')' %prec POSTFIXOP ! { $$ = (Node *) makeA_Expr(AEXPR_OP, $3, $2, NULL, @3); } | b_expr IS DISTINCT FROM b_expr %prec IS $$ = (Node *) makeSimpleA_Expr(AEXPR_DISTINCT, "=", $1, $5, @2);

On the other hand, marking GENERATED as %right
solves this issue. I hope it's an acceptable solution.

Best regards,
Zoltán Böszörményi

--
----------------------------------
Zoltán Böszörményi
Cybertec Geschwinde & Schönig GmbH
http://www.postgresql.at/

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