Обсуждение: Help with gram.y (UNDER)

Can someone give be a bit of help with gram.y to get this UNDER syntax
right? I did what I though was the obvious  syntax, but it no longer
accepts a plain create table after this change...

OptUnder: UNDER relation_name_list     { $$ = $2; }       | /*EMPTY*/       { $$ = NIL; } ;



CreateStmt:  CREATE OptTemp TABLE relation_name OptUnder '('
OptTableElementList ')' OptInherit        {                   /*etc */        }    ;

The full patch is here...
ftp://ftp.tech.com.au/pub/diff.x

It seems like bison is confused by having that '(' just after an
optional syntax (UNION). If I place something after OptUnder (USING just
to pick a token), then everything works fine (except of course the
spurious USING becomes part of the syntax).

Does the '(' have some kind of second-class status as a token that would
cause this wierdness?

Chris Bitmead wrote:
> 
> Can someone give be a bit of help with gram.y to get this UNDER syntax
> right? I did what I though was the obvious  syntax, but it no longer
> accepts a plain create table after this change...
> 
> OptUnder: UNDER relation_name_list      { $$ = $2; }
>         | /*EMPTY*/       { $$ = NIL; }
>         ;
> 
> CreateStmt:  CREATE OptTemp TABLE relation_name OptUnder '('
> OptTableElementList ')' OptInherit
>                         {
>                         /*etc */
>                         }
>                 ;
> 
> The full patch is here...
> ftp://ftp.tech.com.au/pub/diff.x

Chris Bitmead wrote:
> 
> It seems like bison is confused by having that '(' just after an
> optional syntax (UNION). 

I mean the optional UNDER

> If I place something after OptUnder (USING just

I mean USING;

i.e. CreateStmt:  CREATE OptTemp TABLE relation_name OptUnder USING  '('
OptTableElementList ')' OptInherit

This will accept "CREATE TABLE foo USING (aa text);"

but this...

CreateStmt:  CREATE OptTemp TABLE relation_name OptUnder '('
OptTableElementList ')' OptInherit

won't accept "CREATE TABLE foo (aa text);"

> to pick a token), then everything works fine (except of course the
> spurious USING becomes part of the syntax).
> 
> Does the '(' have some kind of second-class status as a token that would
> cause this wierdness?
> 
> Chris Bitmead wrote:
> >
> > Can someone give be a bit of help with gram.y to get this UNDER syntax
> > right? I did what I though was the obvious  syntax, but it no longer
> > accepts a plain create table after this change...
> >
> > OptUnder: UNDER relation_name_list      { $$ = $2; }
> >         | /*EMPTY*/       { $$ = NIL; }
> >         ;
> >
> > CreateStmt:  CREATE OptTemp TABLE relation_name OptUnder '('
> > OptTableElementList ')' OptInherit
> >                         {
> >                         /*etc */
> >                         }
> >                 ;
> >
> > The full patch is here...
> > ftp://ftp.tech.com.au/pub/diff.x

Chris Bitmead <chris@bitmead.com> writes:
> Does the '(' have some kind of second-class status as a token that would
> cause this wierdness?

No ... very bizarre.  I think you must be introducing some kind of
ambiguity into the grammar, but I can't quite see what.  Are you
getting any sort of warnings out of bison?

Might be worth turning on the logfile option (forget if it's -v or -l)
and looking at the interpreted productions just to make sure bison
is reading things the same way you thought you wrote them.
        regards, tom lane