Re: [HACKERS] parser enhancement request for 6.5

Thomas Lockhart wrote:

> There is currently a single shift/reduce conflict in  gram.y, and I'm
> suprised to find that it is *not* due to the "NULL_P '=' a_expr" line.
> I'm planning on touching gram.y to hunt down the shift/reduce conflict
> (from previous work I think it in Stefan's "parens around selects"
> mods), and I'll look at the NULL_P issue again also.

    No - not the parens.

    Looking  at  the  y.output  (produced with -v) I see that the
    conflict is at state 266  when  in  the  SelectStmt  the  FOR
    keyword  of FOR UPDATE has been seen.  The SelectStmt is also
    used in CursorStmt.

    The  rule  cursor_clause  in   CursorStmt   results   in   an
    elog(ERROR)   telling   that   cursors  for  update  are  not
    supported. But in fact a

        DECLARE x1 CURSOR FOR SELECT * FROM x FOR UPDATE OF x;

    doesn't  throw  an  error.  So   it   is   the   CursorStmt's
    cursor_clause  that  is  currently unreachable in the parser.
    Instead the SelectStmt's for_update_clause has already  eaten
    up the FOR UPDATE.


Jan

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