Re: [HACKERS] I think we need an explicit parsetree node for CAST

> These particular cases can be fixed with a one-line patch, I think,
> because there is storage in an A_Const node to hold a reference to
> a Typename, which includes typmod.  parse_expr.c is just forgetting
> to pass the typmod to parser_typecast().
> 
> BUT: there isn't any equally simple patch when the value being casted
> is not a constant.  For instance
> 
>     select field1 :: numeric(7,2) from table1;
> 
> cannot work properly now, because gram.y transforms it into
> 
>     select numeric(field1) from table;
> 
> which (a) drops the typmod and (b) bypasses all of the intelligence
> that should be used to determine how to coerce the type.
> 
> What I think we need is to add a new parsetree node type that explicitly
> represents a CAST operator, and then modify parse_expr.c to transform
> that node type into an appropriate function call (or, perhaps, nothing
> at all if the source value is already the right type).

I have on the TODO list, and once considered adding more passing around
of atttypmod in the parser to keep such information.  Maybe I shoud do
that first to see what happens and what gets fixed.

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