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

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От Bruce Momjian
Тема Re: [HACKERS] I think we need an explicit parsetree node for CAST
Дата
Msg-id 200001160241.VAA27171@candle.pha.pa.us
обсуждение исходный текст
Ответ на I think we need an explicit parsetree node for CAST  (Tom Lane <tgl@sss.pgh.pa.us>)
Ответы Re: [HACKERS] I think we need an explicit parsetree node for CAST  (Tom Lane <tgl@sss.pgh.pa.us>)
Список pgsql-hackers
> 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).

Actually, I think I never made the additional atttypmod changes because
no one had ever reported a problem, and I was confused by that.

--  Bruce Momjian                        |  http://www.op.net/~candle pgman@candle.pha.pa.us               |  (610)
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