Re: Understanding Datum - Mailing list pgsql-general

From Nick Raj
Subject Re: Understanding Datum
Date
Msg-id AANLkTinTBMnBP7Owy=ZBB8aQo+TBSS+YOtjCus6pmP4y@mail.gmail.com
Whole thread Raw
In response to Re: Understanding Datum  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: Understanding Datum  (Pavel Stehule <pavel.stehule@gmail.com>)
Re: Understanding Datum  (rsmogura <rsmogura@softperience.eu>)
List pgsql-general
If Datum contains only the value (not having type specific info.), then
Suppose i want to print the Datum V value (already defined in postgres)
then printf("%??", V);

Because V is assigned by PG_GETARG_POINTER(1);
I don't having the information of type Datum.

How to print the value of Datum in postgres?


On Thu, Mar 24, 2011 at 2:35 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
Nick Raj <nickrajjain@gmail.com> writes:
> In postgres, typedef uintptr_t Datum
> Datum is getting value from PG_GETARG_POINTER(1);
> But, now problem is how would i know the type of PG_GETARG_POINTER(1)
> (postgres internally pass this argument) to figure out datum type?

Datum does not carry any type information, only a value.  Functions are
typically coded to know their input types a priori.  If you want to
write code that is not type-specific then you'd better be passing around
type OIDs as well as values.

                       regards, tom lane

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