Re: Understanding Datum

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Nick Raj <nickrajjain(at)gmail(dot)com>
Cc: Radosław Smogura <mail(at)smogura(dot)eu>, pgsql-general(at)postgresql(dot)org
Subject: Re: Understanding Datum
Date: 2011-03-23 21:05:42
Message-ID: 4479.1300914342@sss.pgh.pa.us
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Nick Raj <nickrajjain(at)gmail(dot)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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