PG_FREE_IF_COPY extraneous in numeric_cmp?
Hi hackers,
I have a question on the code below:
Datum
numeric_cmp(PG_FUNCTION_ARGS)
{
Numeric num1 = PG_GETARG_NUMERIC(0);
Numeric num2 = PG_GETARG_NUMERIC(1);
int result;
result = cmp_numerics(num1, num2);
PG_FREE_IF_COPY(num1, 0);
PG_FREE_IF_COPY(num2, 1);
PG_RETURN_INT32(result);
}
It seems to me that num1 is a copy of fcinfo->arg[0]. It is passed to
the function cmp_numerics(), It's value remains the same after the
call. Also, cmp_numerics() does not have a handle to fcinfo, so it
can't modify fcinfo->arg[0].
Isn't it true that pfree() will never be called by PG_FREE_IF_COPY?
Cheers,
-cktan
CK Tan <cktan@vitessedata.com> writes:
Isn't it true that pfree() will never be called by PG_FREE_IF_COPY?
No. You're forgetting the possibility that PG_GETARG_NUMERIC will
have to de-toast a toasted input. Granted, numerics are seldom
going to be long enough to get compressed or pushed out-of-line;
but that's possible, and what's very possible is that they'll have
a short header.
regards, tom lane
Thanks!
Show quoted text
On Fri, Feb 24, 2023 at 2:16 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
CK Tan <cktan@vitessedata.com> writes:
Isn't it true that pfree() will never be called by PG_FREE_IF_COPY?
No. You're forgetting the possibility that PG_GETARG_NUMERIC will
have to de-toast a toasted input. Granted, numerics are seldom
going to be long enough to get compressed or pushed out-of-line;
but that's possible, and what's very possible is that they'll have
a short header.regards, tom lane