DETOAST Datum

On Mon, May 16, 2011 at 3:41 AM, Nick Raj <nickrajjain@gmail.com> wrote:

When i called my function, it gives NDBOX to be null
On debugging, i found out ,FunctionInvokeCall invokes fmgr_oldstyle
function, for getting argument

if (fnextra->arg_toastable[i])    //this returns false, not able to get
arguments
            fcinfo->arg[i] =
PointerGetDatum(PG_DETOAST_DATUM(fcinfo->arg[i]));
    }

"How to get arguments toastable??" and even my table pg_class.reltoastrelid
entry is zero.

It's pretty hard to guess what's going wrong here from the information
you've provided. But reltoastid should not be 0 if you're using a
variable-length data type. It's not exactly clear what you've done
wrong though. Are you sure that the type is defined properly, as a
variable-length type?

Can i have to tell explicitly to toast?

No, you don't have to tell it that.

If i commented that if conditions then, it got stuck below:

struct varlena *
pg_detoast_datum(struct varlena * datum)
{
    if (VARATT_IS_EXTENDED(datum))      //My code get stuck here
        return heap_tuple_untoast_attr(datum);
    else
        return datum;
}

Can anyone tell me what VARATT_IS_EXTENDED(datum) mean?

VARATT_IS_EXTENDED() returns true for datums that can be detoasted,
because they are (1) they are stored out-of-line in the TOAST table,
(2) compressed, or (3) unaligned, using a 1-byte header. See
src/include/postgres.h. But I seriously doubt that you need to debug
pg_detoast_datum(). If you're getting a failure there, it's because
something wasn't done right much earlier on in the process.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

Robert Haas <robertmhaas@gmail.com> writes:

On Mon, May 16, 2011 at 3:41 AM, Nick Raj <nickrajjain@gmail.com> wrote:

"How to get arguments toastable??" and even my table pg_class.reltoastrelid
entry is zero.

It's pretty hard to guess what's going wrong here from the information
you've provided. But reltoastid should not be 0 if you're using a
variable-length data type.

It could be if the type is not marked toastable (ie, has storage class
PLAIN, which I think is the default even for varlena types).

But in any case I suspect that 90% of the problem here is an incorrect
declaration of the *function* not the type. We haven't seen the C
function declaration, nor the SQL CREATE FUNCTION command, but if it's
going through fmgr_oldstyle then there isn't a PG_FUNCTION_INFO_V1
marker, which maybe is the problem.

regards, tom lane

On Mon, May 16, 2011 at 7:52 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:

Robert Haas <robertmhaas@gmail.com> writes:

On Mon, May 16, 2011 at 3:41 AM, Nick Raj <nickrajjain@gmail.com> wrote:

"How to get arguments toastable??" and even my table

pg_class.reltoastrelid

entry is zero.

It's pretty hard to guess what's going wrong here from the information
you've provided. But reltoastid should not be 0 if you're using a
variable-length data type.

It could be if the type is not marked toastable (ie, has storage class
PLAIN, which I think is the default even for varlena types).

But in any case I suspect that 90% of the problem here is an incorrect
declaration of the *function* not the type. We haven't seen the C
function declaration, nor the SQL CREATE FUNCTION command, but if it's
going through fmgr_oldstyle then there isn't a PG_FUNCTION_INFO_V1
marker, which maybe is the problem.

Thanks for your replies

Tom, you are correct. I missed PG_FUNCTION_INFO_V1 marker. After adding this
marker, my code works fine.
Thanks a lot.