Обсуждение: forming tuple as an attribute inside another tuple in c function

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forming tuple as an attribute inside another tuple in c function

От
Marios Vodas
Дата:
Is it posible? Either by using heap_form_tuple or BuildTupleFromCStrings.

CREATE TYPE p_type AS
(
x double precision,
y double precision
);
CREATE TYPE d_type AS
(
i p_type,
e p_type,
id integer
);

CREATE OR REPLACE FUNCTION demo()
RETURNS d_type
AS '/home/user/PostgreSQL/9.0/lib/mylib','demo'
LANGUAGE C STRICT;

Datum demo(PG_FUNCTION_ARGS) {
    float8 xi = 1;
    float8 yi = 2;

    float8 xe = 3;
    float8 ye = 4;

    int32 id = 1;

    bool isnull;

    TupleDesc tupdesc;
    Datum values[3];
    HeapTuple tuple;

    if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE) {
        ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("function returning record called in context that cannot accept type record")));
    }

    BlessTupleDesc(tupdesc);

    values[0] = ?;                                             //how?
    values[1] = ?;                                             //how?
    values[2] = Int32GetDatum(id);

    tuple = heap_form_tuple(tupdesc, values, &isnull);

    PG_RETURN_DATUM(HeapTupleGetDatum(tuple));
}

Re: forming tuple as an attribute inside another tuple in c function

От
Tom Lane
Дата:
Marios Vodas <mvodas@gmail.com> writes:
> Is it posible? Either by using heap_form_tuple or BuildTupleFromCStrings.

heap_form_tuple followed by HeapTupleGetDatum should work; that's what's
done in ExecEvalRow() for instance.  You've omitted to tell us just
what's going wrong for you.
        regards, tom lane

Re: forming tuple as an attribute inside another tuple in c function

От
Marios Vodas
Дата:
OK but what is the recommended way to get TupleDesc for p_type? I am aware of RelationNameGetTupleDesc but I shouldn't use it since it is deprecated.
However by using it the code would look something like this (I tested it and it works as expected):

Datum demo(PG_FUNCTION_ARGS) {
    float8 xi = 1;
    float8 yi = 2;

    float8 xe = 3;
    float8 ye = 4;

    int32 id = 1;

    bool isnull;

    TupleDesc tupdesc;
    TupleDesc tupdesc_p;

    Datum values[3];
    Datum vi[2];
    Datum ve[2];

    HeapTuple tuple;
    HeapTuple i;
    HeapTuple e;

    tupdesc_p = RelationNameGetTupleDesc("p_type");

    vi[0] = Float8GetDatum(xi);
    vi[1] = Float8GetDatum(yi);
    i = heap_form_tuple(tupdesc_p, vi, &isnull);

    ve[0] = Float8GetDatum(xe);
    ve[1] = Float8GetDatum(ye);
    e = heap_form_tuple(tupdesc_p, ve, &isnull);

    if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE) {
        ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("function returning record called in context that cannot accept type record")));
    }

    BlessTupleDesc(tupdesc);

    values[0] = HeapTupleGetDatum(i);
    values[1] = HeapTupleGetDatum(e);
    values[2] = Int32GetDatum(id);

    tuple = heap_form_tuple(tupdesc, values, &isnull);

    PG_RETURN_DATUM(HeapTupleGetDatum(tuple));
}

On Mon, Sep 27, 2010 at 3:32 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
You've omitted to tell us just
what's going wrong for you.

                       regards, tom lane

Re: forming tuple as an attribute inside another tuple in c function

От
Robert Haas
Дата:
On Mon, Sep 27, 2010 at 2:52 AM, Marios Vodas <mvodas@gmail.com> wrote:
> OK but what is the recommended way to get TupleDesc for p_type?

It's mentioned in the documentation...

http://www.postgresql.org/docs/current/static/xfunc-c.html#AEN47214

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