From: | Marios Vodas <mvodas(at)gmail(dot)com> |
---|---|
To: | pgsql-hackers(at)postgresql(dot)org |
Subject: | C function to return tuple |
Date: | 2010-09-26 15:35:10 |
Message-ID: | AANLkTi=U63_AgNUfPxrJKU4MEz0mJXgvss74s5OHO1m=@mail.gmail.com |
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Lists: | pgsql-hackers |
I have these types:
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 d_swap(d_type)
RETURNS d_type
AS '/home/user/PostgreSQL/9.0/lib/mylib','d_swap'
LANGUAGE C STRICT;
My problem is that I don't know how to construct the d_type tuple in the c
function. I read the documentation but it only explains how i could do that
for a more simple type like p_type.
The difficulty is that d_type has attributes of p_type.
Thank you in advance.
This is the c code I wrote until now:
Datum d_swap(PG_FUNCTION_ARGS) {
HeapTupleHeader t = PG_GETARG_HEAPTUPLEHEADER(0);
HeapTupleHeader i;
HeapTupleHeader e;
bool isnull;
TupleDesc tupdesc;
Datum values[3];
HeapTuple tuple;
int tuplen;
bool *nulls;
i = DatumGetHeapTupleHeader(GetAttributeByName(t, "i", &isnull));
e = DatumGetHeapTupleHeader(GetAttributeByName(t, "e", &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] = e;
values[1] = i;
values[2] = GetAttributeByName(t, "id", &isnull);
tuplen = tupdesc->natts;
nulls = palloc(tuplen * sizeof (bool));
tuple = heap_form_tuple(tupdesc, values, nulls);
pfree(nulls);
PG_RETURN_DATUM(HeapTupleGetDatum(tuple));
}
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