Hello,
i want write functions like this:
CREATE FUNCTION foo(text) returns real as '<path>/foo.dll', 'foo' LANGUAGE C STRICT;"
CREATE FUNCTION foo2(text) returns table(c1 text, c2 int) as '<path>/foo2.dll', 'foo' LANGUAGE C STRICT;
So far, so clear. I don't want to return one scalar value or SETOF smth, I want to start the function like this:
select * from foo; … and the rows will be returned.
I read the chapter
https://www.postgresql.org/docs/11/spi.html
and especially
again and again but I found no solution. So, the functions should return rows of data not just „one“ result or composite types.
The documentation regarding usable examples are very sparse, so I found and tried with this pice of code:
ArrayType* pg_array = DatumGetArrayTypeP(_row_val);
c_array = (float *)ARR_DATA_PTR(pg_array);
pg_array_size = ARR_DIMS(pg_array)[0];
—> so it’s clear how do I get my data via SPI* functionalty, the result set is within the pg_array or the casted c_array.
I found this within funcapi.h:
/* Type categories for get_call_result_type and siblings */
typedef enum TypeFuncClass
{ TYPEFUNC_SCALAR, /* scalar result type */ TYPEFUNC_COMPOSITE, /* determinable rowtype result */ TYPEFUNC_COMPOSITE_DOMAIN, /* domain over determinable rowtype result */ TYPEFUNC_RECORD, /* indeterminate rowtype result */ TYPEFUNC_OTHER /* bogus type, eg pseudotype */
} TypeFuncClass;
and tried:
TupleDesc tupdesc;
HeapTuple tuple;
Datum rs[100];
int tuplen;
bool nulls;
if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_RECORD) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("function returning record called in context " "that cannot accept type record")));
BlessTupleDesc(tupdesc);
for (int j = 0; j < 100; j++) { rs[j] = Float8GetDatum(c_array[j]);
}
tuplen = tupdesc->natts;
nulls = palloc(tuplen * sizeof(bool));
tuple = heap_form_tuple(tupdesc, rs, nulls);
pfree(nulls);
SPI_finish();
PG_RETURN_DATUM(HeapTupleGetDatum(tuple));
But it doesn’t work. Either the get_call_result_type fails because the function definition doesn’t match or the the client process crashes because smth. happens and I don’t know how this stuff should work.
So, due to the lack of examples in general and the sparse documentation about it, any help will be appreciate.
Thanks.
