Обсуждение: Return setof values from C-function

On Tue, Dec 10, 2013 at 1:30 AM, Yuriy Rusinov <yrusinov@gmail.com> wrote:
> Dear Colleagues !
>
> I have to return setof values from C-function
>
> I wrote
>
>     FuncCallContext *funcctx;
>     int call_cntr;
>     int max_calls;
>     AttInMetadata *attinmeta;
>     unsigned long il;
>     if (SRF_IS_FIRSTCALL())
>     {
>         MemoryContext   oldcontext;
>         funcctx = SRF_FIRSTCALL_INIT();
>         oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
>         funcctx->max_calls = num;
>         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")));
>         attinmeta = 0;//TupleDescGetAttInMetadata(tupdesc);
>         funcctx->attinmeta = 0;//attinmeta;
>         MemoryContextSwitchTo(oldcontext);
>         funcctx->tuple_desc = BlessTupleDesc( tupdesc );
>         elog (INFO, "1st row");
>     }
>     funcctx = SRF_PERCALL_SETUP();
>     call_cntr = funcctx->call_cntr;
>     max_calls = funcctx->max_calls;
>     attinmeta = funcctx->attinmeta;
>     HeapTuple tuple;
>     if (call_cntr < max_calls)
>     {
>         elog (INFO, "Rows");
>         unsigned long il = call_cntr;
>         Datum * hvalues = (Datum *)palloc (2*sizeof(Datum));
>         double val = gsl_histogram_get (gHist, il);
>         hvalues[0] = UInt32GetDatum (il);
>         hvalues[1] = Float8GetDatum (val);
>         bool * nulls = palloc( 2 * sizeof( bool ) );
>
>         elog (INFO, "%lu", il);
>         tuple = heap_form_tuple( tupdesc, hvalues, nulls);
>         elog (INFO, "%lu", il);
>         //BuildTupleFromCStrings (attinmeta, hvalues);
>         pfree (nulls);
>         pfree (hvalues);
>         SRF_RETURN_NEXT(funcctx, HeapTupleGetDatum( tuple ) );
>     }
>     else
>     {
>         SRF_RETURN_DONE(funcctx);
>     }
> as written in documentation, but my function drops on
> tuple = heap_form_tuple( tupdesc, hvalues, nulls);
> Could you tell me, are there any errors ?

Where is 'tupdesc' coming from.  Don't you need to copy it from the
function context?

merlin

On Tue, Dec 10, 2013 at 9:44 AM, Yuriy Rusinov <yrusinov@gmail.com> wrote:
> I have added code
>
>         Oid * oids = (Oid *)palloc (2*sizeof (Oid));
>         oids[0] = INT8OID;
>         oids[1] = FLOAT8OID;
>         if (get_call_result_type(fcinfo, oids, &tupdescRes) !=
> TYPEFUNC_COMPOSITE)
>             ereport(ERROR,
>                     (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
>                      errmsg("function returning record called in context "
>                             "that cannot accept type record")));
>
> and try to obtain tupdescRes  from get_call_result_type function, before
> this I do
>
> create type hist_point as (inum bigint, bin float8);
>  and
> create or replace function histogram (varchar, float8, float8, int4) returns
> setof hist_point
>     as '$libdir/libfloader.so', 'histogram' language 'c' strict security
> definer;
>
> but the result does not obtained.

what error are you getting?  Also, I think you are not properly
initializing NULLs array -- that could be your issue.

merlin