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Thread: Return setof values from C-function

Return setof values from C-function

From

Yuriy Rusinov

Date:

10 December 2013, 07:31:06

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 ?

--
Best regards,
Sincerely yours,
Yuriy Rusinov.

Re: Return setof values from C-function

From

Merlin Moncure

Date:

10 December 2013, 15:33:59

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

Re: Return setof values from C-function

From

Yuriy Rusinov

Date:

10 December 2013, 15:44:39

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.

On Tue, Dec 10, 2013 at 7:33 PM, Merlin Moncure <mmoncure@gmail.com> wrote:

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

--
Best regards,
Sincerely yours,
Yuriy Rusinov.

Re: Return setof values from C-function

From

Merlin Moncure

Date:

10 December 2013, 15:57:18

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

Re: Return setof values from C-function

From

Yuriy Rusinov

Date:

11 December 2013, 08:46:30

I have received an error

The connection to the server was lost. Attempting reset: Failed

This problem was solved using by C-strings instead of Datum

such as

FuncCallContext *funcctx;

int call_cntr;

int max_calls;

AttInMetadata *attinmeta;

unsigned long il;

TupleDesc tupdescRes;

gsl_histogram * gHist;

if (SRF_IS_FIRSTCALL())

{

size_t nr_rand = strlen ( VARDATA (PG_GETARG_VARCHAR_P(0)));

char * sql = (char *) palloc (nr_rand+1);

// strncpy (sql, (char *)PG_GETARG_VARCHAR_P(0), nr_rand);

snprintf (sql, nr_rand+1, "%s", VARDATA (PG_GETARG_VARCHAR_P (0)));

float8 xmin = PG_GETARG_FLOAT8 (1);

float8 xmax = PG_GETARG_FLOAT8 (2);

unsigned int num = PG_GETARG_UINT32(3);

//float8 * result = (float8 *) (palloc (sizeof(float8)));

//*result= 5.0;

gHist = gsl_histogram_alloc (num);

elog (INFO, "query = %s\n", sql);

gsl_histogram_set_ranges_uniform (gHist, (double)xmin, (double)xmax);

// Datum d = PointerGetDatum (gHist);

SPI_connect ();

int retVal = SPI_execute (sql, true, 0);

if (retVal != SPI_OK_SELECT)

{

elog (ERROR, "Cannot load values");

SPI_finish ();

PG_RETURN_NULL();

}

elog (INFO, "%d\n", retVal);

unsigned long int nproc = SPI_processed;

elog (INFO, "number of points is %lu, number of bins is %u", nproc, num);

// SPI_finish ();

// pfree (sql);

// PG_RETURN_NULL();

int i=0;

TupleDesc tupdesc = SPI_tuptable->tupdesc;

for (; i< nproc; i++)

{

HeapTuple tuple = SPI_tuptable->vals[i];

int ncolbuf = 1;

char * x_str = SPI_getvalue (tuple, tupdesc, ncolbuf);

if (!x_str)

continue;

double x= atof (x_str);

//elog (INFO, "value=%f", x);

int res = gsl_histogram_increment (gHist, x);

if (res != 0)

{

elog (NOTICE, "Range error, value is %lf, min value is %lf, max value %lf", x, gsl_histogram_min(gHist), gsl_histogram_max (gHist) );

continue;

}

SPI_finish ();

pfree (sql);

elog (INFO, "Reading was completed\n");

MemoryContext oldcontext;

funcctx = SRF_FIRSTCALL_INIT();

oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);

funcctx->max_calls = num;

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")));

attinmeta = TupleDescGetAttInMetadata(tupdescRes);

funcctx->attinmeta = attinmeta;

MemoryContextSwitchTo(oldcontext);

//funcctx->tuple_desc = BlessTupleDesc( tupdescRes );

pfree (oids);

elog (INFO, "1st row");

}

funcctx = SRF_PERCALL_SETUP();

call_cntr = funcctx->call_cntr;

max_calls = funcctx->max_calls;

elog (INFO, "number of rows = %d, number of columns are %d", max_calls, tupdescRes->natts );

attinmeta = funcctx->attinmeta;

HeapTuple tuple;

if (call_cntr < max_calls)

{

elog (INFO, "Rows");

il = call_cntr;

//Datum * hvalues = (Datum *)palloc (2*sizeof(Datum));

char ** svals = (char **) palloc (2*sizeof (char*));

svals [0] = (char *) palloc(5 * sizeof(char));

svals [1] = (char *) palloc(20 * sizeof(char));

double val = gsl_histogram_get (gHist, il);

snprintf (svals[0], 5, "%lu", il);

snprintf (svals[1], 20, "%lf", val);

//hvalues[0] = UInt32GetDatum (il);

//hvalues[1] = Float8GetDatum (val);

bool * nulls = palloc( 2 * sizeof( bool ) );

elog (INFO, "%lu", il);

tuple = BuildTupleFromCStrings (attinmeta, svals);//heap_form_tuple( tupdescRes, hvalues, nulls);

elog (INFO, "%lu", il);

Datum result = HeapTupleGetDatum(tuple);

pfree (nulls);

pfree (svals[1]);

pfree (svals[0]);

pfree (svals);

//pfree (hvalues);

SRF_RETURN_NEXT(funcctx, result);//HeapTupleGetDatum( tuple ) );

}

else

{

SRF_RETURN_DONE(funcctx);

}

Thanks a lot.

Yuriy Rusinov