Re: C UDF

6 Jan 2017

      Hi Mark,

Is it possible to return Table or multiple columns from a C function?
Any example or existing function I can check in the code?

Also is it possible using a C function to expand table rows instead of
joining to a calendar table,
what i am trying to do is to expand a row and return an entry for each
month bracket between startdate and enddate?

Thanks

On Tue, Jan 3, 2017 at 4:45 PM, imad hajj chahine <
imad.hajj.chahine@gmail.com> wrote:
...
Thank you Mark,
I should refresh my memory about C programming, I never thought i would
code in C again.
On Tue, Jan 3, 2017 at 3:48 PM, Mark Raasveldt  wrote:
...
Hey Imad,
No, it does not apply to integers because you are not doing any heap
allocation.
Mark
On 02 Jan 2017, at 19:03, imad hajj chahine 
wrote:
Mark,
Does the same apply for Integer values, Meaning its better to declare one
the int value and used in all the iteration, do I have a performance issue
with the following code:
str
UDFyearlag(int *ret, const date *v1, const date *v2)
{
if (*v1 == date_nil || *v2 == date_nil) {
*ret = int_nil;
} else {
int y1 = 0, y2 = 0;
fromdate(*v1, NULL, NULL, &y1);
fromdate(*v2, NULL, NULL, &y2);
*ret = y2 - y1;
}
return MAL_SUCCEED;
}
str
UDFBATyearlag(bat *ret, const bat *bid1, const bat *bid2)
{
BAT *b1, *b2, *bn;
BATiter bi1, bi2;
BUN i,n;
b1 = BATdescriptor(*bid1);
b2 = BATdescriptor(*bid2);
if (b1 == NULL || b2 == NULL) {
if (b1)
BBPunfix(b1->batCacheid);
if (b2)
BBPunfix(b2->batCacheid);
throw(MAL, "UDF.BATyearlag", "Cannot access descriptor");
}
n = BATcount(b1);
bn = COLnew(b1->hseqbase, TYPE_int, BATcount(b1), TRANSIENT);
if (bn == NULL) {
BBPunfix(b1->batCacheid);
BBPunfix(b2->batCacheid);
throw(MAL, "UDF.BATyearlag", "memory allocation failure");
}
bi1 = bat_iterator(b1);
bi2 = bat_iterator(b2);
BATloop(b1, i, n) {
int y;
const date *t1 = (const date *) BUNtail(bi1, i);
const date *t2 = (const date *) BUNtail(bi2, i);
if (*t1 == date_nil || *t2 == date_nil) {
y = int_nil;
} else
UDFyearlag(&y, t1, t2);
if (BUNappend(bn, &y, 0) != GDK_SUCCEED) {
goto bailout;
}
}
BBPkeepref(*ret = bn->batCacheid);
BBPunfix(b1->batCacheid);
BBPunfix(b2->batCacheid);
return MAL_SUCCEED;
  bailout:
BBPunfix(b1->batCacheid);
BBPunfix(b2->batCacheid);
BBPunfix(bn->batCacheid);
throw(MAL, "UDF.BATyearlag", MAL_MALLOC_FAIL);
}
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