See https://dev.monetdb.org/hg/MonetDB-extend/ for a tutorial on how to
create a UDF in C.  You can use the URL to clone from.

On 12/28/2016 09:28 PM, Alberto Ferrari wrote:
> Imad, I hope your success with this. Please comment if you get it, and
> then, could those new functions incorporate to future version of Monet?
> Or maybe easily compiled to current? So in the future users may suggest
> new useful functions (shame about SQL UDF performance)
>
> Regards!
>
> 2016-12-28 14:48 GMT-03:00 imad hajj chahine
> <imad.hajj.chahine@gmail.com <mailto:imad.hajj.chahine@gmail.com>>:
>
>     Hi,
>
>     After reviewing all the other alternatives like SQL and Python UDF,
>     I was either stuck on performance with SQL UDF or on usability with
>     Python UDF (unable to use with aggregation, and not such great
>     performance with dates),
>
>     so I decided to go the hard way with C functions, as a bonus it will
>     give me the possibility to change the functionalities without
>     worrying about dependencies, which was not the case in other languages.
>
>     The purpose is to create a set of formatting functions for Year,
>     Quarter, Month, Week and Day brackets, and of course i need to
>     create the bulk version of each function for performance.
>
>     Starting from the MTIMEdate_extract_year_bulk, now i have the simple
>     function working, and successfully calling it from mclient:
>     /
>     /
>     /str/
>     /UDFyearbracket(str *ret, const date *v)/
>     /{/
>     /if (*v == date_nil) {/
>     /*ret = GDKstrdup(str_nil);/
>     /} else {/
>     /int year;/
>     /fromdate(*v, NULL, NULL, &year);/
>     /*ret = (str) GDKmalloc(15);/
>     /sprintf(*ret, "%d", year);/
>     /}/
>     /return MAL_SUCCEED;/
>     /}/
>
>
>     For the bulk version i get an error in the log: gdk_atoms.c:1345:
>     strPut: Assertion `(v[i] & 0x80) == 0' failed.

>     /str/
>     /UDFBATyearbracket(bat *ret, const bat *bid)/
>     /{/
>     /BAT *b, *bn;/
>     /BUN i,n;/
>     /str *y;/
>     /const date *t;/
>     /
>     /
>     /if ((b = BATdescriptor(*bid)) == NULL)/
>     /throw(MAL, "UDF.BATyearbracket", "Cannot access descriptor");/
>     /n = BATcount(b);/
>     /
>     /
>     /bn = COLnew(b->hseqbase, TYPE_str, BATcount(b), TRANSIENT);/
>     /if (bn == NULL) {/
>     /BBPunfix(b->batCacheid);/
>     /throw(MAL, "UDF.BATyearbracket", "memory allocation failure");/
>     /}/
>     /bn->tnonil = 1;/
>     /bn->tnil = 0;/
>     /
>     /
>     /t = (const date *) Tloc(b, 0);/
>     /y = (str *) Tloc(bn, 0);/
>     /for (i = 0; i < n; i++) {/
>     /if (*t == date_nil) {/
>     /*y = GDKstrdup(str_nil);/
>     /} else/
>     /UDFyearbracket(y, t);/
>     /if (strcmp(*y, str_nil) == 0) {/
>     /bn->tnonil = 0;/
>     /bn->tnil = 1;/
>     /}/
>     /y++;/
>     /t++;/
>     /}/
>     /
>     /
>     /BATsetcount(bn, (BUN) (y - (str *) Tloc(bn, 0)));/
>     /
>     /
>     /bn->tsorted = BATcount(bn)<2;/
>     /bn->trevsorted = BATcount(bn)<2;/
>     /
>     /
>     /BBPkeepref(*ret = bn->batCacheid);/
>     /BBPunfix(b->batCacheid);/
>     /return MAL_SUCCEED;/
>     /}/
>

>     PS: I am not a c expert but i can find my way with basic operations
>     and pointers.
>
>     Any help or suggestions is appreciated.
>
>     Thank you.
>
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--
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