Re: C UDF

28 Dec 2016

      Thank you Sjoerd,

Any idea how to convert an integer to UTF-8 string, does sprintf come with
a variation that can handle UTF-8?

Thank you.

On Wed, Dec 28, 2016 at 11:08 PM, Sjoerd Mullender 
wrote:
...
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
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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