result properties in pcre.c
Hi, I was looking at pcre.c for some inspiration and found something suspicious. At the end of both pcre_likeselect() and re_likeselect(): if (bn && !msg) { BATsetcount(bn, BATcount(bn)); /* set some properties */ bn->tsorted = true; bn->trevsorted = bn->batCount <= 1; bn->tkey = true; bn->tseqbase = bn->batCount == 0 ? 0 : bn->batCount == 1 ? * (oid *) Tloc(bn, 0) : oid_nil; } Which I read as: if everything went well, then the result is sorted and key. But I miss why it should be sorted and key. Roberto
On 24/08/2020 19.43, Roberto Cornacchia wrote:
Hi, I was looking at pcre.c for some inspiration and found something suspicious.
At the end of both pcre_likeselect() and re_likeselect():
if (bn && !msg) { BATsetcount(bn, BATcount(bn)); /* set some properties */ bn->tsorted = true; bn->trevsorted = bn->batCount <= 1; bn->tkey = true; bn->tseqbase = bn->batCount == 0 ? 0 : bn->batCount == 1 ? * (oid *) Tloc(bn, 0) : oid_nil; }
Which I read as: if everything went well, then the result is sorted and key. But I miss why it should be sorted and key.
They are sorted because of the way the BAT is created. Remember, a select returns a "candidate list", an ordered list of matching OIDs. The list is created by going through the OIDs of the to-be-selected bat and adding the OID to the result when there is a match.
Roberto
_______________________________________________ users-list mailing list users-list@monetdb.org https://www.monetdb.org/mailman/listinfo/users-list
-- Sjoerd Mullender
Of course, silly me. I was forgetting that it returns a candidate list.
Thanks Sjoerd
On Tue, 25 Aug 2020, 08:54 Sjoerd Mullender,
On 24/08/2020 19.43, Roberto Cornacchia wrote:
Hi, I was looking at pcre.c for some inspiration and found something suspicious.
At the end of both pcre_likeselect() and re_likeselect():
if (bn && !msg) { BATsetcount(bn, BATcount(bn)); /* set some properties */ bn->tsorted = true; bn->trevsorted = bn->batCount <= 1; bn->tkey = true; bn->tseqbase = bn->batCount == 0 ? 0 : bn->batCount == 1 ? * (oid *) Tloc(bn, 0) : oid_nil; }
Which I read as: if everything went well, then the result is sorted and key. But I miss why it should be sorted and key.
They are sorted because of the way the BAT is created. Remember, a select returns a "candidate list", an ordered list of matching OIDs. The list is created by going through the OIDs of the to-be-selected bat and adding the OID to the result when there is a match.
Roberto
_______________________________________________ users-list mailing list users-list@monetdb.org https://www.monetdb.org/mailman/listinfo/users-list
-- Sjoerd Mullender _______________________________________________ users-list mailing list users-list@monetdb.org https://www.monetdb.org/mailman/listinfo/users-list
participants (2)
-
Roberto Cornacchia -
Sjoerd Mullender