If a column is indexed with binary encoding, you should be able to answer this kind of query within the index by combining the corresponding bitvectors. Would that be more efficient than scanning the data directly as described? I guess it is a function of the size of the WAH compressed bitvectors to interrogate.
Andrew On Jul 12, 2012, at 3:09 AM, "Lidawei (Davey)" <[email protected]<mailto:[email protected]>> wrote: Hi Petr, I think what you want is “WHERE (flags & 0x1001) == 0x1001”, if you want ALL flags be true. Then “WHERE (flags & 0x1001)!=0”, if you want ANY flag be true In my scenario, 8 bit flag is not enough :-( Hope John can realize a more long bit stream… Cheers, Davey Date: Mon, 9 Jul 2012 10:02:10 +0200 From: Thorgrin <[email protected]<mailto:[email protected]>> Subject: Re: [FastBit-users] Is it possible to eliminate the rescursion of ibis::qExpr::simplify To: FastBit Users <[email protected]<mailto:[email protected]>> Cc: "K. John Wu" <[email protected]<mailto:[email protected]>> Message-ID: <CALbOe5PmsL_kRSydgSx=8kzxw05emj6fdfhykuw3-lhlhqm...@mail.gmail.com<mailto:CALbOe5PmsL_kRSydgSx=8kzxw05emj6fdfhykuw3-lhlhqm...@mail.gmail.com>> Content-Type: text/plain; charset=UTF-8 Hi John, just skipping through the FastBit mail conference, this email caught my eye. I would greatly appreciate the bit operator feature. In our scenario we are using BYTE to store TCP flags values. But it makes it impossible to ask for value of a specific bit regardless of the others. If I was able to use something like "WHERE flags & 1001" (binary of decimal), it would be really great. Regards, Petr _______________________________________________ FastBit-users mailing list [email protected]<mailto:[email protected]> https://hpcrdm.lbl.gov/cgi-bin/mailman/listinfo/fastbit-users _______________________________________________ FastBit-users mailing list [email protected] https://hpcrdm.lbl.gov/cgi-bin/mailman/listinfo/fastbit-users
