I don't think this is very useful for column names. I could see it being useful for values but if we're going to add predicate queries then I'd rather do something more general.
2010/2/1 Ted Zlatanov <t...@lifelogs.com>: > On Mon, 1 Feb 2010 09:42:16 -0600 Jonathan Ellis <jbel...@gmail.com> wrote: > > JE> 2010/2/1 Ted Zlatanov <t...@lifelogs.com>: >>> On Fri, 29 Jan 2010 15:07:01 -0600 Ted Zlatanov <t...@lifelogs.com> wrote: >>> > TZ> On Fri, 29 Jan 2010 12:06:28 -0600 Jonathan Ellis <jbel...@gmail.com> > wrote: > JE> On Fri, Jan 29, 2010 at 9:09 AM, Mehar Chaitanya > JE> <meharchaita...@gmail.com> wrote: >>>>>> 1. This would lead to enourmous amount of duplication of data, in short >>>>>> if I now want to view the data from IS_PUBLISHED dimenstion then my >>>>>> database >>>>>> size would scale up tremendously. >>> > JE> Yes. But disk space is so cheap it's worth using a lot of it to make > JE> other things fast. >>> > TZ> IIUC, Mehar would be duplicating the article data for every article tag. >>> > TZ> I searched the bug tracker and wiki and didn't find anything on the > TZ> topic of tag storage and search, so I don't think Cassandra supports > TZ> tags without data duplication. >>> > TZ> Would it be possible to implement an optional byte[] bitmap field in > TZ> SliceRange? If you can specify the bitmap as an optional field it would > TZ> not break current clients. Then the search can return only the subset > TZ> of the range that matches the bitmap. This would make sense for > TZ> BytesType and LongType, at least. >>> >>> I looked at the source code and it seems that >>> StorageProxy::getSliceRange() is the focal point for reads and bitmap >>> matching should be implemented there. The bitmap could be applied as a >>> filter before the other SliceRange parameters, especially the max number >>> of return results. It may be worth the effort to send the bitmap down >>> to the ReadCommand/ColumnFamily level to reduce the number of potential >>> matches. >>> >>> If this is not feasible for technical reasons I'd like to know. >>> Otherwise I'll put it on my TODO list and produce a proposal (unless >>> someone more knowledgeable is interested, of course). > > JE> how would this be different then the byte[] column name you can > JE> already match on? > > Given byte columns > > A 0110 > B 0111 > C 0101 > > the bitmask approach would let you specify a bitmask of "0011" and get > only B. It's just an AND that looks for a non-zero value. So you can > say "0111" and get A, B, and C. Or "0010" to get A and B. "1000" gets > nothing. > > Cassandra could support OR-ed multiples for better queries, so you could > ask for (0001,0010) to get A, B, and C. > > Ted > >
