Makes sense, use a get_slice() against the second row and pass in the column names. Should e fine.
If you run into performance issues look at slice_buffer_size and column_index_size in the config. Aaron On 9/02/2011, at 5:16 AM, Aklin_81 <asdk...@gmail.com> wrote: > Amongst two rows, where I need to find the common columns. I will not > have more than 200 columns(in 99% cases) for the 1st row. But the 2nd > row where I need to find these columns may have even around a million > valueless columns. > > A point to note is:- These calculations are all done for **writing the > data to the database that has been collected from presentation layer** > & not while presentation of data. > > I am using the results of such intersection to find the rows(that are > pointed by names of common columns) that I should write to. The > calculations are done after a Post is submitted by a user, in a > discussions forum. Actually this is used to find out the mutual > connections in a group & write to the rows pointed by common columns. > 1st row represents the connection list of a user, which is not going > to be more than 100-250 columns for my case & 2nd row represents the > members of a group which may contain a million columns as I told. > I find the mutual connections in a group(by finding the common columns > in the above two rows) and then write to the rows of those users. > > Cant I run a batch query to ask for all columns that I picked up from > 1st row and want to ask in the 2nd row ?? > > Is there any better way ? > > Asil > > >> >> On Feb 7, 2011, at 12:30 AM, Aklin_81 wrote: >> >>> Thanks Aaron & Shaun, >>> >>> ****************************** >>> I think my question might have been unclear to some of you. So I would >>> again explain my problem(& solution which I thought of) for the sake >>> of clarity:- >>> >>> Consider I have 2 rows. 1st row contains 60-70 columns and 2nd row >>> contains like in hundreds of thousands columns. Both the columns sets >>> are all valueless. I need to just findout the **common column names** >>> in the two rows. **These two rows are known to me**. So what I plan to >>> do is, I just pick up all **columns (names)** of 1st row (60 -70 >>> columns) and just ask for them in 2nd row, whatever column names I get >>> back is my result. >>> Would there be any problem with this solution ? This is how I am >>> expecting to get common column names. >>> >>> Please do not consider it as a JOIN case as it leads to unnecessary >>> confusions, I just need common column names from valueless columns in >>> the two rows. >>> >>> ******************************** >>> >>> Aaron, actually the intersection data is very much context based. So >>> say if there are 10 million rows in CF A & 1 million in CF B, then >>> intersection data would be containing 10 million *1 million rows. This >>> would involve very huge & unaffordable amounts of denormalization. >>> And finding columns in client would require pulling unnecessary >>> columns like pulling 100,000 columns from a row of which only 60-70 >>> are required . >>> >>> Shaun, I hope my above clarification has clarified things a bit. Yes, >>> the rows, of which I need to find common columns are known to me. >>> >>> >>> Thank you all, >>> Asil >>> >>> >>> On Mon, Feb 7, 2011 at 3:53 AM, Shaun Cutts <sh...@cuttshome.net> wrote: >>>> In theory, you should be able to do joins by creating an extra column in >>>> one column family, holding the "foreign key" of the matching row in the >>>> other family. >>>> >>>> This assumes that the info you are joining on is available in both CFs (is >>>> not some sort of functional transformation). >>>> >>>> I have just found that the implementation for secondary indexes is not yet >>>> very close to optimal for more complex "joins" involving multiple indexes, >>>> I'm not sure if that affects you as you didn't say what you are joining on. >>>> >>>> -- Shaun >>>> >>>> >>>> On Feb 6, 2011, at 4:22 PM, Aaron Morton wrote: >>>> >>>>> Is it possible for you to dernormalise and write all the intersection >>>>> values? Will depend on how many I guess. >>>>> >>>>> The other alternative is to pull back more data that you need and the >>>>> intersection in code in the client. >>>>> >>>>> >>>>> Hope that helps. >>>>> Aaron >>>>> On 7/02/2011, at 7:11 AM, Aklin_81 <asdk...@gmail.com> wrote: >>>>> >>>>>> Hi, >>>>>> >>>>>> @buddhasystem : yes that's well known solution. But obviously when >>>>>> mysql couldnt satisfy my needs, I am here. My question is in context >>>>>> of Cassandra, if it possible to achieve intersection result set of >>>>>> columns in two rows, by the way I spoke about. >>>>>> >>>>>> @Edward: yes that I know but how does that fit here for obtaining the >>>>>> common columns among two rows. >>>>>> >>>>>> Thanks for your comments.. >>>>>> >>>>>> -Asil >>>>>> >>>>>> >>>>>> On Sun, Feb 6, 2011 at 9:55 PM, Edward Capriolo <edlinuxg...@gmail.com> >>>>>> wrote: >>>>>>> On Sun, Feb 6, 2011 at 10:15 AM, buddhasystem <potek...@bnl.gov> wrote: >>>>>>>> >>>>>>>> Hello, >>>>>>>> >>>>>>>> If the amount of data is _that_ small, you'll have a much easier life >>>>>>>> with >>>>>>>> MySQL, which supports the "join" procedure -- because that's exactly >>>>>>>> what >>>>>>>> you want to achieve. >>>>>>>> >>>>>>>> >>>>>>>> asil klin wrote: >>>>>>>>> >>>>>>>>> Hi all, >>>>>>>>> >>>>>>>>> I want to procure the intersection of columns set of two rows (from 2 >>>>>>>>> different column families). >>>>>>>>> >>>>>>>>> To achieve the intersection results, Can I, first retrieve all >>>>>>>>> columns(around 300) from first row and just query by those column >>>>>>>>> names in the second row(which contains maximum 100 000 columns) ? >>>>>>>>> >>>>>>>>> I am using the results during the write time & not before presentation >>>>>>>>> to the user, so latency wont be much concern while writing. >>>>>>>>> >>>>>>>>> Is it the proper way to procure intersection results of two rows ? >>>>>>>>> >>>>>>>>> Would love to hear your comments.. >>>>>>>>> >>>>>>>>> >>>>>>>>> --------- >>>>>>>>> >>>>>>>>> Regards, >>>>>>>>> Asil >>>>>>>>> >>>>>>>>> >>>>>>>> >>>>>>>> -- >>>>>>>> View this message in context: >>>>>>>> http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/Finding-the-intersection-results-of-column-sets-of-two-rows-tp5997248p5997743.html >>>>>>>> Sent from the cassandra-u...@incubator.apache.org mailing list archive >>>>>>>> at Nabble.com. >>>>>>>> >>>>>>> >>>>>>> You can use multi-get when fetching lists of already know keys >>>>>>> optimize your round rip time. >>>>>>> >>>> >>>> >> >>
