Hi Julian, Say I have a cube which has many dimensions, among them there are 3 dimensions: "country", "state", "city"; As we know, these three dimensions are a hierarchy, so in the past we would suggest user to declare them as a "hierarchy" relationship in Kylin, then Kylin will calculate the following combinations (for these 3 dimensions):
* country country, state country, state, city Using "hierarchy" helps to reduce the combinations from 2^3 to 4, this is good; While, my report or dashboard will group by (or filter on) all these 3 dimensions when doing location-based analysis; this means some combinations with "hierarchy" are usless; In this case, I would declare them as a "joint", then Kylin will calculation these combinations (for these 3 dimensions): * country, state, city You can see now the combination number is 2, that's a further optimization on "hierarchy", quite simple and effective. Hope this can help. 2016-07-02 0:20 GMT+08:00 Julian Hyde <[email protected]>: > A real(ish) world example would help me understand. Can you give an > example of a joint dimension in terms of sales, customers, products, etc.? > > On Jul 1, 2016, at 2:01 AM, ShaoFeng Shi <[email protected]> wrote: > > "joint" just tell Kylin to prune certain combinations; for example, "joint > AB" will prune all combinations that only has A or only has B; the order in > "joint" doesn't matter; > > for case 3), it should not be allowed on Kylin's GUI, can you verify? > > > > 2016-07-01 14:47 GMT+08:00 Richard Calaba (Fishbowl) <[email protected] > >: > >> Ok, so AB are joined, if: >> >> >> >> 1) *Both* A and B have to be specified in either in WHERE-clause or >> GROUP BY-clause ; or one in WHERE and the other in GROUP-BY >> >> >> >> 2) The order of the Joint Dimension is or is NOT important ??? If >> AB is joint, then BA is also joint, right? >> >> >> >> Meaning "select ... group by B, A" or "select ... where B = xx group by >> A" is also valid for AB as joint-dimension ??? >> >> >> >> 3) If AB is joint and AC is joint: >> >> a. It does NOT mean that ABC is necessarily joint group, right ??? >> >> >> b. Also BC doesn’t have to be joint, correct ?? >> >> >> >> Thanx, Richard. >> >> >> >> *From:* ShaoFeng Shi [mailto:[email protected]] >> *Sent:* Thursday, June 30, 2016 7:45 PM >> *To:* [email protected] >> *Subject:* Re: Joint VS Derived >> >> >> >> This slide has introduction on the Derived Dim: >> http://www.slideshare.net/YangLi43/design-cube-in-apache-kylin >> >> >> >> "Joint" is introduced since 1.5.1; Using "joint" to combine multiple >> dimensions into "one" ; Say if you have Dim A, B, C; among them AB are >> always appeared together, e.g, "select ... group by A, B" or "select ... >> where A = xx group by B"; in this case you can declare AB as "joint"; for >> Kylin it looks like a 2 dim cube: AB, C, the combinations are decreased >> from 2^3 to 2^2; >> >> >> >> 2016-06-30 6:56 GMT+08:00 Alberto Ramón <[email protected]>: >> >> Hi >> >> I don't understand the difference between: >> >> - Joint Dim (from Dimension Step ) >> - Derived Dim (from Advance Setings Step) >> >> Some example ? :) >> >> >> >> >> >> -- >> >> Best regards, >> >> >> >> Shaofeng Shi >> >> >> >> No virus found in this message. >> Checked by AVG - www.avg.com >> Version: 2016.0.7640 / Virus Database: 4613/12530 - Release Date: 07/01/16 >> > > > > -- > Best regards, > > Shaofeng Shi > > > -- Best regards, Shaofeng Shi
