Hi, BigTable is a NoSQL DB without join feature that you know in SQL. So you manage relations manually and do join by issuing several request instead a single one and you join within your application context. Basically you do more computation in your app than in the DB in this case. But the DB is more versatile and less contrained which is a big advantage sometimes.
Generally, you don't create normalized models in DB such as BigTable because you can't join. So you tend to denormalize your models (create join table) and use redundancy. In GAE, a great feature is the entity grouping where you can associate a child to a parent by its key but it has its limitations also. One thing to know is that, in the same transaction, you can target entities only in the same group of entities. One other thing to know is that when you fetch multiple entities in a row, the maximum returned number of entities is 1000 but you can manage it with offsets or better with cursors (look at GAE docs). There are a lot of other features but begin with that ;) regards Pascal PS: I'm lead developer of siena project providing a simple mapping layer for NoSQL/SQL (http://www.sienaproject.com) On Mon, Jul 25, 2011 at 8:09 PM, MK Z <v5s12.msc...@gmail.com> wrote: > Hi, > I'm pretty new to this GAE platffrom and the Google BigTable. Ive been > trying to search for tutorial (with example) on this subject but found > nothing to get me started (found handful of Python examples but my app > is to be written in Java). There are f in ew good examples which I have > tried and its working perfectly on GAE. As I come from RDBMS > background so im totally clueless on how "relationship" between tables > work as Google BigTable stores data differently. I also read > Programming Google App Engine book the example shown is not in-depth. > here is my scenario: If I have table department and employee, a > typical query will be select d.deptName, e.employee name, ... from > department d, employee e WHERE.... as far as my reading, this is not > supported in GQL. another thing, how do I do the data modelling? do I > need to use the mappedBy annotation? Any help will be appreciated. > > -- > You received this message because you are subscribed to the Google Groups > "Google App Engine" group. > To post to this group, send email to google-appengine@googlegroups.com. > To unsubscribe from this group, send email to > google-appengine+unsubscr...@googlegroups.com. > For more options, visit this group at > http://groups.google.com/group/google-appengine?hl=en. > > -- You received this message because you are subscribed to the Google Groups "Google App Engine" group. To post to this group, send email to google-appengine@googlegroups.com. To unsubscribe from this group, send email to google-appengine+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-appengine?hl=en.
