answers/opinions inline 2009/7/3 paweł kamiński <kami...@gmail.com>
> hi, all > I posted this on erlang-questions but I have no response from them so maybe > you can help clarify all this. > > recently I ve started to look at couchDB and what I see sounds great but I > have few general questions > > 1)when it is better to use document oriented db over RDMS or in your > opinion > it is always better to use couchDB:) When your data is schemaless it's better to use a schemaless DB. If your data would normally be stored in a document, then couchdb also seems like a good choice. > > 2)why schema free is good, how then ensure that what somebody puts to db is > what it should be especially when JSON can handle any data type and it is > easy to make a mistake Validation is a part of couchdb. You can write a validation function in javascript to ensure data integrity. > > > 3)as a old SQL developer Im force now to think how to implement all map and > reduce function to make them efficient. with select statement I just write > what I want and leave all to the system, dont I?. I'm sure as an old-sql developer you realize that if you write just any old query, it's not going to perform well. For example, querying by non-indexed columns is going to be a nightmare for performance. CouchDB views are indexed. Check out the wiki for more info about how couchdb views work. Here's an intro to the views http://wiki.apache.org/couchdb/Introduction_to_CouchDB_views > > > 4)how to design my db, curently my db is about 500 normilized tables, > master > to items tables, so I understand how to aggragate with MR but how to join > and how to make it work fast and use as small disk as possible and that > data > are not redundant. I understand that each document type is in separate REST > path and connect children to the document I should just put them to > path/docs/coffe/items. what about normalization and redundancy. Normalization is not something that document DBs concern themselves with. Often something you have multiple tables for will be one table in a well-designed document DB. Redundancy is often useful/necessary as well. I know this sounds terrible to a long-term RDBMS user. You've got to remember, this is a different world :). > > > 5)If my RDBS is running on 2core (ore sometimes one core) machine, and that > machine is alone server storing data from local clients is there any gain > of > using systems such as couchDB or others (ok replication and other features > are still nice) You'd have to benchmark your particular app to see if couchdb with a well-thought-out schema out-performed your RDBMS. For some tasks I'm sure it would. For others, perhaps not. If you're inserting a ton of documents, couchdb with its bulk insert would almost certainly outperform the RDBMS from what I understand, though I do not have benchmarks to show this. > > 6)this is somehow related to point 5) what scale down really means (to work > on mobiles, browsers etc)? If I have one core machine then will the system > be fast enough than RDMS (sqlite) Couch seems pretty light-weight. It runs great on my 5 year-old Ubuntu laptop. It is a dual core, but it only has 1 gig of RAM. > > > thanks for helping me in that > > pozdrawiam > Paweł Kamiński > > kami...@gmail.com > pkaminski....@gmail.com > ______________________ >
